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Morning (Fasting) Vs. Afternoon Resistance Exercise in Individuals with Type 1 Diabetes: A Randomized Cross-Over Study
Abstract
Objective:
To determine the effect of morning exercise in fasting condition, versus afternoon exercise on blood glucose responses to resistance exercise (RE).
Research design and methods:
Using a randomized crossover design, 12 participants with type 1 diabetes [9 females, aged 31 ± 8.9 years, diabetes duration 19.1 ± 8.3 years, HbA1c = 7.4 ± 0.8% (57.4 ± 8.5 mmol/mol)] performed ∼40 minutes of RE (three sets of eight repetitions, seven exercises, at the individual's pre-determined eight repetition maximum) either at 7 am (fasting) or 5 pm. Sessions were performed at least 48 hours apart. Venous blood samples were collected immediately pre-, immediately post-, and 60-minutes post-exercise. Interstitial glucose was monitored overnight post-exercise by continuous glucose monitoring (CGM).
Results:
Data are presented as mean ± SD. Blood glucose rose during fasting morning exercise (9.5 ± 3.0 to 10.4 ± 3.0 mmol/L) while it declined with afternoon exercise (8.2 ± 2.5 to 7.4 ± 2.6 mmol/L; p=0.031 for time by treatment interaction). Sixty minutes post-exercise, blood glucose concentration was significantly higher after fasting morning exercise compared to afternoon exercise (10.9 ± 3.2 vs. 7.9 ± 2.9; p=0.019). CGM data indicated more glucose variability (2.7 ± 1.1 vs. 2.0 ± 0.7 mmol/L; p=0.019) and more frequent hyperglycemia (12 events vs. 5 events; p=0.025) after morning RE compared to afternoon RE. There were two hypoglycemic events after morning RE compared to four after afternoon RE (NS).
Conclusions:
Morning (fasting) RE is associated with distinctly different blood glucose responses and post-exercise profiles from afternoon RE.
... A study on 54 people with type 1 diabetes and the implementation of continuous moderate-intensity aerobic exercise by adding high-pressure intervals based on heart rate at three levels of 70, 80, and 90% of the maximum heart rate showed that adding high-pressure intervals to high-intensity exercise Moderate may increase the risk of hypoglycemia at higher intensities. However, another study showed that performing high-intensity interval training both in the morning and in the evening can be effective in controlling blood sugar in type 1 diabetics and reduce the frequency of hypoglycemic events after exercise [16]. ...
... On the other hand, people who did Trinate with high-pressure intervals (intervals) in the evening had less hyperglycemia than people who did these exercises in the morning (at 7 o'clock), and increased blood sugar peaks that were detected using a 24-hour glucose monitoring device. (CGM) recorded was lower than the morning exercise group and also the control group [16]. However, type 1 diabetics who underwent interval training with high-pressure intervals in the morning (7 o'clock) experienced fewer hypoglycemia events than the control group and the evening exercise group. ...
... It is interesting to note that according to the information obtained from the CGM device, the highest drop in blood sugar in type 1 diabetics who participated in the evening exercise occurred in the early morning of the next day. However, people who exercise in the morning, have experienced less hypoglycemia, but most of these incidents occurred in the middle of the night [16], which seems to have more risks for the individual [19]. ...
Exercise is recommended for the treatment and prevention of type 2 diabetes. Also, to control and reduce glucose fluctuations in people with type 1 diabetes. However, the most appropriate time and the most effective intensity of exercise is still unknown, and various studies provide different results and different recommendations, and none of the studies provide a comprehensive and practical result. We conducted our studies to examine the results and determine the effect of time and intensity of exercise on blood sugar control and glucose fluctuations during the day. Methods: search in PubMed and Google Scholar with keywords morning, evening, type 1 and 2 diabetes, exercise, interval, periodic, aerobic, and glucose and blood sugar fluctuations were performed. A total of 31 articles were reviewed and finally, 10 articles that were most related to each other or had complementary information were selected. Conclusion: HIIT exercises are useful for type 2 diabetes, but they are recommended for type 1 diabetes with less pressure. Morning exercise increases glucose and evening exercise is applicable for type 1 and 2 diabetes.
... Cave Die diabetische Ketoazidose ist eine potenziell lebensbedrohliche Stoffwechselentgleisung und kommt vermehrt bei Menschen mit Typ-1-Diabetes und Blutglukosewerten > 250-300 mg/dl (> 13, [9][10][11][12][13][14][15][16]7 ...
... Generell wird eher ein Anstieg beobachtet, wenn das Training morgens nüchtern durchgeführt wurde, nicht jedoch, wenn das Training zu einem anderen Zeitpunkt wenige Stunden nach dem Essen durchgeführt wurde [11]. Eine Studie mit 12 Probanden, welche morgens nüchtern und nachtmittags nicht nüchtern trainierten, stützt die Beobachtung eines deutlich unterschiedlichen Blutglukoseprofils abhängig vom Zeitpunkt des Trainings und der Nahrungsaufnahme [12]. Jedoch werden weitere Einflussfaktoren wie das Dawn-Phänomen (frühmorgendliche Hyperglykämie), Unterschiede von zirkulierendem Insulin und eine sich über den Tag verändernde Insulinsensitivität als Ursache diskutiert [12]. ...
... Eine Studie mit 12 Probanden, welche morgens nüchtern und nachtmittags nicht nüchtern trainierten, stützt die Beobachtung eines deutlich unterschiedlichen Blutglukoseprofils abhängig vom Zeitpunkt des Trainings und der Nahrungsaufnahme [12]. Jedoch werden weitere Einflussfaktoren wie das Dawn-Phänomen (frühmorgendliche Hyperglykämie), Unterschiede von zirkulierendem Insulin und eine sich über den Tag verändernde Insulinsensitivität als Ursache diskutiert [12]. ...
Sport verbessert die körperliche Fitness, beugt Herz-Kreislauf-Erkrankungen vor und steigert das psychische Wohlbefinden. Eine der größten Herausforderungen im Alltag von Menschen mit Typ-1-Diabetes ist es, den Glukosespiegel vor, während und nach dem Sport im physiologischen Bereich zu halten. In diesem Beitrag beschreiben wir, durch welche gezielten Maßnahmen Menschen mit Typ-1-Diabetes ihr Glukosemanagement bei Sport verbessern können.
Publication History
Article published online:
15 February 2024
© 2024. Thieme. All rights reserved.
Georg Thieme Verlag KG
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... Cave Die diabetische Ketoazidose ist eine potenziell lebensbedrohliche Stoffwechselentgleisung und kommt vermehrt bei Menschen mit Typ-1-Diabetes und Blutglukosewerten > 250-300 mg/dl (> 13, [9][10][11][12][13][14][15][16]7 ...
... Generell wird eher ein Anstieg beobachtet, wenn das Training morgens nüchtern durchgeführt wurde, nicht jedoch, wenn das Training zu einem anderen Zeitpunkt wenige Stunden nach dem Essen durchgeführt wurde [11]. Eine Studie mit 12 Probanden, welche morgens nüchtern und nachtmittags nicht nüchtern trainierten, stützt die Beobachtung eines deutlich unterschiedlichen Blutglukoseprofils abhängig vom Zeitpunkt des Trainings und der Nahrungsaufnahme [12]. Jedoch werden weitere Einflussfaktoren wie das Dawn-Phänomen (frühmorgendliche Hyperglykämie), Unterschiede von zirkulierendem Insulin und eine sich über den Tag verändernde Insulinsensitivität als Ursache diskutiert [12]. ...
... Eine Studie mit 12 Probanden, welche morgens nüchtern und nachtmittags nicht nüchtern trainierten, stützt die Beobachtung eines deutlich unterschiedlichen Blutglukoseprofils abhängig vom Zeitpunkt des Trainings und der Nahrungsaufnahme [12]. Jedoch werden weitere Einflussfaktoren wie das Dawn-Phänomen (frühmorgendliche Hyperglykämie), Unterschiede von zirkulierendem Insulin und eine sich über den Tag verändernde Insulinsensitivität als Ursache diskutiert [12]. ...
For many people with type 1 diabetes, sport is a central part of their lives. Sport improves physical fitness, prevents cardiovascular diseases and increases the psychological well-being of persons with type 1 diabetes. In addition, exercise increases insulin sensitivity. However, one of the biggest challenges in the daily life of individuals with type 1 diabetes is to maintain glucose levels in the physiological range before, during and after exercise. In addition, the fear of hypoglycemia discourages many people with type 1 diabetes from exercising. In this article, we show what targeted measures persons with type 1 diabetes can use to improve their glucose management during exercise. A better understanding of management options can encourage people with type 1 diabetes to increase their physical activity.
... 17,18 Time-dependent exercise has different outcomes, 19 as shown by the greater increases in endurance capacity gained by evening exercise compared to morning exercise, 20 and the better glycemic control and weight control in obese and overweight individuals due to evening exercise. [21][22][23][24][25] (Table 1) Moderate to vigorous exercise is more effective in the evening where it reduced insulin resistance by 25%. 26 Exercise in the afternoon by patients at risk of diabetes experienced superior benefits on peripheral insulin sensitivity, fasting plasma glucose levels, exercise performance, increased fatty acid oxidation, and fat mass loss. ...
... 27,28 While morning exercise leads to an increase in blood glucose concentration. 21,25 In 1981, Schmidt proposed the term "dawn phenomenon" to describe the abrupt elevation of blood glucose levels that spontaneously occur in the morning. 29 The rise in blood glucose following morning exercise has been J o u r n a l P r e -p r o o f linked to the extension of this phenomenon, likely caused by elevated cortisol levels. ...
... Savikj et al. 21 Moholdt et al. 24 Toghi-Eshghi et al. 25 Syeda et al. 22 Kim et al. 28 Effect of morning and evening exercise on blood glucose levels ...
Exercise has well-characterized therapeutic benefits in the management of type 2 diabetes mellitus (T2DM). Most of the beneficial effects of exercise arise from the impact of nuclear factor erythroid 2 related factor-2 (Nrf2) activation of glucose metabolism. Nrf2 is an essential controller of cellular anti-oxidative capacity and circadian rhythms. The circadian rhythm of Nrf2 is influenced by circadian genes on its expression, where the timing of exercise effects the activation of Nrf2 and the rhythmicity of Nrf2 and signaling, such that the timing of exercise has differential physiological effects. Exercise in the evening has beneficial effects on diabetes management, such as lowering of blood glucose and weight. The mechanisms responsible for these effects have not yet been associated with the influence of exercise on the circadian rhythm of Nrf2 activity. A better understanding of exercise-induced Nrf2 activation on Nrf2 rhythm and signaling can improve our appreciation of the distinct effects of morning and evening exercise. This review hypothesizes that activation of Nrf2 by exercise in the morning, when Nrf2 level is already at high levels, leads to hyperactivation and decrease in Nrf2 signaling, while activation of Nrf2 in the evening, when Nrf2 levels are at nadir levels, improves Nrf2 signaling and lowers blood glucose levels and increases fatty acid oxidation. Exploring the effects of Nrf2 activators on rhythmic signaling could also provide valuable insights into the optimal timing of their application, while also holding promise for timed treatment of type 2 diabetes.
... However, current guidelines do not thoroughly discuss the impact of prandial state (i.e. the time elapsed since participants' last meal pre-exercise), as recently addressed in two letters in Diabetologia [7,8], nor do they address different modalities of exercise. Glycaemic responses to exercise vary substantially between fasted or fed conditions [9][10][11]. Exercise performed fasted or in a post-absorptive state does not coincide with maximal levels of insulin on board (IOB; and hence, peak prandial insulin action), resulting in easier insulin management and lower hypoglycaemia risk [9,11,12]. In contrast, postprandial exercise (i.e. ...
... Glycaemic responses to exercise vary substantially between fasted or fed conditions [9][10][11]. Exercise performed fasted or in a post-absorptive state does not coincide with maximal levels of insulin on board (IOB; and hence, peak prandial insulin action), resulting in easier insulin management and lower hypoglycaemia risk [9,11,12]. In contrast, postprandial exercise (i.e. ...
... This suggests that in people with type 1 diabetes, in a postprandial setting, non-insulin mediated glucose uptake by muscle is a very important mechanism that has a large impact on blood glucose decreases during exercise, and is perhaps more important than the amount of circulating prandial insulin per se. The glycaemic decline during exercise in the prandial state is, thus, the result of three factors: (1) insulin-independent GLUT-4 translocation; together with (2) the presence of (a certain amount of) rapid-acting insulin; and also (3) low(er) levels of growth hormone, cortisol, glucagon and other counter-regulatory hormones (that would avoid glycaemic declines, or even increase blood glucose, as generally observed during fasted exercise in people with type 1 diabetes) [9,11]. ...
People with type 1 diabetes experience challenges in managing blood glucose around exercise. Previous studies have examined glycaemic responses to different exercise modalities but paid little attention to participants’ prandial state, although this is an important consideration and will enhance our understanding of the effects of exercise in order to improve blood glucose management around activity. This review summarises available data on the glycaemic effects of postprandial exercise (i.e. exercise within 2 h after a meal) in people with type 1 diabetes. Using a search strategy on electronic databases, literature was screened until November 2022 to identify clinical trials evaluating acute (during exercise), subacute (≤2 h after exercise) and late (>2 h to ≤24 h after exercise) effects of postprandial exercise in adults with type 1 diabetes. Studies were systematically organised and assessed by exercise modality: (1) walking exercise (WALK); (2) continuous exercise of moderate intensity (CONT MOD); (3) continuous exercise of high intensity (CONT HIGH); and (4) interval training (intermittent high-intensity exercise [IHE] or high-intensity interval training [HIIT]). Primary outcomes were blood glucose change and hypoglycaemia occurrence during and after exercise. All study details and results per outcome were listed in an evidence table. Twenty eligible articles were included: two included WALK sessions, eight included CONT MOD, seven included CONT HIGH, three included IHE and two included HIIT. All exercise modalities caused consistent acute glycaemic declines, with the largest effect size for CONT HIGH and the smallest for HIIT, depending on the duration and intensity of the exercise bout. Pre-exercise mealtime insulin reductions created higher starting blood glucose levels, thereby protecting against hypoglycaemia, in spite of similar declines in blood glucose during activity between the different insulin reduction strategies. Nocturnal hypoglycaemia occurred after higher intensity postprandial exercise, a risk that could be diminished by a post-exercise snack with concomitant bolus insulin reduction. Research on the optimal timing of postprandial exercise is inconclusive. In summary, individuals with type 1 diabetes exercising postprandially should substantially reduce insulin with the pre-exercise meal to avoid exercise-induced hypoglycaemia, with the magnitude of the reduction depending on the exercise duration and intensity. Importantly, pre-exercise blood glucose and timing of exercise should be considered to avoid hyperglycaemia around exercise. To protect against late-onset hypoglycaemia, a post-exercise meal with insulin adjustments might be advisable, especially for exercise in the evening or with a high-intensity component.
Graphical abstract
... A handful of small studies, using repeated measures study designs, have compared fasted vs fed exercise using a single group of participants with type 1 diabetes within each study. Where anaerobic exercise is concerned, two separate studies (both n=12) showed clear blood glucose decreases with afternoon resistance [27] and HIIE [28] (performed~4-5 h after a meal), while the same protocols performed by the same participants after an overnight fast resulted in an increase or no change in blood glucose, respectively. Even aerobic exercise, thought to consistently decrease blood glucose levels [3,4], can increase blood glucose when performed under these conditions [29,30]. ...
... As triglycerides are metabolised, the resulting glycerol could act as a gluconeogenic precursor, thereby increasing blood glucose. The resulting increase in circulating NEFA from lipolysis (which are higher after fasted exercise) [32] could also temporarily increase insulin resistance [33], which would account for rising blood glucose levels during exercise, and persistent hyperglycaemia [16,27] after exercise, when performed after an overnight fast. ...
... As can be seen in Fig. 2, changes in glucose during fasted resistance exercise (Fig. 2a [methods described elsewhere [27]]) and fasted HIIE (Fig. 2b [methods described elsewhere [28]]), show that most participants experience rising blood glucose levels during fasted anaerobic exercise (9 out of 12 and 10 out of 12, respectively). Riddell et al [16] also noted this response among 16 participants with type 1 diabetes (four female; aged 34. ...
Recent guidelines suggest that adding anaerobic (high intensity or resistance) activity to an exercise session can prevent blood glucose declines that occur during aerobic exercise in individuals with type 1 diabetes. This theory evolved from earlier study data showing that sustained, anaerobic activity (high intensity cycling) increases blood glucose levels in these participants. However, studies involving protocols where anaerobic (high intensity interval) and aerobic exercise are combined have extremely variable glycaemic outcomes, as do resistance exercise studies. Scrutinising earlier studies will reveal that, in addition to high intensity activity (intervals or weight lifting), these protocols had another common feature: participants were performing exercise after an overnight fast. Based on these findings, and data from recent exercise studies, it can be argued that participant prandial state may be a more dominant factor than exercise intensity where glycaemic changes in individuals with type 1 diabetes are concerned. As such, a reassessment of study outcomes and an update to exercise recommendations for those with type 1 diabetes may be warranted.
Graphical abstract
... Five studies verified the effect of resistance training programs on HbA1c (16,17,18,19). The data of 115 participants were analyzed. ...
... No significant publication bias was detected in the asymmetry of the funnel graph or in the Egger test (p = 0.308). According to the sensitivity analysis for the resistance training group (Figure 3), heterogeneity reduced significantly between the groups to 20% (p = 0.287), after removing one study (18). Due to the reduced number of studies for the other analyses, it was not possible to conduct a sensitivity analysis. ...
... There was inconsistency in the study by Toghi-Eshghi and Yardley (18), while all the others identified a reduction in the effect size analysis, these authors reported an increase. One hypothesis for this occurrence is that, in this case, the patients performed the training protocol at two different moments: fasting at 7am and fed during the afternoon. ...
Resistance training has shown the potential to contribute to better glycemic control in people with Type 1 Diabetes (T1D), however, there are contradictory results in this regard and a need to clarify the effects of isolated resistance training on glycemic control in T1D. The aim was to verify the effects of resistance training on the glycemic control of people with T1D. Original articles were selected, randomized and non-randomized clinical trials that aimed to verify chronic responses, through the concentrations of glycated hemoglobin (HbA1c), to a structured program of resistance exercise in the glycemia of patients with T1D. The following databases were searched; MEDLINE, PubMed, Web of Science, Scopus, ScienceDirect, LILACS, and SciELO. Five studies were included in the review. A reduction in HbA1c was observed (SMD = -0.568 ± 0.165 [95% CI = -0.891 to -0.246]; p = 0.001; I2 = 82%) in patients undergoing resistance training, when compared to the control group (SMD = 1.006 ± 0.181 [95% CI = 0.653 to 1.360]; p <0.001). Two studies, with children and adolescents and longer interventions, demonstrated a significant reduction in HbA1c, increased strength, and an improved lipid profile. Resistance training was efficient for assisting in glycemic control in people with T1D and should be incorporated in treatment plans.
... Using a repeated measures design, Toghi-Eshghi and Yardley (2019) compared the response of a group of participants with T1D to an identical resistance exercise protocol performed once in the fed state (around 5 p.m.) and once in the fasted state (around 7 a.m.) to replicate the scenarios from the previous studies. 10 They found that intra-individual blood glucose was more likely to increase during fasted morning resistance exercise, while it decreased when the same protocol was performed later in the day. 10 As such, performing resistance exercise while fasted can be advised for individuals with T1D for whom the fear of hypoglycemia is a major barrier to being active. ...
... 10 They found that intra-individual blood glucose was more likely to increase during fasted morning resistance exercise, while it decreased when the same protocol was performed later in the day. 10 As such, performing resistance exercise while fasted can be advised for individuals with T1D for whom the fear of hypoglycemia is a major barrier to being active. The physiology behind these blood glucose responses to fasted exercise are described in detail elsewhere. ...
Exercise and physical activity are associated with many benefits for individuals with type 1 diabetes (T1D), including increased longevity and a decrease in the incidence/severity of diabetes-related complications. Unfortunately, these activities (and aerobic exercise in particular) also increase the risk of hypoglycemia and glycemic variability, both of which act as barriers to being more active in this population. Resistance exercise is an often-overlooked activity, as historically it has been seen in training reserved for elite athletes. For individuals with T1D, it is associated with a multitude of benefits including a reduced risk of hypoglycemia during activity. With improved insulin formulations and rapid increases in technology to manage T1D, people with this condition are living longer, healthier lives. This article describes the many reasons why resistance exercise should be a part of this longevity.
... Several studies demonstrated that performing aerobic exercise in the afternoon or evening increases the risk of hypoglycemic episodes, especially nocturnal ones [26,[28][29][30]. In our study, time to hypoglycemia onset was prolonged after the resistance as opposed to aerobic training (13 vs. 8 h), explaining the lack of nocturnal hypoglycemia after the resistance compared to aerobic exercise (4 vs. 0). ...
... Our results are further substantiated by the recent meta-analysis focusing on the delayed effects of different exercise modalities. Additionally, Valli et al. demonstrated that there is a reduced risk of hypoglycemia if exercise is performed in the morning rather than in the afternoon with a 50% rapid-acting insulin reduction, but no definite benefits of resistance exercise were determined [30,31]. Based on the current recommendations, exercise should ideally be performed in the morning or at noon. ...
Citation: Ivandic, M.; Cigrovski Berkovic, M.; Ormanac, K.; Sabo, D.; Omanovic Kolaric, T.; Kuna, L.; Mihaljevic, V.; Canecki Varzic, S.; Smolic, M.; Bilic-Curcic, I. Abstract: (1) Background: The increased risk of developing hypoglycemia and worsening of glycemic stability during exercise is a major cause of concern for patients with type 1 diabetes mellitus (T1DM). (2) Aim: This pilot study aimed to assess glycemic stability and hypoglycemic episodes during and after aerobic versus resistance exercises using a flash glucose monitoring system in patients with T1DM. (3) Participants and Methods: We conducted a randomized crossover prospective study including 14 adult patients with T1DM. Patients were randomized according to the type of exercise (aerobic vs. resistance) with a recovery period of three days between a change of groups. Glucose stability and hypoglycemic episodes were evaluated during and 24 h after the exercise. Growth hormone (GH), cortisol, and lactate levels were determined at rest, 0, 30, and 60 min post-exercise period. (4) Results: The median age of patients was 53 years, with a median HbA1c of 7.1% and a duration of diabetes of 30 years. During both training sessions, there was a drop in glucose levels immediately after the exercise (0), followed by an increase at 30 and 60 , although the difference was not statistically significant. However, glucose levels significantly decreased from 60 to 24 h in the post-exercise period (p = 0.001) for both types of exercise. Glycemic stability was comparable prior to and after exercise for both training sessions. No differences in the number of hypoglycemic episodes, duration of hypoglycemia, and average glucose level in 24 h post-exercise period were observed between groups. Time to hypoglycemia onset was prolonged after the resistance as opposed to aerobic training (13 vs. 8 h, p = NS). There were no nocturnal hypoglycemic episodes (between 0 and 6 a.m.) after the resistance compared to aerobic exercise (4 vs. 0, p = NS). GH and cortisol responses were similar between the two sessions, while lactate levels were significantly more increased after resistance training. (5) Conclusion: Both exercise regimes induced similar blood glucose responses during and immediately following acute exercise.
... Participants were told to use the provided guidelines regardless of the type of exercise they were performing. Since the design and implementation of this study, it has been demonstrated that declines in blood glucose with resistance exercise (using a similar exercise protocol to that of READI) are smaller than those seen with aerobic exercise (32), and that blood glucose levels may actually increase if resistance exercise is performed in a fasted state (33). A recent consensus statement (34) on exercise for individuals with type 1 diabetes recommends a lower starting blood glucose level of 5.0 to 7.0 mmol/L (90-126 mg/dL) for anaerobic activities (such as resistance exercise), compared to 7.0 to 10.0 mmol/L (126-180 mg/dL) for aerobic activities. ...
... Second, we did not have enough study participants to determine if there are sex-related differences in the glycemic responses to resistance exercise. Third, the time of day for resistance exercise was not standardized and emerging data suggest that there may be time-of-day effects on glycemic response to exercise (33,36,37). Fourth, we were unable to mask participants to their group assignment, as with any exercise intervention, although study outcome measures were blinded. ...
OBJECTIVE
To evaluate the incremental impact of resistance training on HbA1c, fitness, body composition and cardiometabolic risk factors in aerobically-active people with type 1 diabetes.
RESEARCH DESIGN AND METHODS
The Resistance Exercise in Already-active Diabetic Individuals (READI) trial (NCT00410436) was a four-centre randomized parallel-group trial. After a 5-week run-in period with diabetes management optimization, 131 aerobically-active individuals with type 1 diabetes were randomized to resistance exercise (n = 71, intervention - INT) or control (n = 60, CON) for 22 additional weeks. Both groups maintained their aerobic activities and were provided dietary counselling throughout. Exercise training was three times per week at community-based facilities. The primary outcome was HbA1c, and secondary outcomes included fitness (peak oxygen consumption, muscle strength), body composition (anthropometrics, dual-energy X-ray absorptiometry, computed tomography) and cardiometabolic risk markers (lipids, apolipoproteins). Assessors were blinded to group allocation.
RESULTS
There were no significant differences in HbA1c change between INT and CON. Declines in HbA1c [INT: 7.75 ± 0.10% (61.2 ± 1.1 mmol/mol) to 7.55 ± 0.10% (59 ± 1.1 mmol/mol); CON: 7.70 ± 0.11% (60.7 ± 1.2 mmol/mol) to 7.57 ± 0.11% (59.6 ± 1.3 mmol/mol); intergroup difference in change -0.07 [95% CI -0.31, 0.18]. Waist circumference decreased more in INT than CON after six months (p = 0.02). Muscular strength increased more in INT than in CON (p < 0.001). There were no intergroup differences in hypoglycemia or any other variables.
CONCLUSIONS
Adding resistance training did not impact glycemia, but it increased strength and reduced waist circumference, in aerobically active individuals with type 1 diabetes.
... Interestingly, a decrease in blood glucose concentration can be observed when a session is performed for a longer period of time (>3 sets) [65]. In a recent study, Eshghi and Yardley showed that a morning resistance exercise session led to an increase in blood glucose concentration while an afternoon session led to a decrease [67]. Although the findings are of interest, the questions arise if the participant`s morning blood glucose could at least partially be due to the Dawn Phenomenon [68] and if the decrease in the blood glucose concentration can be attributed to a peak in the basal insulin action [69]. ...
... To increase muscle mass hypertrophy via resistance training, various training methods, intensities and durations have been investigated in healthy individuals [105][106][107]. In type 1 diabetes, resistance exercise was shown to have smaller impact on the blood glucose decrease than aerobic exercise and may even offer a protective effect on blood glucose if performed prior to exercise [65][66][67]108] It was shown in healthy individuals that the speed of movement can have an impact on the hypertrophic response, in particular with regards to the lengthening of the muscle/eccentric movement, which is suspected to be due to the enhanced hypoxia, ischemia and metabolic response which augments the hypertrophic response [109,110]. ...
ype 1 diabetes is characterized by an autoimmune β-cell destruction resulting in endogenous insulin deficiency, potentially leading to micro- and macrovascular complications. Besides an exogenous insulin therapy and continuous glucose monitoring, physical exercise is recommended in adults with type 1 diabetes to improve overall health. The close relationship between physical exercise, inflammation, muscle contraction, and macronutrient intake has never been discussed in detail about type 1 diabetes. The aim of this narrative review was to detail the role of physical exercise in improving clinical outcomes, physiological responses to exercise and different nutrition and therapy strategies around exercise.
Physical exercise has several positive effects on glucose uptake and systemic inflammation in adults with type 1 diabetes. A new approach via personalized therapy adaptations must be applied to target beneficial effects on complications as well as on body weight management. In combination with pre-defined macronutrient intake around exercise, adults with type 1 diabetes can expect similar physiological responses to physical exercise, as seen in their healthy counterparts.
This review highlights interesting findings from recent studies related to exercise and type 1 diabetes. However, there is limited research available accompanied by a proper number of participants in the cohort of type 1 diabetes. Especially for this group of patients, an increased understanding of the impact of physical exercise can improve its effectiveness as an adjuvant therapy to move (forward).
... 67 As outlined above, several exercise guidelines also recommend the inclusion of either resistance exercise, or high-intensity intervals, with aerobic exercise, as the combination seems to blunt the declines in blood glucose generally observed during aerobic exercise. [37][38][39] In addition, recent studies not included in current guidelines have shown that fasting resistance exercise 68 and high-intensity intermittent exercise, 69 may result in increases in blood glucose, where the same activity performed in the fed state later in the day could result in a decline in blood glucose levels. The same has also been found of aerobic exercise. ...
... 70 This phenomenon has been attributed to both the lower amount of insulin in circulation from a lack of meal-related bolus insulin, as well as higher concentrations of growth hormone and cortisol, which may promote lipids as a fuel source and thereby spare blood glucose during exercise. [68][69][70] Taken together, exercising before breakfast, may be advisable for active individuals with type 1 diabetes who are struggling with hypoglycemia, or are held back in their activities by the fear of hypoglycemia. ...
Jane E Yardley1–4 1Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Canada; 2Alberta Diabetes Institute, Edmonton, Canada; 3Augustana Faculty, University of Alberta, Camrose, Canada; 4Women’s and Children’s Research Institute, Edmonton, CanadaCorrespondence: Jane E YardleyAugustana Faculty, University of Alberta, 4901 – 46th Avenue, Camrose, AB T4V 2R3, CanadaTel +1 780 679 1688Fax +1 780 679 1590Email jane.yardley@ualberta.caAbstract: Fear of hypoglycemia is a common barrier to exercise and physical activity for individuals with type 1 diabetes. While some of the earliest studies in this area involved only one or two participants, the link between exercise, exogenous insulin, and hypoglycemia was already clear, with the only suggested management strategies being to decrease insulin dosage and/or consume carbohydrates before and after exercise. Over the past 50 years, a great deal of knowledge has been developed around the impact of different types and intensities of exercise on blood glucose levels in this population. Recent decades have also seen the development of technologies such as continuous glucose monitors, faster-acting insulins and commercially available insulin pumps to allow for the real-time observation of interstitial glucose levels, and more precise adjustments to insulin dosage before, during and after activity. As such, there are now evidence-based exercise and physical activity guidelines for individuals with type 1 diabetes. While the risk of hypoglycemia has not been completely eliminated, therapy recommendations have evolved considerably. This review discusses the evolution of the knowledge and the technology related to type 1 diabetes and exercise that have allowed this evolution to take place.Keywords: exercise, physical activity, blood glucose, insulin, carbohydrate, continuous glucose monitoring
... 8 The increase in hepatic glucose production may overcompensate for the increased muscle glucose utilization rate during heavy resistance exercise and may cause a rise in blood glucose level, particularly if done fasted. 9 Conversely, during aerobic exercise, the sustained high demand for glucose by peripheral tissues can surpass counterregulatory mechanisms, resulting in a decrease in blood glucose levels. 7 Prolonged aerobic exercise oftentimes results in large drops in glucose levels and poses increased risk for hypoglycemia. ...
Background
Managing glucose levels during exercise is challenging for individuals with type 1 diabetes (T1D) since multiple factors including activity type, duration, intensity and other factors must be considered. Current decision support tools lack personalized recommendations and fail to distinguish between aerobic and resistance exercise. We propose an exercise-aware decision support system (exDSS) that uses digital twins to deliver personalized recommendations to help people with T1D maintain safe glucose levels (70-180 mg/dL) and avoid low glucose (<70 mg/dL) during and after exercise.
Methods
We evaluated exDSS using various exercise and meal scenarios recorded from a large, free-living study of aerobic and resistance exercise. The model inputs were heart rate, insulin, and meal data. Glucose responses were simulated during and after 30-minute exercise sessions (676 aerobic, 631 resistance) from 247 participants. Glucose outcomes were compared when participants followed exDSS recommendations, clinical guidelines, or did not modify behavior (no intervention).
Results
exDSS significantly improved mean time in range for aerobic (80.2% to 92.3%, P < .0001) and resistance (72.3% to 87.3%, P < .0001) exercises compared with no intervention, and versus clinical guidelines (aerobic: 82.2%, P < .0001; resistance: 80.3%, P < .0001). exDSS reduced time spent in low glucose for both exercise types compared with no intervention (aerobic: 15.1% to 5.1%, P < .0001; resistance: 18.2% to 6.6%, P < .0001) and was comparable with following clinical guidelines (aerobic: 4.5%, resistance: 8.1%, P = N.S.).
Conclusions
The exDSS tool significantly improved glucose outcomes during and after exercise versus following clinical guidelines and no intervention providing motivation for clinical evaluation of the exDSS system.
... The experimental conditions adopted for our study (warm or cool water as well as basal insulinemia) mimic those experienced by summer beachgoers before breakfast, a time of day when the risk of both hypoglycemia and exercise-mediated hypoglycemia are at their lowest in people with T1DM [38][39][40]. Our experimental conditions were also chosen to be relevant to the many individuals with T1DM who attend beaches with cool or warm water temperature. ...
Context
It is unclear whether immersion in cool water, typical of many beaches, increases the concentration of blood glucose in individuals with type 1 diabetes mellitus (T1DM).
Objective
To test the hypothesis in individuals with T1DM that immersion neck-deep in cool water (COOL) causes an increase in blood glucose concentration, but not exposure to thermoneutral water (THERMO) or thermoneutral air.
Methods
Eight overnight-fasted participants with T1DM were exposed for 60 minutes on separate days to 3 experimental conditions: cool water (COOL, 23 °C); thermoneutral water (THERMO, 33.5 °C); or thermoneutral air (24 °C). They then recovered for 60 minutes on land at 24 °C. At time intervals, we measured: blood glucose and plasma insulin concentration, rate of carbohydrate and fat oxidation, skin and core temperature, subcutaneous blood flow, and shivering via electromyography.
Results
There was no change in blood glucose concentration during the 3 experimental conditions (P > .05). During recovery after COOL, blood glucose increased (P < .05) but did not change in the other 2 conditions. The rate of carbohydrate oxidation during and early after COOL was higher than in the other 2 conditions (P < .05), and COOL led to a decrease in subcutaneous blood flow and the concentration of plasma insulin (P < .05).
Conclusion
Cool or thermoneutral neck-deep immersion in water does not cause a change in the concentration of blood glucose in people with T1DM, but on-land recovery from COOL causes an increase in blood glucose that may be due, at least in part, to the accompanying decrease in plasma insulin.
... Nevertheless, it is important to acknowledge that several studies have indicated potential advantages of afternoon exercise in individuals with metabolic challenges. For example, in individuals with type 1 diabetes, post-exercise blood glucose levels were notably lower following afternoon resistance exercise (RE) compared to fasting morning RE (Toghi-Eshghi and Yardley, 2019). In men with type 2 diabetes, a 2-week regimen of afternoon high-intensity interval training (HIIT) not only led to more substantial improvements in blood glucose levels than morning HIIT but also resulted in an increase in thyroid-stimulating hormone (TSH) levels, accompanied by enhancements in mitochondrial content and skeletal muscle lipid profiles (Savikj et al., 2018;Savikj et al., 2022). ...
The biological clock system is an intrinsic timekeeping device that integrates internal physiology and external cues. Maintaining a healthy biological clock system is crucial for life. Disruptions to the body’s internal clock can lead to disturbances in the sleep-wake cycle and abnormalities in hormone regulation, blood pressure, heart rate, and other vital processes. Long-term disturbances have been linked to the development of various common major diseases, including cardiovascular diseases, metabolic disorders, tumors, neuropsychiatric conditions, and so on. External factors, such as the diurnal rhythm of light, have a significant impact on the body’s internal clock. Additionally, as an important non-photic zeitgeber, exercise can regulate the body’s internal rhythms to a certain extent, making it possible to become a non-drug intervention for preventing and treating circadian rhythm disorders. This comprehensive review encompasses behavioral, physiological, and molecular perspectives to provide a deeper understanding of how exercise influences circadian rhythms and its association with related diseases.
... In general, the key contributors to glycemic responses to PA appear to include the type of PA (aerobic vs. resistance or mixed activity), prandial status (fed vs. fasted activity), circulating insulin level, blood glucose level at the start of the activity, glucose trends preceding the activity, composition of the most recent meal or snack, as well as the intensity and duration of the activity [41,42]. Recent evidence suggests that the time of day at which exercise is performed and prandial status are important determinants for the glucose response to PA [43][44][45][46][47][48][49]. Specifically among those with T1D, exercise performed later in the day has been shown to promote a greater drop in glucose levels compared to morning exercise, with afternoon and lateday exercise also heightening the risk of nocturnal hypoglycemia [46,50]. ...
The prevalence of overweight and obesity in young people with type 1 diabetes (T1D) now parallels that of the general population. Excess adiposity increases the risk of cardiovascular disease, which is already elevated up to 10-fold in T1D, underscoring a compelling need to address weight management as part of routine T1D care. Sustainable weight management requires both diet and physical activity (PA). Diet and PA approaches must be optimized towards the underlying metabolic and behavioral challenges unique to T1D to support glycemic control throughout the day. Diet strategies for people with T1D need to take into consideration glycemic management, metabolic status, clinical goals, personal preferences, and sociocultural considerations. A major barrier to weight management in this high-risk population is the challenge of integrating regular PA with day-to-day management of T1D. Specifically, exercise poses a substantial challenge due to the increased risk of hypoglycemia and/or hyperglycemia. Indeed, about two-thirds of individuals with T1D do not engage in the recommended amount of PA. Hypoglycemia presents a serious health risk, yet prevention and treatment often necessitates the consumption of additional calories, which may prohibit weight loss over time. Exercising safely is a concern and challenge with weight management and maintaining cardiometabolic health for individuals living with T1D and many healthcare professionals. Thus, a tremendous opportunity exists to improve exercise participation and cardiometabolic outcomes in this population. This article will review dietary strategies, the role of combined PA and diet for weight management, current resources for PA and glucose management, barriers to PA adherence in adults with T1D, as well as findings and lessons learned from the Advancing Care for Type 1 Diabetes and Obesity Network (ACT1ON).
... Finally, one might be cautious about applying these findings when exercise is performed at a different time of the day. Compared with afternoon exercise, morning exercise can be associated with higher glycemia 39 and a lower risk of postexercise hypoglycemic events in PWT1D. 40 Thus, it might be necessary for patients to adjust their approach (e.g., greater bolus reduction, additional pre-exercise carbohydrates) when exercising later in the day. ...
Aims:
To assess the safety and efficacy of two exercise sessions performed 60- and 120-minutes post-meal with a combination of meal bolus reduction and increased glucose target to the automated insulin delivery (AID) system.
Methods:
A randomized crossover trial in 13 adult participants (6 females) living with type 1 diabetes using AID (A1c = 7.9 ± 0.6%, Age = 53.5 ± 15.5 years, T1D duration = 29.0 ± 16.0 years) was conducted. Just before breakfast, at the time of meal bolus, the AID glucose target was increased from 6 to 9 mmol/L, and a meal bolus reduction of 33% was applied. Two 60-minute exercise sessions (60% of VO2 peak) were undertaken either 60 minutes (60EX) or 120 minutes (120EX) after a standardized breakfast, followed by a 90-minute recovery period.
Results:
The mean reduction in plasma glucose levels from pre-breakfast to post-exercise (-0.8 ± 2.4 mmol/L vs. +0.3 ± 2.3 mmol/L, p = 0.082) were similar between 60EX and 120EX. From pre-breakfast to post-exercise, plasma glucose times in range (3.9-10.0 mmol/L; 63.4 ± 43.1% 60EX vs. 51.9 ± 29.7% 120EX, p = 0.219) and time above range (>10.0 mmol/L; 36.3 ± 43.3% 60EX vs. 48.1 ± 29.7% 120EX, p = 0.211) did not differ between interventions. 60EX attenuated the glucose rise between pre-meal to pre-exercise (+1.8 ± 2.1 mmol/L 60EX vs. +3.9 ± 2.1 mmol/L 120EX, p = 0.001). No hypoglycemic events (<3.9 mmol/L) occurred during the study.
Conclusion:
Pre-meal announcement combining meal bolus reduction and increased glucose target was effective and safe during 60 minutes of moderate-intensity aerobic exercise, whether exercise onset was 60 or 120 minutes following a meal.
... The metabolic response to exercise at this time point is unlikely to represent exercise at other (early) time points of the day. Indeed, it has been shown that prior early morning exercise leads to a different blood glucose response to exercise than afternoon exercise [62]. ...
The purpose of this study was to examine sex-specific differences in the blood glucose (BG) response to recurrent aerobic exercise in type 1 diabetes rats. Specifically, we examined the role of peak estrogen (E2) concentrations during proestrus on BG response to prolonged repetitive aerobic exercise. To do so, nineteen Sprague-Dawley rats were assigned to four exercised groups: control female (CXF; n = 5), control male (CXM; n = 5), diabetic female (DXF, n = 5) and diabetic male (DXM, n = 4). Diabetes was induced in DX groups via subcutaneous multiple injections of low dose streptozotocin (20mg/day for 7 days). After four days of exercise, muscle and liver glycogen content, liver gluconeogenic enzyme content, muscle Beta oxidation activity and BG responses to exercise were compared. The final bout of exercise took place during proestrus when E2 concentrations were at their highest in the female rats. During days 1–3 DXM had significantly lower BG concentrations during exercise than DXF. While both T1DM and non-T1DM females demonstrated higher hepatic G6Pase expression and muscle beta oxidation activity levels on day 4 exercise, no differences in BG response between the male and female T1DM rats were evident. Further, no differences in liver and muscle glycogen content following day 4 of exercise were seen between the sexes. These results would suggest that heightened E2 levels during proestrus may not be an important factor governing glucose counter regulatory response to exercise in female T1DM rats. Rather, the pre-exercise blood glucose levels are likely to be a large determinant of the blood glucose response to exercise in both male and female rats.
... Notably, the studies by Turner et al. [16], Farinha et al. [9] and our group [17] used very similar resistance exercise protocols (with three sets of eight repetitions), both in terms of the exercises used and the intensity of the exercises [17]. Similar to HIIE, there is also a recent, small, crossover study [18] showing distinct patterns of response to a standardised resistance exercise protocol to compare morning (fasting) vs afternoon (postprandial) exercise: plasma glucose declined from 8.2 ± 2.5 mmol/l to 7.4 ± 2.6 mmol/l during afternoon, postprandial exercise, compared with an increase in plasma glucose from 9.5 ± 3.0 mmol/l to 10.4 ± 3.0 mmol/l (p = 0.031, time × treatment interaction) in the same participants during morning (fasted) exercise. ...
... increased risk of hypoglycaemia (Table 2) [38](D), [39](D). If sensor glucose is expected to increase, as often seen in people performing fasted high-intensity interval training [55,56], resistance training [49,65,66] and, also, in training above the anaerobic threshold [67], then an insulin correction can be administered at the onset of, as well as during exercise (50% of typical correction factor) [68](D), [69](D). ...
Physical exercise is an important component in the management of type 1 diabetes
across the lifespan. Yet, acute exercise increases the risk of dysglycaemia, and the
direction of glycaemic excursions depends, to some extent, on the intensity and dura-
tion of the type of exercise. Understandably, fear of hypoglycaemia is one of the stron-
gest barriers to incorporating exercise into daily life. Risk of hypoglycaemia during and
after exercise can be lowered when insulin-dose adjustments are made and/or addi-
tional carbohydrates are consumed. Glycaemic management during exercise has been
made easier with continuous glucose monitoring (CGM) and intermittently scanned
continuous glucose monitoring (isCGM) systems; however, because of the complexity
of CGM and isCGM systems, both individuals with type 1 diabetes and their healthcare
professionals may struggle with the interpretation of given information to maximise the
technological potential for effective use around exercise (ie, before, during and after).
This position statement highlights the recent advancements in CGM and isCGM tech-
nology, with a focus on the evidence base for their efficacy to sense glucose around
exercise and adaptations in the use of these emerging tools, and updates the guidance
for exercise in adults, children and adolescents with type 1 diabetes
... During exercise Independent of the type of exercise, the target sensor glucose ranges should be between 5.0 mmol/l and 10.0 mmol/l (90 mg/dl and180 mg/dl) and, ideally, between 7.0 mmol/l and 10.0 mmol/l (126 mg/dl and 180 mg/dl) for prolonged aerobic exercise for the majority of adults with type 1 diabetes, and slightly higher for those with an increased risk of hypoglycaemia (Table 2) [38] (D), [39] (D). If sensor glucose is expected to increase, as often seen in people performing fasted high-intensity interval training [55,56], resistance training [49,65,66] and, also, in training above the anaerobic threshold [67], then an insulin correction can be administered at the onset of, as well as during exercise (50% of typical correction factor) [68] (D), [69] (D). ...
Physical exercise is an important component in the management of type 1 diabetes across the lifespan. Yet, acute exercise increases the risk of dysglycaemia, and the direction of glycaemic excursions depends, to some extent, on the intensity and duration of the type of exercise. Understandably, fear of hypoglycaemia is one of the strongest barriers to incorporating exercise into daily life. Risk of hypoglycaemia during and after exercise can be lowered when insulin-dose adjustments are made and/or additional carbohydrates are consumed. Glycaemic management during exercise has been made easier with continuous glucose monitoring (CGM) and intermittently scanned continuous glucose monitoring (isCGM) systems; however, because of the complexity of CGM and isCGM systems, both individuals with type 1 diabetes and their healthcare professionals may struggle with the interpretation of given information to maximise the technological potential for effective use around exercise (i.e. before, during and after). This position statement highlights the recent advancements in CGM and isCGM technology, with a focus on the evidence base for their efficacy to sense glucose around exercise and adaptations in the use of these emerging tools, and updates the guidance for exercise in adults, children and adolescents with type 1 diabetes.
Graphical abstract
... During exercise Independent of the type of exercise, the target sensor glucose ranges should be between 5.0 mmol/l and 10.0 mmol/l (90 mg/dl and180 mg/dl) and, ideally, between 7.0 mmol/l and 10.0 mmol/l (126 mg/dl and 180 mg/dl) for prolonged aerobic exercise for the majority of adults with type 1 diabetes, and slightly higher for those with an increased risk of hypoglycaemia (Table 2) [38] (D), [39] (D). If sensor glucose is expected to increase, as often seen in people performing fasted high-intensity interval training [55,56], resistance training [49,65,66] and, also, in training above the anaerobic threshold [67], then an insulin correction can be administered at the onset of, as well as during exercise (50% of typical correction factor) [68] (D), [69] (D). ...
... resistance, aerobic, high-intensity intervals), intensity and duration of the exercise sessions. We have also recently seen that blood glucose responses during and after fasting morning exercise are different from those seen during postprandial, late afternoon exercise (9). Considering the level of complexity in trying to model these changes accurately, exercise continues to be one of the more difficult hurdles in the development of a successful artificial pancreas system (10). ...
... The Ottawa study (3) was approved by the research ethics boards (REBs) of the University of Ottawa and the Ottawa Hospitals. The Edmonton study (22) was approved by the University of Alberta's human REB. Informed consent for secondary use of previously collected data was obtained from all participants. ...
Objectives:
In adults with type 1 diabetes, resistance exercise (RE) is associated with more stable blood glucose (BG) levels than aerobic exercise, both during and after exercise. In individuals without diabetes, growth hormone and epinephrine responses to RE differ between the sexes. These hormones are known to affect BG levels in individuals with type 1 diabetes. In this study, we explored whether sex-related differences may exist in BG responses to RE in individuals with type 1 diabetes.
Methods:
A secondary data analysis was conducted on pooled data from 2 studies with identical RE protocols for individuals with type 1 diabetes (13 males, age range 16 to 63 years; 10 females, age range 19 to 45 years). The RE session consisted of 7 resistance-based exercises performed at 5 pm. Plasma glucose samples were collected before, immediately after and 1 h after exercise. Interstitial glucose levels were recorded through blinded continuous glucose monitoring 24 h before, during and 24 h after exercise.
Results:
There was a significant sex-by-time interaction (p<0.001) in plasma glucose responses to RE. Plasma glucose decreased significantly in males from 8.6±2.5 to 6.3±2.1 mmol/L (p<0.001) during exercise, whereas females experienced no significant change (7.2±1.3 to 7.3±1.3 mmol/L, p=0.999). In the 6 h after RE, males developed significantly more hypoglycemia, as measured by continuous glucose monitoring (p=0.048).
Conclusions:
Males may have a greater risk of hypoglycemia with an acute bout of RE than females. Further research is needed to examine this phenomenon more closely, as sex-specific recommendations for preventing hypoglycemia around RE may be necessary in type 1 diabetes.
The benefits of regular exercise in children and young people (CYP) with type 1 diabetes (T1D) are undisputed. Although encouraged, the total amount of exercise in this cohort remains suboptimal, with uncertainty of glycaemic response a barrier to exercise involvement. The bulk of the exercise literature for T1D concentrates on aerobic activities, but resistance exercise (RE) must not be overlooked. There are many benefits of RE – including physiological, psychological, musculoskeletal and cardiovascular effects – and emerging evidence highlights the possible glucose‐stabilising impact for individuals with T1D. In this review we describe the evidence base for the safety and benefits of RE in CYP with T1D, alongside strategies for optimising glycaemic management when engaging in this exercise modality, to minimise perceived barriers. Copyright © 2024 John Wiley & Sons.
ZUSAMMENFASSUNG
Bewegung ist für alle Formen des Diabetes mellitus eine der wichtigsten Maßnahmen, die Gesundheit zu erhalten. Regelmäßige körperliche Aktivität, möglichst uniform und täglich, kann vergleichbare Stoffwechseleffekte induzieren und somit die Glukoseregulation langfristig optimieren. Dabei ist die konkrete Blutzuckerantwort jedes Einzelnen abhängig von vielen Faktoren und muss bei Neubeginn von sportlicher Aktivität durch regelmäßige Blutzuckermessungen sowohl während als auch bis zu 12 h nach der Aktivität erfasst werden. Um bei älteren Menschen Erfolg zu haben, müssen Bewegungsprogramme deren körperliche Fähigkeiten, altersbedingten Leistungsabbau und krankheitsbedingte Beeinträchtigungen berücksichtigen. Die Nutzung von Geräten zur kontinuierlichen Glukosemessung (CGM) mit und ohne Insulinpumpentherapie hat viele Patienten in die Lage versetzt, die metabolische Kontrolle bei Bewegung und Sport besser zu überwachen, zu kontrollieren und zu optimieren. Die individuelle Blutzuckerreaktion auf verschiedene körperliche Belastungen ist mittels CGM leichter erlernbar, und Hypoglykämien sind früher vorhersag- und behandelbar. Ausdauerorientierte Bewegungsprogramme sollen primär die aerobe Kapazität steigern und sind aufgrund der positiven metabolischen und kardiopulmonalen Effekte eine gute Trainingsart. Auch ein Krafttraining für die großen Muskelgruppen kann (zusätzlich) empfohlen werden, da die Kraftbelastungen zu einer Zunahme der Muskel- und somit fettfreien Masse führen, resultierend in einer verbesserten Insulinresistenz. Zusätzlich sollte die Alltagsaktivität (Treppensteigen, Spazierengehen, Gartenarbeit etc.) gesteigert werden.
Aim:
The aim of the current study was to compare glucose responses when remotely supervised exercise was performed before or after breaking the fast, during Ramadan, in people with type 1 diabetes.
Methods:
People with type 1 diabetes were recruited to this randomised cross over design study, which took place in Kuwait during Ramadan in 2021-2022. Interstitial glucose was measured using continuous glucose monitors during a baseline week of normal activity and during weeks where remotely supervised exercise was performed, three times per week, either before (afternoon) or after (evening) breaking the fast, in a randomised crossover design. Exercise involved resistance and aerobic exercise and was supervised during a video call.
Results:
Thirty-two participants were recruited to the study (age 34(9) years and BMI 26(4)kg/m2). Mean interstitial glucose levels were lower on exercise days, compared to equivalent days in the baseline week, during both afternoon (8.6(1.8) mmol/L vs 9.1(1.4) mmol/L, p = 0.035) and evening (8.7(1.8) mmol/L vs 9.6(1.8) mmol/L, p < 0.001) exercise weeks. Mean glucose levels were lower the day after exercise, relative to both baseline (p < 0.001) and exercise (p = 0.011) days, in the evening exercise week only.
Conclusions:
Remotely supervised exercise performed during Ramadan can safely reduce interstitial glucose levels and may be of greater benefit when performed in the evening, further work is required to confirm this in a larger trial.
Exercise is a cornerstone of diabetes self-care because of its association with many health benefits. Several studies that have explored the best time of day to exercise to inform clinical recommendations have yielded mixed results. For example, for people with prediabetes or type 2 diabetes, there may be benefits to timing exercise to occur after meals, whereas people with type 1 diabetes may benefit from performing exercise earlier in the day. One common thread is the health benefits of consistent exercise, suggesting that the issue of exercise timing may be secondary to the goal of helping people with diabetes establish an exercise routine that best fits their life.
Exercise plays an important role in the management of diabetes and is associated with many benefits such as decreased morbidity and mortality. For people exhibiting signs and symptoms of cardiovascular disease, pre-exercise medical clearance is warranted; however, requiring broad screening requirements can lead to unnecessary barriers to initiating an exercise program. Robust evidence supports the promotion of both aerobic and resistance training, with evidence emerging on the importance of reducing sedentary time. For people with type 1 diabetes, there are special considerations, including hypoglycemia risk and prevention, exercise timing (including prandial status), and differences in glycemic responses based on biological sex.
Objectives:
To compare the effect of a single bout of morning vs. evening exercise on cardiovascular risk factors in adults.
Design:
Systematic review and meta-analysis.
Methods:
A systematic search of studies was conducted using PubMed and Web of Science from inception to June 2022. Selected studies accomplished the following criteria: crossover design, acute effect of exercise, blood pressure, blood glucose, and/or blood lipids as the study's endpoint, a washout period of at least 24 h, and adults. Meta-analysis was performed by analyzing: 1) separated effect of morning and evening exercise (pre vs. post); and 2) comparison between morning and evening exercise.
Results:
A total of 11 studies were included for systolic and diastolic blood pressure and 10 studies for blood glucose. Meta-analysis revealed no significant difference between morning vs. evening exercise for systolic blood pressure (g ∆ = 0.02), diastolic blood pressure (g ∆ = 0.01), or blood glucose (g ∆ = 0.15). Analysis of moderator variables (age, BMI, sex, health status, intensity and duration of exercise, and hour within the morning or evening) showed no significant morning vs. evening effect.
Conclusions:
Overall, we found no influence of the time of the day on the acute effect of exercise on blood pressure neither on blood glucose.
Introduction
Exercise-induced hyperglycemia is recognized in type 1 diabetes (T1D) clinical guidelines, but its association with high intensity intermittent exercise (HIIE) in acute studies is inconsistent. This meta-analysis examined the available evidence of blood glucose responses to HIIE in adults with T1D. The secondary aim was to examine predictors of blood glucose responses to HIIE. We hypothesized that there would be no consistent effect on blood glucose from HIIE, unless examined in the context of participant prandial status.
Methods
We conducted a literature search using keywords related to T1D and HIIE. Studies were required to include at least 6 participants with T1D with mean age >18 years, involve a HIIE intervention, and contain pre- and post-exercise measures of blood glucose. Analyses of extracted data were performed using a general inverse variance statistical method with a random effects model and a weighted multiple regression.
Results
Nineteen interventions from 15 reports were included in the analysis. A mean overall blood glucose change of -1.3 mmol/L (95% confidence interval [-2.3, -0.2]) was found during exercise albeit with high heterogeneity (I²= 84%). When performed following an overnight fast, exercise increased blood glucose by +1.7 mmol/L [0.4, 3.0], while post-prandial exercise decreased blood glucose by -2.1 mmol/L [-2.8, -1.4], with a statistically significant difference between groups (p<0.0001). No associations with fitness (p=0.4), sex (p=0.4), age (p=0.9), exercise duration (p=0.9), or interval duration (p=0.2) were found.
Conclusion
The effect of HIIE on blood glucose is inconsistent, but partially explained by prandial status.
Regular physical activity improves cardiometabolic and musculoskeletal health, helps with weight management, improves cognitive and psychosocial functioning, and is associated with reduced mortality related to cancer and diabetes mellitus. However, turnover rates of glucose in the blood increase dramatically during exercise, which often results in either hypoglycaemia or hyperglycaemia as well as increased glycaemic variability in individuals with type 1 diabetes mellitus (T1DM). A complex neuroendocrine response to an acute exercise session helps to maintain circulating levels of glucose in a fairly tight range in healthy individuals, while several abnormal physiological processes and limitations of insulin therapy limit the capacity of people with T1DM to exercise in a normoglycaemic state. Knowledge of the acute and chronic effects of exercise and regular physical activity is critical for the formulation of clinical strategies for the management of insulin and nutrition for active patients with T1DM. Emerging diabetes-related technologies, such as continuous glucose monitors, automated insulin delivery systems and the administration of solubilized glucagon, are demonstrating efficacy for preserving glucose homeostasis during and after exercise in this population of patients. This Review highlights the beneficial effects of regular exercise and details the complex endocrine and metabolic responses to different types of exercise for adults with T1DM. An overview of basic clinical strategies for the preservation of glucose homeostasis using emerging technologies is also provided.
The scientific literature shows that exercise has many benefits for individuals with type 1 diabetes. Yet, several barriers to exercise in this population exist, such as post-exercise hypoglycaemia or hyperglycaemia. Several studies suggest that the timing of exercise may be an important factor in preventing exercise-induced hypoglycaemia or hyperglycaemia. However, there is a paucity of evidence solely focused on summarising findings regarding exercise timing and the impact it has on glucose metabolism in type 1 diabetes. This report suggests that resistance or high-intensity interval exercise/training (often known as HIIT) may be best commenced at the time of day when an individual is most likely to experience a hypoglycaemic event (i.e., afternoon/evening) due to the superior blood glucose stability resistance and HIIT exercise provides. Continuous aerobic-based exercise is advised to be performed in the morning due to circadian elevations in blood glucose at this time, thereby providing added protection against a hypoglycaemic episode. Ultimately, the evidence concerning exercise timing and glycaemic control remains at an embryonic stage. Carefully designed investigations of this nexus are required, which could be harnessed to determine the most effective, and possibly safest, time to exercise for those with type 1 diabetes.
AIM To assess evening and overnight hypoglycemia risk following late afternoon exercise compared with a non-exercise control day in adults with type 1 diabetes using automated insulin delivery (AID). METHODS Thirty adults with type 1 diabetes (Mean [SD] Age 38[9] Years; 14Female; HbA1c 7.1[1.0] % / 54[11 ] mmol/mol ) using AID (Minimed 670G) performed in random order 40-minutes high-intensity (HIE), resistance (RE), and moderate-intensity (MIE) exercise each separated by >1 week. Exercise commenced at ~16:00. A standardized meal was eaten at ~20:40. Hypoglycemic events were defined as a continuous glucose monitor (CGM) reading <70mg/dL for ≥15 min. Four-hour post-evening meal and overnight (MN-06:00) CGM metrics for exercise were compared with the prior non-exercise (control) day. RESULTS There was no severe hypoglycemia. Between 00:00-06:00, the proportion of nights with hypoglycemia did not differ post-exercise vs control for HIE (18% vs. 11%; p=0.688), RE (4% vs. 14%; p=0.375) and MIE (7% vs. 14%; p=0.625). Time in Range (70-180mg/dL), >75% for all nights, did not differ between exercise conditions and control. Hypoglycemia episodes post-meal following exercise vs. control did not differ for HIE (22% vs 7%; p=0.219) and MIE (10% vs. 14%; p>0.999) but were greater post RE (39% vs. 10%; p=0.012). CONCLUSIONS Overnight TIR was excellent with AID without an increase in hypoglycemia post-exercise between 00:00-06:00 compared with non-exercise days. In contrast the risk for hypoglycemia was increased following the first meal post-RE, suggesting the importance of greater vigilance and specific guidelines for meal-time dosing, particularly with vigorous RE.
Exercise and physical activity are important tools in the management of both type 1 and type 2 diabetes due, in part, to their ability to decrease risk factors associated with diabetes-related complications and improve overall health. Like any other treatment, however, a great deal of interindividual and intraindividual variation exists in responses to different activity doses (type, timing, intensity, frequency, and duration). This chapter provides an overview of the factors that may influence both short- and long-term adaptation to exercise and physical activity in individuals with both type 1 and type 2 diabetes so that the right treatment, for the right person, at the right time can be combined in developing an appropriate exercise/physical activity prescription.KeywordsAerobic exerciseResistance exerciseHigh-intensity intermittent exerciseBlood glucoseInsulinA1c
Exercise and physical activity are essential to longevity and health in individuals with type 1 diabetes (T1D). Due to the risk of hypoglycemia (low blood glucose levels), special considerations need to be made around the type, timing, and intensity of exercise, as these will all have different impacts on blood glucose levels both during and after the activity. To mitigate the risk of hypoglycemia, adjustments to insulin dosage can be made before, as well as after, either in place of or in addition to the consumption of extra carbohydrates. Additional special considerations will be necessary for the presence of diabetes complications, such as nephropathy, neuropathy, retinopathy, or cardiovascular disease. Otherwise, individuals with T1D should aim to obtain the same amount of physical activity (and avoid the same amount of sedentary time) as prescribed for those in their age group without diabetes since they will obtain the same health benefits from being active.
Objective:
To compare glucose control with hybrid closed-loop (HCL) when challenged by high intensity exercise (HIE), moderate intensity exercise (MIE), and resistance exercise (RE) while profiling counterregulatory hormones, lactate, ketones, and kinetic data in adults with type 1 diabetes.
Research design and methods:
Open-label multisite randomized crossover trial. Adults with type 1 diabetes undertook 40 min of HIE, MIE, and RE in random order while using HCL (Medtronic MiniMedTM 670G) with a temporary target set 2 h prior to and during exercise and 15 g carbohydrates if pre-exercise glucose was <126 mg/dL to prevent hypoglycemia. Primary outcome was median (interquartile range) continuous glucose monitoring time-in-range (TIR; 70-180 mg/dL) for 14 h post-exercise commencement. Accelerometer data and venous glucose, ketones, lactate, and counterregulatory hormones were measured for 280 min post-exercise commencement.
Results:
Median TIR was 81% (67, 93%), 91% (80, 94%), and 80% (73, 89%) for 0-14 h post-exercise commencement for HIE, MIE, and RE, respectively (n = 30), with no difference between exercise types (MIE vs. HIE; P = 0.11, MIE vs. RE, P = 0.11; and HIE vs. RE, P = 0.90). Time-below-range was 0% for all exercise bouts. For HIE and RE compared with MIE, there were greater increases, respectively, in noradrenaline (P = 0.01 and P = 0.004), cortisol (P < 0.001 and P = 0.001), lactate (P ≤ 0.001 and P ≤ 0.001), and heart rate (P = 0.007 and P = 0.015). During HIE compared with MIE, there were greater increases in growth hormone (P = 0.024).
Conclusions:
Under controlled conditions, HCL provided satisfactory glucose control with no difference between exercise type. Lactate, counterregulatory hormones, and kinetic data differentiate type and intensity of exercise, and their measurement may help inform insulin needs during exercise. However, their potential utility as modulators of insulin dosing will be limited by the pharmacokinetics of subcutaneous insulin delivery.
The circadian rhythmicity of endogenous metabolic and hormonal processes is controlled by a complex system of central and peripheral pacemakers, influenced by exogenous factors like light/dark-cycles, nutrition and exercise timing. There is evidence that alterations in this system may be involved in the pathogenesis of metabolic diseases. It has been shown that disruptions to normal diurnal rhythms lead to drastic changes in circadian processes, as often seen in modern society due to excessive exposure to unnatural light sources. Out of that, research has focused on time-restricted feeding and exercise, as both seem to be able to reset disruptions in circadian pacemakers. Based on these results and personal physical goals, optimal time periods for food intake and exercise have been identified. This review shows that appropriate nutrition and exercise timing are powerful tools to support, rather than not disturb, the circadian rhythm and potentially contribute to the prevention of metabolic diseases. Nevertheless, both lifestyle interventions are unable to address the real issue: the misalignment of our biological with our social time.
Continuous Glucose Monitoring (CGM) has been a springboard of new diabetes management technologies such as integrated sensor-pump systems, the artificial pancreas, and more recently, smart pens. It also allows patients to make better informed decisions compared to a few measurements per day from a glucometer. However, CGM accuracy is reportedly affected during exercise periods, which can impact the effectiveness of CGM-based treatments. In this review, several studies that used CGM during exercise periods are scrutinized. An extensive literature review of clinical trials including exercise and CGM in type 1 diabetes was conducted. The gathered data were critically analysed, especially the Mean Absolute Relative Difference (MARD), as the main metric of glucose accuracy. Most papers did not provide accuracy metrics that differentiated between exercise and rest (non-exercise) periods, which hindered comparative data analysis. Nevertheless, the statistic results confirmed that CGM during exercise periods is less accurate.
Objectives
In individuals with type 1 diabetes (T1D), changes in blood glucose (BG) during high-intensity interval exercise (HIIE) are smaller than those observed during aerobic exercise. Study outcomes, however, have been variable, with some demonstrating significant BG decreases and others showing BG increases. This study compared BG outcomes between fasting (AME) and postprandial (PME) HIIE in T1D to test the hypothesis that AME would produce a BG increase, yet PME would cause BG to decline.
Methods
Twelve (6 men and 6 women) physically active individuals with T1D performed two 45-minute exercise sessions (AME at 7:00 AM, PME at 5:00 PM) in random order, separated by at least 48 hours. Sessions consisted of a 10-minute warmup (50%VO2peak), followed by 10-second sprints every 2 minutes for 24 minutes, and then an 11-minute cooldown. Capillary glucose was measured pre- and postexercise, and then 60 minutes postexercise. Interstitial glucose was recorded for 24 hours postexercise using continuous glucose monitoring.
Results
AME caused capillary glucose to increase (from 7.6±1.4 to 9.2±2.9 mmol/L during exercise, and 9.9±2.8 mmol/L in recovery), whereas PME produced a decline in capillary glucose (from 9.9±3.1 to 9.5±3.4 mmol/L during exercise and 8.9±2.7 mmol/L during recovery; time × treatment interaction, p=0.014). PME was associated with a higher frequency of hyperglycemic events in the 6 hours and overnight (midnight to 6:00 AM) after exercise.
Conclusions
Fasting HIIE results in a different BG trajectory than postprandial exercise in T1D, and may be beneficial for hypoglycemia avoidance during exercise.
Background:
To analyze key indicators of metabolic control in adults with type 1 diabetes (T1D) using real-time or intermittent scanning continuous glucose monitoring (rtCGM/iscCGM) during real-life care, based on the German/Austrian/Swiss Prospective Diabetes Follow-up (DPV) registry.
Methods:
Cross-sectional analysis including 233 adults with T1D using CGM. We assessed CGM metrics by sex, age group (18-<30 vs. ≥30years), insulin delivery method (MDI vs. CSII) and sensor type (iscCGM vs. rtCGM), working days vs. weekends, and daytime vs. night-time using multivariable linear regression models (adjusted for demographic variables) or Wilcoxon signed-rank test.
Results:
Overall, 79/21% of T1D patients used iscCGM/rtCGM. Those aged ≥30 years spent more time in target range (TIR [70-180 mg/dL] 54 vs. 49%) and hypoglycemic range <70 mg/dL (7 vs. 5%), less time in hyperglycemic range >180 mg/dL (38 vs. 46%) and had a lower glucose variability (CV 36 vs. 37%) compared with adults aged <30 years. We found no significant differences between the sexes. Multivariable regression models revealed the highest TIR and lowest time with sensor glucose >250 mg/dL, CV and daytime-night-time differences in those treated with CSII and rtCGM. Glucose profiles were slightly more favorable on working days.
Conclusions:
In our real-world data, rtCGM vs. iscCGM was associated with a higher percentage of TIR and improved metabolic stability. Differences in ambulatory glucose profiles on working and weekend days may indicate lifestyle habits affecting glycemic stability. Real-life CGM results should be included in benchmarking-reports in addition to HbA1c and history of hypoglycemia.
Background:
Exercise causes glycemic disturbances in individuals with type 1 diabetes (T1D). Continuous moderate-intensity aerobic exercise (CON) generally lowers blood glucose (BG) levels and often leads to hypoglycemia. In comparison, circuit-based exercise (CIRC) may attenuate the drop in BG. The goal of this study is to contrast the effects of basal insulin suspension at the onset of two different forms of exercise (CON vs. CIRC).
Methods:
Twelve individuals (six men and six women) with T1D on insulin pump therapy were recruited for the study. All participants completed a maximal aerobic fitness test and two 40-min exercise sessions, consisting of either continuous treadmill walking or a circuit workout. Basal insulin infusion was stopped at the onset of exercise and resumed in recovery. After providing an initial reference value, volunteers were blinded to their [BG] and were asked to estimate their levels during exercise.
Results:
Oxygen consumption (47.5 ± 7.5 vs. 54.5 ± 13.5 mL·kg-1·min-1, P = 0.03) and heart rate (122 ± 20 vs. 144 ± 20 bpm, P = 0.003) were lower in CON vs. CIRC. Despite the lower workload, BG levels dropped more with CON vs. CIRC (delta BG = -3.8 ± 1.5 vs. -0.5 ± 3.0 mmol/L for CON vs. CIRC, respectively, P = 0.001). Participants were able to estimate their BG more accurately during CON (r = 0.83) vs. CIRC (r = 0.33) based on a regression analysis.
Conclusion:
Despite a lower intensity of exercise, with full basal insulin suspension at the start of exercise, CON results in a larger drop in BG vs. CIRC. These findings have implications for single hormone-based artificial pancreas development for exercise. While this study does not negate the importance of frequent capillary BG monitoring during exercise, it does suggest that if persons are knowledgeable about their pre-exercise BG levels, they can accurately perceive the changes in BG during CON, but not during CIRC.
We investigated blood glucose (BG) and hormone response to aerobic high-intensity interval exercise (HIIE) and moderate continuous exercise (CON) matched for mean load and duration in type 1 diabetes mellitus (T1DM).
Material and Methods
Seven trained male subjects with T1DM performed a maximal incremental exercise test and HIIE and CON at 3 different mean intensities below (A) and above (B) the first lactate turn point and below the second lactate turn point (C) on a cycle ergometer. Subjects were adjusted to ultra-long-acting insulin Degludec (Tresiba/ Novo Nordisk, Denmark). Before exercise, standardized meals were administered, and short-acting insulin dose was reduced by 25% (A), 50% (B), and 75% (C) dependent on mean exercise intensity. During exercise, BG, adrenaline, noradrenaline, dopamine, cortisol, glucagon, and insulin-like growth factor-1, blood lactate, heart rate, and gas exchange variables were measured. For 24 h after exercise, interstitial glucose was measured by continuous glucose monitoring system.
Results
BG decrease during HIIE was significantly smaller for B (p = 0.024) and tended to be smaller for A and C compared to CON. No differences were found for post-exercise interstitial glucose, acute hormone response, and carbohydrate utilization between HIIE and CON for A, B, and C. In HIIE, blood lactate for A (p = 0.006) and B (p = 0.004) and respiratory exchange ratio for A (p = 0.003) and B (p = 0.003) were significantly higher compared to CON but not for C.
Conclusion
Hypoglycemia did not occur during or after HIIE and CON when using ultra-long-acting insulin and applying our methodological approach for exercise prescription. HIIE led to a smaller BG decrease compared to CON, although both exercises modes were matched for mean load and duration, even despite markedly higher peak workloads applied in HIIE. Therefore, HIIE and CON could be safely performed in T1DM.
We compared growth hormone (GH) and plasma glucose (PG) levels in type 1 diabetic individuals performing aerobic before resistance exercise (AR) to when resistance exercise was performed first (RA). In AR, GH secretion declined in late exercise while it rose throughout exercise in RA, resulting in higher GH in RA versus AR at exercise completion. Higher GH during RA may support PG by increasing hepatic glucose production and lipid mobilization.
Objective
The goal was to develop a new index of insulin sensitivity in patients with type 1 diabetes estimated from continuous glucose monitoring (CGM) and subcutaneous insulin delivery data under carefully controlled conditions.Research Design & Methods
The data base consists of 12 subjects with type 1 diabetes, studied during breakfast, lunch and dinner, in a clinical research unit, wearing both subcutaneous insulin pump and CGM. Frequent blood samples were drawn for measurements of plasma glucose and insulin concentrations in order to estimate insulin sensitivity with the oral minimal model (SI(MM)). The new index of insulin sensitivity (SI(SP)) was calculated with a simple algebraic formula, for each meal, using only CGM and insulin pump data and compared with SI(MM).ResultsSI(SP) was well correlated with SI(MM) (r = 0.825, p<10(-8)) and diurnal pattern was also similar to SI(MM).ConclusionA novel method for estimating insulin sensitivity in subjects with type 1 diabetes on sensor augmented insulin pump therapy has been presented. This new index correlates well with the reference oral minimal model estimate of insulin sensitivity. The knowledge of patient-specific insulin sensitivity and its diurnal variation can help in optimizing insulin therapy in type 1 diabetes and could also inform the next generation closed-loop control systems.
Although trials have shown that exercise has positive effects on bone mineral density (BMD), the majority of exercise trials have been conducted in older women. The aim of this study was to systematically review trials examining the effect of weight-bearing and resistance-based exercise modalities on the BMD of hip and lumbar spine of middle-aged and older men. Eight electronic databases were searched in August 2012. Randomised controlled or controlled trials that assessed the effect of weight-bearing and resistance-based exercise interventions on BMD measured by dual-energy x-ray absorptiometry, and reported effects in middle-aged and older men were included. Eight trials detailed in nine papers were included. The interventions included walking (n = 2), resistance training (n = 3), walking + resistance training (n = 1), resistance training + impact-loading activities (n = 1) and resistance training + Tai Chi (n = 1). Five of the eight trials achieved a score of less than 50 % on the modified Delphi quality rating scale. Further, there was heterogeneity in the type, intensity, frequency and duration of the exercise regimens. Effects of exercise varied greatly among studies, with six interventions having a positive effect on BMD and two interventions having no significant effect. It appears that resistance training alone or in combination with impact-loading activities are most osteogenic for this population, whereas the walking trials had limited effect on BMD. Therefore, regular resistance training and impact-loading activities should be considered as a strategy to prevent osteoporosis in middle-aged and older men. High quality randomised controlled trials are needed to establish the optimal exercise prescription.
We have recently demonstrated a diurnal pattern to insulin action (SI) in healthy individuals with higher SI at breakfast than dinner. To determine if such a pattern exists in type 1 diabetes we studied 19 C-peptide negative subjects (HbA1c 7.1±0.6%) on insulin pump therapy with normal gastric emptying. Identical mixed meals were ingested during breakfast (B), lunch (L) or dinner (D) at 0700, 1300 and 1900 in randomized Latin Square order on three consecutive days when measured daily physical activity was equal. The triple tracer technique enabled measurement of glucose fluxes. Insulin was administered according to the customary insulin:carbohydrate ratio for each participant. While postprandial glucose excursions did not differ among meals, insulin concentration was higher (p<0.01) and endogenous glucose production less suppressed (p<0.049) at B than L. There were no differences in meal glucose appearance or glucose disappearance between meals. Although there was no statistical difference (p=0.34) in SI between meals in type 1 diabetes participants, the diurnal pattern of SI taken across the three meals in its entirety, did differ (p=0.016) from healthy subjects. While the pattern in healthy subjects showed decreasing SI between B and L, the reverse SI pattern was observed in type 1 diabetes. The results suggest that in contrast to healthy subjects, SI diurnal pattern in type 1 diabetes is individual specific, hence cannot be extrapolated to the type 1 diabetes population as a whole thus implying that Artificial Pancreas algorithms may need to be personalized.
OBJECTIVE
In type 1 diabetes, small studies have found that resistance exercise (weight lifting) reduces HbA(1c). In the current study, we examined the acute impacts of resistance exercise on glycemia during exercise and in the subsequent 24 h compared with aerobic exercise and no exercise.RESEARCH DESIGN AND METHODS
Twelve physically active individuals with type 1 diabetes (HbA(1c) 7.1 ± 1.0%) performed 45 min of resistance exercise (three sets of seven exercises at eight repetitions maximum), 45 min of aerobic exercise (running at 60% of Vo(2max)), or no exercise on separate days. Plasma glucose was measured during and for 60 min after exercise. Interstitial glucose was measured by continuous glucose monitoring 24 h before, during, and 24 h after exercise.RESULTSTreatment-by-time interactions (P < 0.001) were found for changes in plasma glucose during and after exercise. Plasma glucose decreased from 8.4 ± 2.7 to 6.8 ± 2.3 mmol/L (P = 0.008) during resistance exercise and from 9.2 ± 3.4 to 5.8 ± 2.0 mmol/L (P = 0.001) during aerobic exercise. No significant changes were seen during the no-exercise control session. During recovery, glucose levels did not change significantly after resistance exercise but increased by 2.2 ± 0.6 mmol/L (P = 0.023) after aerobic exercise. Mean interstitial glucose from 4.5 to 6.0 h postexercise was significantly lower after resistance exercise versus aerobic exercise.CONCLUSIONS
Resistance exercise causes less initial decline in blood glucose during the activity but is associated with more prolonged reductions in postexercise glycemia than aerobic exercise. This might account for HbA(1c) reductions found in studies of resistance exercise but not aerobic exercise in type 1 diabetes.
To determine the effects of exercise order on acute glycemic responses in individuals with type 1 diabetes performing both aerobic and resistance exercise in the same session.
Twelve physically active individuals with type 1 diabetes (HbA(1c) 7.1 ± 1.0%) performed aerobic exercise (45 min of running at 60% V(O(2peak))) before 45 min of resistance training (three sets of eight, seven different exercises) (AR) or performed the resistance exercise before aerobic exercise (RA). Plasma glucose was measured during exercise and for 60 min after exercise. Interstitial glucose was measured by continuous glucose monitoring 24 h before, during, and 24 h after exercise.
Significant declines in blood glucose levels were seen in AR but not in RA throughout the first exercise modality, resulting in higher glucose levels in RA (AR = 5.5 ± 0.7, RA = 9.2 ± 1.2 mmol/L, P = 0.006 after 45 min of exercise). Glucose subsequently decreased in RA and increased in AR over the course of the second 45-min exercise bout, resulting in levels that were not significantly different by the end of exercise (AR = 7.5 ± 0.8, RA = 6.9 ± 1.0 mmol/L, P = 0.436). Although there were no differences in frequency of postexercise hypoglycemia, the duration (105 vs. 48 min) and severity (area under the curve 112 vs. 59 units ⋅ min) of hypoglycemia were nonsignificantly greater after AR compared with RA.
Performing resistance exercise before aerobic exercise improves glycemic stability throughout exercise and reduces the duration and severity of postexercise hypoglycemia for individuals with type 1 diabetes.
With the aging of the baby-boom generation and increases in life expectancy, the American population is growing older. Aging is associated with adverse changes in glucose tolerance and increased risk of diabetes; the increasing prevalence of diabetes among older adults suggests a clear need for effective diabetes prevention approaches for this population. The purpose of paper is to review what is known about changes in glucose tolerance with advancing age and the potential utility of resistance training (RT) as an intervention to prevent diabetes among middle-aged and older adults. Age-related factors contributing to glucose intolerance, which may be improved with RT, include improvements in insulin signaling defects, reductions in tumor necrosis factor-α, increases in adiponectin and insulin-like growth factor-1 concentrations, and reductions in total and abdominal visceral fat. Current RT recommendations and future areas for investigation are presented.
Exercise is a cornerstone of diabetes therapy in type 1 diabetes mellitus (DMT1) patients. The type of exercise is important in determining the propensity to hypoglycemia. We assessed, by continuous glucose monitoring (CGM), the glucose profiles during and in the following 20h after a session of two different types of exercise.
Eight male volunteers with well-controlled DMT1 were studied. They underwent 30min of both intermittent high-intensity exercise (IHE) and moderate-intensity exercise (MOD) in random order. Expired air was recorded during exercise, while metabolic and hormonal determinations were performed before and for 120 min after exercises. The CGM system and activity monitor were applied for the subsequent 20h.
Blood glucose level declined during both type of exercise. At 150 min following the start of exercise, plasma glucose content was slightly higher after IHE. No changes were observed in plasma insulin concentration. A significant increase of norepinephrine concentration was noticed during IHE. Between midnight and 6:00 a.m. the glucose levels were significantly lower after IHE than those observed after MOD (area under the curve, 23.3 ± 3 vs. 16 ± 3 mg/dL/420 min [P = 0.04]; mean glycemia at 3 a.m., 225 ± 31 vs. 147 ± 17 mg/dL [P<0.05]). The number of hypoglycemic episodes after IHE was higher than that observed after MOD (seven vs. two [P<0.05]).
We demonstrate that (1) CGM is a useful approach in DMT1 patients who undergo an exercise program and (2) IHE is associated with delayed nocturnal hypoglycemia.
Little information is available regarding the optimal timing of exercise in insulin-dependent diabetes mellitus (IDDM) patients. In this study, six IDDM patients receiving ultralente-based intensive insulin therapy were studied during 30 min of exercise (approximately 60% VO2max), before breakfast, and at 1600. On two other occasions, they were studied at rest. Plasma glucose increased from 6.7 +/- 0.4 to 9.1 +/- 0.4 mM during morning exercise (P less than 0.01). In contrast, mean plasma glucose did not change during afternoon exercise (delta = 0.3 +/- 0.5 mM, NS); however, there was a 0.3- to 1.0-mM decrease in three subjects. The observed difference in the glycemic response to exercise could not be explained on the basis of changes in plasma glucagon, growth hormone, norepinephrine, or epinephrine. Plasma cortisol was higher (P less than 0.02) in the morning than in the afternoon, and plasma free-insulin concentrations were lower (P less than 0.05). These data indicate that the risk of exercise-induced hypoglycemia is lowest before breakfast. The reason for the divergent glycemic responses to exercise is not entirely clear but may be related to the observed differences in free-insulin concentrations. Because of the lower risk of hypoglycemia, our results suggest prebreakfast exercise may be preferable for some IDDM patients receiving intensive insulin therapy. Whether these findings are relevant to patients receiving other types of insulin therapy will require further investigation.
Eleven insulin-dependent (type I) diabetic subjects were studied during a 24-h period to assess intraday blood glucose (BG) variation and related free insulin (FI) levels. Ten patients exhibited the dawn phenomenon, a rise in early morning fasting blood glucose (123 +/- 81.1 m/dl; mean +/- SD). This increase was positively and significantly correlated with the morning postprandial BG peak (r = 0.723; P = 0.012). FI/BG ratios were highest during the night (0.717 and 0.666 at 2200 and 0400 h, respectively) and lowest during the early morning (0.294 at 0800 h) (P less than 0.01). Three of the four observed hypoglycemic episodes occurred during the period when free insulin levels were high relative to BG. We conclude that the dawn phenomenon contributed directly and significantly to the BG maximum and indirectly, in some cases, to nocturnal hypoglycemia. It thus played an important role in the intraday blood glucose variation of such patients.
To investigate the effect of elevated plasma free fatty acid (FFA) concentrations on splanchnic glucose uptake (SGU), we measured SGU in nine healthy subjects (age, 44 +/- 4 yr; body mass index, 27.4 +/- 1.2 kg/m(2); fasting plasma glucose, 5.2 +/- 0.1 mmol/l) during an Intralipid-heparin (LIP) infusion and during a saline (Sal) infusion. SGU was estimated by the oral glucose load (OGL)-insulin clamp method: subjects received a 7-h euglycemic insulin (100 mU x m(-2) x min(-1)) clamp, and a 75-g OGL was ingested 3 h after the insulin clamp was started. After glucose ingestion, the steady-state glucose infusion rate (GIR) during the insulin clamp was decreased to maintain euglycemia. SGU was calculated by subtracting the integrated decrease in GIR during the period after glucose ingestion from the ingested glucose load. [3-(3)H]glucose was infused during the initial 3 h of the insulin clamp to determine rates of endogenous glucose production (EGP) and glucose disappearance (R(d)). During the 3-h euglycemic insulin clamp before glucose ingestion, R(d) was decreased (8.8 +/- 0.5 vs. 7.6 +/- 0.5 mg x kg(-1) x min(-1), P < 0.01), and suppression of EGP was impaired (0.2 +/- 0.04 vs. 0.07 +/- 0.03 mg x kg(-1) x min(-1), P < 0.01). During the 4-h period after glucose ingestion, SGU was significantly increased during the LIP vs. Sal infusion study (30 +/- 2 vs. 20 +/- 2%, P < 0.005). In conclusion, an elevation in plasma FFA concentration impairs whole body glucose R(d) and insulin-mediated suppression of EGP in healthy subjects but augments SGU.
This study examined the influence of prior endurance exercise on hormonal responses to subsequent resistance exercise. Ten males exercised on a cycle ergometer at 50% of maximal oxygen uptake for 60 min and subsequently completed a resistance exercise (bench and leg press, four sets at ten repetitions maximum with an interset rest period of 90 s). Alternatively, the subjects performed the protocol on a separate day with prior endurance exercise limited to 5 min. Blood was obtained before and after the endurance exercise, and 10, 20, and 30 min after the resistance exercise. Maximal isometric torque measured before and after endurance and resistance exercises showed no significant difference between trials. No significant difference was seen in the concentrations of glucose, lactate, testosterone, and cortisol between the trials, but free fatty acids (FFA) and growth hormone (GH) increased (P<0.01 and P<0.05, respectively) after 60 min of endurance exercise. Conversely, after the resistance exercise, GH was attenuated by 60 min of prior exercise (P<0.05). These results indicate that the GH response to resistance exercise is attenuated by prior endurance exercise. This effect might be caused by the increase in blood FFA concentration at the beginning of resistance exercise.
Aims
To compare the effect of a bout of high-intensity interval training (HIT) with a bout of moderate-intensity continuous training (MICT) on glucose concentrations over the subsequent 24h period.
METHODS
Fourteen people with type 1 diabetes (duration of type 1 diabetes 8.2±1.4 years), all on basal-bolus regimen, completed a randomised, counterbalanced, crossover study. Continuous glucose monitoring was used to assess glycaemic control following a single bout of HIT (6 x 1min intervals) and 30 mins of moderate-intensity continuous training (MICT) on separate days, compared to a non-exercise control day (CON). Exercise was undertaken following an overnight fast with omission of short-acting insulin. Capillary blood glucose samples were recorded pre and post-exercise to assess the acute changes in glycaemia during HIT and MICT.
RESULTS
There was no difference in the incidence of or percentage time spent in hypoglycaemia, hyperglycaemia or target glucose range over the 24h and nocturnal period (24:00-06:00h) between CON, HIT and MICT (P>0.05). Blood glucose concentrations were not significantly (P=0.49) different from pre to post-exercise with HIT (+0.39±0.42 mmol/L) or MICT (-0.39±0.66 mmol/L), with no difference between exercise modes (P=1.00).
CONCLUSIONS
HIT or 30 mins of MICT can be carried out after an overnight fast with no increased risk of hypoglycaemia or hyperglycaemia, and provided the pre-exercise glucose concentration is 7-14 mmol/L, no additional carbohydrate ingestion is necessary to undertake these exercises. As HIT is a time-efficient form of exercise, the efficacy and safety of long-term HIT should now be explored.
Type 1 diabetes is a challenging condition to manage for various physiological and behavioural reasons. Regular exercise is important, but management of different forms of physical activity is particularly difficult for both the individual with type 1 diabetes and the health-care provider. People with type 1 diabetes tend to be at least as inactive as the general population, with a large percentage of individuals not maintaining a healthy body mass nor achieving the minimum amount of moderate to vigorous aerobic activity per week. Regular exercise can improve health and wellbeing, and can help individuals to achieve their target lipid profile, body composition, and fitness and glycaemic goals. However, several additional barriers to exercise can exist for a person with diabetes, including fear of hypoglycaemia, loss of glycaemic control, and inadequate knowledge around exercise management. This Review provides an up-to-date consensus on exercise management for individuals with type 1 diabetes who exercise regularly, including glucose targets for safe and effective exercise, and nutritional and insulin dose adjustments to protect against exercise-related glucose excursions.
The adoption and maintenance of physical activity are critical foci for blood glucose management and overall health in individuals with diabetes and prediabetes. Recommendations and precautions vary depending on individual characteristics and health status. In this Position Statement, we provide a clinically oriented review and evidence-based recommendations regarding physical activity and exercise in people with type 1 diabetes, type 2 diabetes, gestational diabetes mellitus, and prediabetes.
We reviewed the effect of resistance training on blood pressure and other cardiovascular risk factors in adults. Randomized, controlled trials lasting ≥4 weeks investigating the effects of resistance training on blood pressure in healthy adults (age ≥18 years) and published in a peer-reviewed journal up to June 2010 were included. Random- and fixed-effects models were used for analyses, with data reported as weighted means and 95% confidence limits. We included 28 randomized, controlled trials, involving 33 study groups and 1012 participants. Overall, resistance training induced a significant blood pressure reduction in 28 normotensive or prehypertensive study groups [-3.9 (-6.4; -1.2)/-3.9 (-5.6; -2.2) mm Hg], whereas the reduction [-4.1 (-0.63; +1.4)/-1.5 (-3.4; +0.40) mm Hg] was not significant for the 5 hypertensive study groups. When study groups were divided according to the mode of training, isometric handgrip training in 3 groups resulted in a larger decrease in blood pressure [-13.5 (-16.5; -10.5)/-6.1(-8.3; -3.9) mm Hg] than dynamic resistance training in 30 groups [-2.8 (-4.3; -1.3)/-2.7 (-3.8; -1.7) mm Hg]. After dynamic resistance training, Vo(2) peak increased by 10.6% (P=0.01), whereas body fat and plasma triglycerides decreased by 0.6% (P<0.01) and 0.11 mmol/L (P<0.05), respectively. No significant effect could be observed on other blood lipids and fasting blood glucose. This meta-analysis supports the blood pressure-lowering potential of dynamic resistance training and isometric handgrip training. In addition, dynamic resistance training also favorably affects some other cardiovascular risk factors. Our results further suggest that isometric handgrip training may be more effective for reducing blood pressure than dynamic resistance training. However, given the small amount of isometric studies available, additional studies are warranted to confirm this finding.
The aim of this study was to compare the glycemic and glucoregulatory hormone responses to low- and moderate-intensity morning resistance exercise (RE) sessions in type 1 diabetes (T1DM). Following maximal strength assessments (1RM), eight T1DM (HbA1C :72 ± 12 mmol/mol, age:34 ± 7 years, body mass index:25.7 ± 1.6 kg/m(2) ) participants attended the research facility on two separate occasions, having fasted and taken their usual basal insulin but omitting rapid-acting insulin. Participants performed six exercises for two sets of 20 repetitions at 30%1RM during one session [low-intensity RE session (LOW)] and two sets of 10 repetitions at 60%1RM during another session [moderate-intensity RE session (MOD)], followed by 65-min recovery. Sessions were matched for total mass lifted (kg). Venous blood samples were taken before and after exercise. Data (mean ± SEM) were analyzed using analysis of variance (P ≤ 0.05). There were no hypoglycemic occurrences throughout the study. Blood glucose rose similarly between sessions during exercise (P = 0.382), remaining comparable between sessions throughout recovery (P > 0.05). There was no effect of RE intensity on metabolic acidosis (P > 0.05) or peak growth hormone responses (P = 0.644), but a tendency for greater catecholamine responses under LOW (individualized peak concentrations: adrenaline MOD 0.55 ± 0.13 vs LOW 1.04 ± 0.37 nmol/L, P = 0.155; noradrenaline MOD 4.59 ± 0.86 vs LOW 7.11 ± 1.82 nmol/L, P = 0.082). The magnitude of post-exercise hyperglycemia does not differ between equal volume low and moderate intensity RE sessions performed in the morning.
© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
To examine glycemic and glucoregulatory responses to resistance exercise (RE) sessions of different volume in type 1 diabetes (T1DM). Eight T1DM (seven males: one female; age: 38 ± 6 years, HbA1C: 8.7 ± 1.0%/71 ± 11 mmol/mol) attended the research facility fasted and on four separate occasions, having taken their usual basal insulin, but omitted morning rapid-acting insulin. Participants completed a 1SET (14 min), 2SET (28 min), 3SET (42 min) RE session (eight exercises × 10 repetitions) at 67 ± 3% one-repetition-maximum followed by 60-min recovery, or a resting trial (CON). Venous blood samples were taken before and after exercise. Data (mean ± SEM) were analyzed using repeated-measures analysis of variance (P ≤ 0.05). RE did not induce hypoglycemia (BG < 4 mmol/L). During recovery, blood glucose (BG) concentrations remained above pre-exercise after 1SET (15–60 min, P < 0.05) and 2SET (0–60 min, P < 0.05) but comparable (P > 0.05) with pre-exercise after 3SET. BGIAUC(area-under-curve) (mmol/L/60 min) was greater after 1SET and 2SET vs CON (1SET 103.6 ± 36.9 and 2SET 128.7 ± 26.1 vs CON −24.3 ± 15.2, P < 0.05), but similar between 3SET and CON (3SET 40.7 ± 59.3, P > 0.05). Under all trials, plasma creatine kinase levels at 24 h post-exercise were similar (P > 0.05) to pre-exercise. RE does not induce acute hypoglycemia or damage muscle. BG progressively rose after one and two sets of RE. However, inclusion of a third set attenuated exercise-induced hyperglycemia and returned BG to that of a non-exercise trial.
To compare the glycemic and metabolic responses to simulated intermittent games activity and continuous running exercise in type 1 diabetes. Nine patients (seven male, two female; 35 ± 4 years; HbA1c 8.1 ± 0.2%/65 ± 2 mmol/mol) treated on a basal-bolus regimen completed two main trials, a continuous treadmill run (CON) or an intermittent running protocol (INT). Patients arrived to the laboratory fasted at ∼ 08:00 h, replicating their usual pre-exercise meal and administering a 50% reduced dose of rapid-acting insulin before exercising. Blood glucose (BG), K+, Na++, pH, triglycerides, serum cortisol and NEFA were measured at baseline and for 60 min post-exercise. Interstitial glucose was measured for a further 23 h under free-living conditions. Following exercise, BG declined under both conditions but was less under INT (INT −1.1 ± 1.4 vs CON −5.3 ± 0.4 mmol/L, P = 0.037), meaning more patients experienced hypoglycemia (BG ≤ 3.5 mmol/L; CON n = 3 vs INT n = 2) but less hyperglycemia (BG ≥ 10.9 mmol/L; CON n = 0 vs INT n = 6) under CON. Blood lactate was significantly greater, and pH lower, with a temporal delay in K+ under INT (P < 0.05). No conditional differences were observed in other measures during this time, or in interstitial glucose concentrations during the remaining 23 h after exercise. Simulated games activity carries a lower risk of early, but not late-onset hypoglycemia than continuous running exercise in type 1 diabetes.
Objective: A lack of physical activity plays an important role in cardiovascular disease, however the mechanism(s) are poorly understood. In addition, the majority of studies which have examined the relationship between physical activity and arterial function have used subjective measures of activity. The aim of this cross-sectional study was to investigate if objectively measured physical activity is associated with arterial stiffness and wave reflection in patients attending an outpatient hypertension clinic. Design and Method: Physical activity was measured for 7 consecutive days using a triaxial accelerometer (RT3 Stayhealthy). This provides data on estimated energy expenditure in physical activity and time spent in the various intensities of activity. Brachial blood pressure (BP) was measured using an oscillometric technique (Omron) in the right arm. Using the same arm, augmentation index (AIx) and aortic BP were measured using radial applanation tonometry (SphygmoCor). Pulse wave velocity (PWV) was measured using the foot-to-foot method (Artech Medical). Results: Eighty adults (female, n = 40) with a mean ± sd age 49 ± 25y, body mass index (BMI) 29.7 ± 5.1 kg/m2 (n = 70) and waist circumference 101 ± 14 cm (n = 42) participated. PWV was 10.3 ± 2.4m/s (n = 36) and AIx was 27.1 ± 14.4% (n = 48). Physical activity data was available for n=53 patients. Time spent in at least moderate physical activity was 36 ± 31 minutes/d and n = 26 (49%) patients carried out at least 30 minutes/d of at least moderate intensity activity. AIx and aortic BP were significantly lower in those who engaged in higher amounts of vigorous activity (P < 0.01)(n = 48). In stepwise regression analysis, after adjusting for age, gender, BMI, alcohol intake and smoking, the only independent predictors of AIx were physical activity, heart rate and systolic BP. There was no relationship between physical activity and PWV (n = 36). Conclusion: Physical activity reduces aortic wave reflections and BP, independent of BP and age probably because of increased nitric oxide production in the medium sized arteries. This reiterates the importance of regular physical activity in hypertensive patients to maintain optimum wave reflections.
Background:
Aerobic exercise typically decreases blood glucose levels in individuals with type 1 diabetes. It is currently unknown if glucose responses to exercise and recovery differ between patients on multiple daily insulin injections (MDI) and continuous subcutaneous insulin infusion (CSII).
Subjects and methods:
Nineteen (16 male, three female) physically active individuals with type 1 diabetes took part in this observational study. Interstitial glucose levels (blinded) were compared during 45 min of standardized aerobic exercise (cycling or running at 60% peak aerobic capacity) and during 6 h of postexercise recovery between individuals using MDI (n=9) and CSII (n=10) therapy.
Results:
Both MDI and CSII groups had similar reductions in glucose levels during exercise, but responses in early and late recovery differed (group × time interaction, P<0.01). Participants using MDI had greater increases in glucose throughout recovery compared with individuals with CSII. Two-thirds of the MDI patients experienced late-onset post-exercise hyperglycemia (blood glucose >12 mmol/L) compared with only 1/10(th) of the CSII patients (P<0.01).
Conclusions:
Among individuals performing regular moderate-to-heavy intensity aerobic exercise, use of CSII helped to limit post-exercise hyperglycemia compared with MDI therapy and is not associated with increased risk for post-exercise late-onset hypoglycemia.
Individuals with Type 1 diabetes mellitus are susceptible to hypoglycaemia during and after continuous moderate-intensity exercise, but hyperglycaemia during intermittent high-intensity exercise. The combination of both forms of exercise may have a moderating effect on glycaemia in recovery. The aims of this study were to compare the physiological responses and associated glycaemic changes to continuous moderate-intensity exercise vs. continuous moderate-intensity exercise + intermittent high-intensity exercise in athletes with Type 1 diabetes.
Interstitial glucose levels were measured in a blinded fashion in 11 trained athletes with Type 1 diabetes during two sedentary days and during 2 days in which 45 min of afternoon continuous moderate-intensity exercise occurred either with or without intermittent high-intensity exercise. The total amount of work performed and the duration of exercise was identical between sessions.
During exercise, heart rate, respiratory exchange ratio, oxygen utilization, ventilation and blood lactate levels were higher during continuous moderate-intensity + intermittent high-intensity exercise vs. continuous moderate-intensity exercise (all P < 0.05). Despite these marked cardiorespiratory differences between trials, there was no difference in the reduction of interstitial glucose or plasma glucose levels between the exercise trials. Nocturnal glucose levels were higher in continuous moderate-intensity + intermittent high-intensity exercise and in sedentary vs. continuous moderate-intensity exercise (P < 0.05). Compared with continuous moderate-intensity exercise alone, continuous moderate-intensity + intermittent high-intensity exercise was associated with less post-exercise hypoglycaemia (5.2 vs. 1.5% of the time spent with glucose < 4.0 mmol/l) and more post-exercise hyperglycaemia (33.8 vs. 20.4% of time > 11.0 mmol/l).
Although the decreases in glucose level during continuous moderate-intensity exercise and continuous moderate-intensity + intermittent high-intensity exercise are similar, the latter form of exercise protects against nocturnal hypoglycaemia in athletes with Type 1 diabetes.
To determine the effects of 10 wk of resistance or aerobic exercise training on interleukin-6 (IL-6) and C-reactive protein (CRP). Further, to determine pretraining and posttraining associations between alterations of IL-6 and CRP and alterations of total body fat mass (TB-FM), intra-abdominal fat mass (IA-FM), and total body lean mass (TB-LM).
A sample of 102 sedentary subjects were assigned to a resistance group (n = 35), an aerobic group (n = 41), or a control group (n = 26). Before and after intervention, subjects were involved in dual-energy x-ray absorptiometry, muscular strength and aerobic fitness, measurements and further provided a resting fasted venous blood sample for measures of IL-6, CRP, cholesterol profile, triglycerides, glucose, insulin, and glycosylated hemoglobin. The resistance and the aerobic groups completed a respective 10-wk supervised and periodized training program, whereas the control group maintained sedentary lifestyle and dietary patterns.
Both exercise training programs did not reduce IL-6; however, the resistance and the aerobic groups reduced CRP by 32.8% (P < 0.05) and 16.1% (P = 0.06), respectively. At baseline, CRP was positively correlated with IL-6 (r = 0.35), (TB-FM) (r = 0.36), and IA-FM (r = 0.31) and was inversely correlated with aerobic fitness measures (all r values > or = -0.24). Compared with the resistance and the control groups, the aerobic group exhibited significant (P < 0.05) improvements in all aerobic fitness measures and significant reductions in IA-FM (7.4%) and body mass (1.1%). Compared with the aerobic and the control groups, the resistance group significantly (P < 0.05) improved TB-FM (3.7%) and upper (46.3%) and lower (56.6%) body strength.
Despite no alteration in baseline IL-6 and significantly smaller reductions in measures of adipose tissue as compared with the aerobic training group, only resistance exercise training resulted in significant attenuation of CRP concentration.
In this study adaptations in body composition, physical fitness and metabolic health were examined during 21 weeks of endurance and/or strength training in 39- to 64-year-old healthy women. Subjects (n = 62) were randomized into endurance training (E), strength training (S), combined strength and endurance training (SE), or control groups (C). S and E trained 2 and SE 2 + 2 times in a week. Muscle strength and maximal oxygen uptake (VO(2)max) were measured. Leg extension strength increased 9 +/- 8% in S (P < 0.001), 12 +/- 8% in SE (P < 0.001) and 3 +/- 4% in E (P = 0.036), and isometric bench press 20% only in both S and SE (P < 0.001). VO(2)max increased 23 +/- 18% in E and 16 +/- 12% in SE (both P < 0.001). The changes in the total body fat (dual X-ray absorptiometry) did not differ between groups, but significant decreases were observed in E (-5.9%, P = 0.022) and SE (-4.8%, P = 0.005). Lean mass of the legs increased 2.2-2.9% (P = 0.004-0.010) in S, SE and E. There were no differences between the groups in the changes in blood lipids, blood pressure or serum glucose and insulin. Total cholesterol and low-density lipoprotein cholesterol decreased and high-density lipoprotein cholesterol increased in E. Both S and SE showed small decreases in serum fasting insulin. Both endurance and strength training and their combination led to expected training-specific improvements in physical fitness, without interference in fitness or muscle mass development. All training methods led to increases in lean body mass, but decreases in body fat and modest improvements in metabolic risk factors were more evident with aerobic training than strength training.
We have investigated the relation between nocturnal insulin requirements and nocturnal growth hormone (GH) release in 26 diabetic adolescents at various puberty stages and have examined the effect of nocturnal GH suppression on pre-breakfast insulin requirement. In all the studies, euglycaemia was maintained overnight using a computer-calculated variable-rate insulin infusion, and 15-min blood samples were collected for GH assay. During initial clamp studies, insulin infusion rates were greater from 0500-0800 h (15.22 +/- 0.95 mU/kg/h, mean +/- SEM) than from 0100-0400 h (12.42 +/- 0.84 mU/kg/h, P less than 0.001). The increase in insulin infusion rate correlated with mean overnight GH concentration (r = 0.68, P less than 0.001), and was maximal at puberty stage 3 in both sexes. In seven of the subjects, a second identical clamp was performed following administration of 100 mg oral pirenzepine. During these studies, mean overnight GH levels were reduced by 11-85%, from 17.6 +/- 1.6 to 7.5 +/- 2.2 mU/l; P less than 0.01. Insulin requirements were not significantly different between the periods 0100-0400 and 0500-0800 h during these studies, and the reduction in pre-breakfast (0500-0800 h) insulin requirement when compared with the baseline studies correlated with the fall in GH secretion (rs = 0.82, P less than 0.01). The dawn increase in insulin requirement in adolescents with IDDM is related to the overnight GH secretion during puberty, and pre-breakfast insulin requirement can be reduced by suppressing nocturnal GH release.
The dawn phenomenon was evaluated in eight C-peptide-negative type I (insulin-dependent) diabetic patients on two occasions by measuring glucose concentrations every 30 min from 2400 to 0800 h while the subjects were receiving an insulin infusion (0.12 mU.kg-1.min-1). In random order at 2230 h, they orally received either a sleeping medication alone or with 5.0 mg methscopolamine bromide, an anticholinergic agent. The peak growth hormone (GH) concentrations (ng/ml +/- SE) after sleep were markedly inhibited by methscopolamine (4.7 +/- 2.6 vs. 23.0 +/- 9.2). During the control night, the late (0400-0800 h) glucose response (area under curve but above 0400 h value) was significantly higher (P less than .02) than the early (2400-0400 h) glucose response (area under curve but above 2400 h value). After methscopolamine, the early and late glucose responses were virtually identical. The anticholinergic agent did not affect glucagon levels, overnight urinary catecholamine excretion, or the diurnal cortisol concentrations. The total area under the free fatty acid (FFA) curves was significantly (P less than .05) reduced by methscopolamine. We conclude that sleep-induced GH secretion may cause the dawn phenomenon by increasing FFA levels. Oral administration of methscopolamine at bedtime is a simple pharmacological approach that could test the clinical importance of the dawn phenomenon.
During constant insulin infusion (0.15 mU X kg-1 X min-1) from 12 PM to 8 AM in 10 IDDM patients previously rendered euglycemic (Biostator), plasma glucose (5.4 +/- 0.2 mmol/L at 12 PM) increased by 3:30 AM and reached 12.1 +/- 1.6 mmol/L at 8 AM (P less than 0.001). Glucose production also increased at 3:30 AM; hyperglycemia, glucose utilization did not increase until after 5 AM. Plasma growth hormone (12 PM to 4 AM), cortisol (after 3:30 AM), noradrenaline (after 1:30 AM), and adrenaline (after 3:30 AM) but not glucagon increased significantly overnight, although plasma adrenaline and noradrenaline remained at subthreshold levels. Insulin clearance increased (approximately 25%, P less than 0.05) but only after 7 AM, resulting in a 4 mU/L decrease in plasma insulin. A significant correlation was found between increases in plasma glucose and increases in glucose production (r = 0.74, P less than 0.05) which in turn were significantly correlated with nocturnal peaks in plasma growth hormone (r = 0.66, P less than 0.05). From the sequence of events observed, we conclude that the Dawn Phenomenon in IDDM begins earlier than is currently thought (approximately 3:30 AM), that it is due to both accelerated glucose production and impaired glucose utilization, and that nocturnal increases in sympathetic nervous system activity and/or growth hormone secretion, but not changes in secretion of cortisol, adrenaline and glucagon or changes in insulin clearance, may be of pathogenetic importance.
The plasma norepinephrine (NE) and epinephrine (E) responses to a variety of stressors are influenced by age, adiposity, and exercise training status. The objectives of this study were to 1) compare basal levels as well as posture- and exercise-induced changes in plasma NE and E concentrations in young [25 +/- 1 (SE) yr; n = 24] and older (64 +/- 1 yr; n = 106) people and examine the associations of the responses with adiposity and maximal O2 uptake (VO2max) and 2) determine the extent to which the NE and E responses are altered by exercise training in older people. We found no significant differences in basal NE and E levels between young and older subjects. However, the NE response to standing was exaggerated in older people (696 +/- 39 vs. 512 +/- 61 pg/ml; P < 0.05), whereas NE and E responses to exercise requiring approximately 78% of VO2max were attenuated in older people (NE: 1,444 +/- 74 vs. 1,983 +/- 222 pg/ml; E: 109 +/- 10 vs. 228 +/- 29 pg/ml; both P < 0.01). Increments in NE and E during exercise were more closely associated with age (NE: r = -0.38; E: r = -0.46; both P < 0.05) and VO2max (NE: r = 0.43; E: r = 0.52; both P < 0.05) than with adiposity (NE: r = -0.29; E: r = -0.25; both P < 0.05). In 48 older subjects who completed 9 mo of exercise training, the increases in NE and E during exercise at the same absolute intensity were 39 and 57% lower, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
The purpose of this study was to compare age and gender effects of strength training (ST) on resting metabolic rate (RMR), energy expenditure of physical activity (EEPA), and body composition.
RMR and EEPA were measured before and after 24 wk of ST in 10 young men (20-30 yr), 9 young women (20-30 yr), 11 older men (65-75 yr), and 10 older women (65-75 yr).
When all subjects were pooled together, absolute RMR significantly increased by 7% (5928 +/- 1225 vs 6328 +/- 1336 kJ.d-1, P < 0.001). Furthermore, ST increased absolute RMR by 7% in both young (6302 +/- 1458 vs 6719 +/- 1617 kJ x d(-1), P < 0.01) and older (5614 +/- 916 vs 5999 +/- 973 kJ x d(-1), P < 0.05) subjects, with no significant interaction between the two age groups. In contrast, there was a significant gender x time interaction (P < 0.05) for absolute RMR with men increasing RMR by 9% (6645 +/- 1073 vs 7237 +/- 1150 kJ x d(-1), P < 0.001), whereas women showed no significant increase (5170 +/- 884 vs 5366 +/- 692 kJ x d(-1), P = 0.108). When RMR was adjusted for fat-free mass (FFM) using ANCOVA, with all subjects pooled together, there was still a significant increase in RMR with ST. Additionally, there was still a gender effect (P < 0.05) and no significant age effect (P = NS), with only the men still showing a significant elevation in RMR. Moreover, EEPA and TEE estimated with a Tritrac accelerometer and TEE estimated by the Stanford Seven-Day Physical Activity Recall Questionnaire did not change in response to ST for any group.
In conclusion, changes in absolute and relative RMR in response to ST are influenced by gender but not age. In contrast to what has been suggested previously, changes in body composition in response to ST are not due to changes in physical activity outside of training.
While the accepted measure of aerobic power remains the VO2max this test is extremely demanding even for athletes. There are serious practical and ethical concerns in attempting such testing in non-athletic or patient populations. An alternative method of measuring aerobic power in such populations is required. A limited body of work exists evaluating the accuracy of the Astrand-Ryhming nomogram and linear extrapolation of the heart rate/oxygen uptake plot. Issues exist in terms of both equipment employed and sample numbers.
Twenty-five normal subjects (mean age 28.6, range 22-50) completed 52 trials (Bruce treadmill protocol) meeting stringent criteria for VO2max performance. Respiratory gases were measured with a portable gas analyser on a five-sec sample period. The data was analysed to allow comparison of the reliability and validity of linear extrapolations to three estimates of heart rate maximum with the Astrand nomogram prediction.
Extrapolation was preferable yielding intraclass correlation co-efficients (ICC) of 0.9433 comparable to that of the observed VO2max at 0.9443 and a bias of -1.1 ml x min(-1) x kg(-1) representing a 2.19 percent underestimate.
This study provides empirical evidence that extrapolation of submaximal data can be employed with confidence for both clinical monitoring and research purposes. With the use of portable equipment and submaximal testing the scope for future research in numerous populations and non-laboratory environments is considerably increased.
To compare the response of blood glucose levels to intermittent high-intensity exercise (IHE) and moderate-intensity exercise (MOD) in individuals with type 1 diabetes.
Seven healthy individuals with type 1 diabetes were tested on two separate occasions, during which either a 30-min MOD or IHE protocol was performed. MOD consisted of continuous exercise at 40% Vo(2peak), while the IHE protocol involved a combination of continuous exercise at 40% Vo(2peak) interspersed with 4-s sprints performed every 2 min to simulate the activity patterns of team sports.
Both exercise protocols resulted in a decline in blood glucose levels. However, the decline was greater with MOD (-4.4 +/- 1.2 mmol/l) compared with IHE (-2.9 +/- 0.8 mmol/l; P < 0.05), despite the performance of a greater amount of total work with IHE (P < 0.05). During 60 min of recovery from exercise, glucose levels remained higher in IHE compared with MOD (P < 0.05). Furthermore, glucose levels remained stable during recovery from IHE, while they continued to decrease after MOD (P < 0.05). The stabilization of blood glucose levels with IHE was associated with elevated levels of lactate, catecholamines, and growth hormone during early recovery from exercise (P < 0.05). There were no differences in free insulin, glucagon, cortisol, or free fatty acids between MOD and IHE.
The decline in blood glucose levels is less with IHE compared with MOD during both exercise and recovery in individuals with type 1 diabetes.
Suppression of sleep-induced growth hormone secretion by anticholinergic agent abolishes dawn phenomenon
- MB Davidson
- MD Harris
- FH Ziel
- CS Rosenberg
Diabetes Canada Clinical Practice Guidelines Expert Committee.Physical activity and diabetes
- RJ Sigal
- MJ Armstrong
- SL Bacon
- NG Boule
- K Dasgupta
- GP Kenny
- MC Riddell
Diabetes Canada Clinical Practice Guidelines Expert Committee.Physical activity and diabetes
- R J Sigal
- M J Armstrong
- S L Bacon
- N G Boule
- K Dasgupta
- G P Kenny
- M C Riddell
Sigal RJ, Armstrong MJ, Bacon SL, Boule NG, Dasgupta K, Kenny
GP, Riddell MC; Diabetes Canada Clinical Practice Guidelines
Expert Committee.Physical activity and diabetes. Can J Diabetes.
2018;42(Suppl 1):S54-S63.
Similar magnitude of post-exercise hyperglycemia despite manipulating RE intensity in type 1 diabetes individuals
- D Turner
- BJ Gray
- S Luzio
- G Dunseath
- SC Bain
- S Hanley
- A Richards
- DC Rhydderch
- M Ayles
- LP Kilduff
- MD Campbell
- DJ West
- RM Bracken
Impact of single and multiple sets of RE in type 1 diabetes
- D Turner
- S Luzio
- BJ Gray
- G Dunseath
- ED Rees
- LP Kilduff
- MD Campbell
- DJ West
- SC Bain
- RM Bracken