Fat Oxidation Rates Are Higher During Running Compared With Cycling Over a Wide Range of Intensities
Abstract and Figures
The aim of the present study was to compare the intensity that elicits maximal fat oxidation (Fat(max)) determined using a cycle-ergometer and a treadmill-based protocol. Twelve moderately trained male subjects (66.9 +/- 1.8 mL. kg(-1). min(-1)) performed 2 graded exercise tests to exhaustion. One test was performed on a cycle ergometer while 1 test was performed on a motorized treadmill; stage duration during both trials was 3 minutes. Gas exchange measurements and heart rate (HR) recordings were performed throughout exercise. Fat oxidation rates were calculated using stoichiometric equations. Maximal fat oxidation rates were significantly higher during running compared with cycling (0.65 +/- 0.05 v 0.47 +/- 0.05 g. min(-1)). However, the intensity, which elicited maximal fat oxidation, was not significantly different between the cycle ergometer and treadmill test (62.1 +/- 3.1 v 59.2 +/- 2.8% Vo(2)max, respectively). Fat oxidation rates were significantly higher during the treadmill test compared with the cycle ergometer test from 55 to 80%Vo(2)max. Maximal oxygen uptake and maximal HR were significantly higher during the treadmill test. It was concluded that fat oxidation rates were higher during walking compared with cycling. Maximal fat oxidation was 28% higher when walking compared with cycling, but the intensity, which elicits maximal fat oxidation, is not different between these 2 exercise modes.
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... The higher VO 2 observed during running is in agreement with previous studies (Achten et al., 2003;Lafortuna et al., 2010). For example, among obese adolescents, Lafortuna et al. (2010) reported higher energy expenditure and oxygen uptake during running compared with cycling at a comparable HR. ...
Heart Rate (HR) is widely used for erobic exercise intensity prescriptions and/or studies of exercise training. It is often assumed that exercising at a given HR results in similar physiological response, regardless of exercise modality. This study aimed to gauge cellular immune mobilization to submaximal exercise at a given target HR on a cycle ergometer (CE) and treadmill (TM). Thirteen healthy male adults (23.2 ± 3.5 y.o) completed 4 laboratory visits. Participants performed two graded exercise tests to exhaustion on CE and TM and two 30‐min constant exercise challenges at 70% HR reserve on CE or TM in random order. Rating of Perceived Exertion (RPE) was recorded every 5 min, and blood was drawn before and after exercise to measure leukocytes subpopulation levels, lactate, and IL‐6. HR was successfully “clamped” during the exercise in CE and TM (CE 156.7 ± 1.1; TM 159.3 ± 1.6 bpm). Cycling was perceived as more strenuous than running and was accompanied by a greater increase in lactate post‐exercise (p < 0.0001; 6.2 ± 0.3 vs. 2.9 ± 0.3 mmol/L). IL‐6 and leukocytes subpopulations were significantly elevated post‐exercise (p < 0.003) with no difference between exercise modalities (monocytes; CE 57.6% TM 61.2%, granulocytes; CE 41.37%, TM 50.1%, lymphocytes; CE 91.03%, TM 78.8%). The findings revealed that HR is not sufficient in and of itself to fully assess the metabolic stress associated with a given exercise modality. However, despite different metabolic and subjective stress, the IL‐6 and leukocyte counts relative changes were similar in the two modalities.
... Previous cross-sectional studies consistently found that running was able to elicit a greater MFO than cycling. 27,29,73 This may be related to the amount and type of muscle primarily recruited by the different exercise modes. However, this potential mechanism is beyond the scope of our review, so we refer the interested reader to previous research on the effects of different exercise modes on fat oxidation. ...
Objective
to (1) systematically review the chronic effect of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on maximal fat oxidation (MFO) in overweight and obese adults, and (2) explore MFO influencing factors and its dose-response relationships with HIIT and MICT.
Methods
Studies using a between-group design involving overweight and obese adults and assessing the effect of HIIT and MICT on MFO were included. A meta-analysis on MFO indices was conducted, and the observed heterogeneities were explored through subgroup, regression, and sensitivity analyses.
Results
Thirteen studies of moderate to high quality with a total of 519 overweight and obese subjects were included in this meta-analysis (HIIT, n = 136; MICT, n = 235; Control, n = 148). HIIT displayed a statistically significant favorable effect on MFO compared to no-training (MD = 0.07; 95%CI [0.03 to 0.11]; I² = 0%). Likewise, MICT displayed a statistically significant favorable effect on MFO compared to no-training (MD = 0.10; 95%CI [0.06 to 0.15]; I² = 95%). Subgroup and regression analyses revealed that exercise intensity (Fatmax vs. non-Fatmax; %VO2peak), exercise mode, BMI, and VO2peak all significantly moderated MICT on MFO. When analyzing studies that have directly compared HIIT and MCIT in obese people, it seems there is no difference in the MFO change (MD = 0.01; 95%CI [-0.02 to 0.04]; I² = 64%). No publication bias was found in any of the above meta-analyses (Egger's test p > 0.05 for all).
Conclusion
Both HIIT and MICT are effective in improving MFO in overweight and obese adults, and they have similar effects. MCIT with an intensity of 65–70% VO2peak, performed 3 times per week for 60 min per session, will optimize MFO increases in overweight and obese adults. Given the lack of studies examining the effect of HIIT on MFO in overweight and obese adults and the great diversity in the training protocols in the existing studies, we were unable to make sound recommendations for training.
... g·min −1 ). This finding supports the data reported in healthy lean individuals [17,105,106], and demonstrates that exercising on a treadmill would require a lower training volume to achieve significant fat oxidation in comparison with stationary cycling. Interestingly, a previous systematic review reported that walking is the preferred exercise modality of individuals with obesity [107]. ...
Background Exercise training performed at maximal fat oxidation (FATmax) is an efficient non-pharmacological approach
for the management of obesity and its related cardio-metabolic disorders.
Objectives Therefore, this work aimed to provide exercise intensity guidelines and training volume recommendations for
maximizing fat oxidation in patients with obesity.
Methods A systematic review of original articles published in English, Spanish or French languages was carried out in
EBSCOhost, PubMed and Scopus by strictly following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement. Those studies that analyzed maximal fat oxidation (MFO) and FATmax in patients with obesity
(body fat > 25% for men; > 35% for women) by calculating substrate oxidation rates through indirect calorimetry during a
graded exercise test with short-duration stages (< 10 min) were selected for quantitative analysis. The accuracy of relative
oxygen uptake (% peak oxygen uptake [% ̇VO2peak]) and relative heart rate (% peak heart rate [%HRpeak]) for establishing
FATmax reference values was investigated by analyzing their intra-individual and inter-study variation. Moreover, cluster
analysis and meta-regression were used for determining the influence of biological factors and methodological procedures
on MFO and FATmax.
Results Sixty-four manuscripts were selected from 146 records; 23 studies only recruited men (n = 465), 14 studies only
evaluated women (n = 575), and 27 studies included individuals from both sexes (n = 6434). The majority of the evaluated
subjects were middle-aged adults (aged 40–60 y; 84%) with a poor cardiorespiratory fitness (≤ 43 mL·kg−1·min−1; 81%),
and the reported MFO ranged from 0.27 to 0.33 g·min−1. The relative heart rate at FATmax (coefficient of variation [CV]:
8.8%) showed a lower intra-individual variation compared with relative oxygen uptake (CV: 17.2%). Furthermore, blood
lactate levels at FATmax ranged from 1.3 to 2.7 mmol·L−1 while the speed and power output at FATmax fluctuated from 4 to
5.1 km·h−1 and 42.8–60.2 watts, respectively. Age, body mass index, cardiorespiratory fitness, FATmax, the type of ergometer
and the stoichiometric equation used to calculate the MFO independently explained MFO values (R2 = 0.85; p < 0.01). The
MFO in adolescents was superior in comparison with MFO observed in young and middle-aged adults. On the other hand,
the MFO was higher during treadmill walking in comparison with stationary cycling. Body fat and MFO alone determined
29% of the variation in FATmax (p < 0.01), noting that individuals with body fat > 35% showed a heart rate of 61–66%
HRpeak
while individuals with < 35% body fat showed a heart rate between 57 and 64% HRpeak.
Neither biological sex nor
the analytical procedure for computing the fat oxidation kinetics were associated with MFO and FATmax.
Conclusion Relative heart rate rather than relative oxygen uptake should be used for establishing FATmax reference values
in patients with obesity. A heart rate of 61–66% HRpeak
should be recommended to patients with > 35% body fat while a
heart rate of 57–64% HRpeak
should be recommended to patients with body fat < 35%. Moreover, training volume must be
higher in adults to achieve a similar fat oxidation compared with adolescents whereas exercising on a treadmill requires a
lower training volume to achieve significant fat oxidation in comparison with stationary cycling.
... In this sense, some tests carried out on the elliptical and treadmill have not found significant differences in the values reached for maximum oxygen consumption in trained men and women (Dalleck, 2004). On the other hand, in previous investigations in which other machines such as the bicycle are analysed, they have determined differences in terms of fat oxidation with respect to other modalities and their active muscle mass (Achten et al., 2003). In relation to the elliptical and the treadmill, the various effects produced with respect to body composition, HR and maximum oxygen consumption have been observed, obtaining similar improvements (Mercer et al., 2001;Donne & Egana, 2004). ...
The objective of this article was to compare different cardiovascular training machines and their effects on the body, as well as to determine their suitability for people with low intensity or high intensity training needs. A total of 8 physically active and healthy male subjects (mean ± standard deviation; age: 28.45 ± 1.75 years; height: 1.84 ± 0.07 m; body weight 76.42 ± 8.62 kg; body mass index: 25.5 ± 2.6) were evaluated through of an incremental exercise test at different intensities on two different machines: Elliptical Domyos 680 (BED) and Deconstruct Elliptical 331-EF (DEC). To compare both machines against the two mentioned training needs, two different protocols were carried out: Low Intensity Protocol (LIP) and High Intensity Protocol (HIP). In addition, a thermographic analysis was carried out in order to determine the temperature differences reached in the musculature. No significant differences were found in HR and EE (p < .05) between the two machines. However, a greater and more progressive activation of the muscles of the upper extremities was observed in the DEC machine. In the HIP, HR and EE were measured, obtaining significant differences (p < .05) higher in the DEC machine. Therefore, in our comparison, the Deconstruct Elliptical machine produced more appropriate results for both low and high intensity training compared to the Elliptical machine. These results and the novel nature of the Deconstruct Elliptical raise the need for further studies to better understand this machine.
... Many authors have modified this protocol, varying the starting load and the magnitude of the increments to adapt it to diverse populations and different levels of training. In addition, it has been described with different kinds of exercise, e.g., cycle ergometer [54], treadmill [55], or arm cycle ergometer [56]. This has made it possible to establish reference values for PFO and Fatmax according to the level of training and the type of exercise performed. ...
Background:
The aim of this study was to summarize evidence on energy metabolism through peak fat oxidation (PFO) and maximum fat oxidation (Fatmax), as well as to analyze the protocols used in people with spinal cord injury (SCI) and to examine the main factors related to fat oxidation ability (i.e., age, sex, level of physical activity, and level and degree of injury).
Methods:
Studies to determine PFO and Fatmax using indirect calorimetry with an arm exercise protocol for SCI patients were included after a systematic search. Other endpoints included study design, sample size, control group, demographic data, level of injury, physical condition, protocol, outcomes measured, and statistical findings.
Results:
Eight studies (n = 560) were included. The mean value of VO2peak was 1.86 L∙min-1 (range 0.75-2.60 L∙min-1) (lowest value in the tetraplegic subjects). The PFO ranged between 0.06 and 0.30 g∙min-1 (lowest rates: the non-trained subjects with cervical SCI; highest: the tetraplegic subjects). Two types of exercise protocol were found: arm cycle ergometer, and wheelchair propulsion with a computerized ergometer. Five studies used an incremental protocol (2-3 min/stage, different load increments); the rest performed tests of 20 min/stage at three intensities.
Conclusion:
There are few existing studies measuring fat oxidation in SCI, many of which used small and heterogeneous samples. PFO was lower in SCI subjects when compared with non-injured people performing lower-limb exercise; however, comparing upper-limb exercise, people with SCI showed higher values.
Introduction: Metabolic syndrome (MetS) is an endocrinopathy with a combination of cardiovascular and metabolic compounds. In our study, it is expected to obtain results showing that mortality rate, loss of workforce, and treatment costs due to disorders caused by MetS can be reduced by physical exercise. The study analyses the effect of moderate exercise training on this Apolipoprotein E (ApoE), Apolipoprotein CIII (ApoCIII), adiponectin, resistin, interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) which are thought to have a role in the deterioration of glucose and lipid metabolism in MetS.
Methods: This clinical experimental study consists of 3 groups. The MetS+E (n=24) group, which included the participants who agreed to participate in the exercise program in addition to their medical treatment, the MetS (n=23) group who received medical treatment but did not exercise, and the Control+E (n=25) group, which included healthy volunteers who had the same protocol as MetS+E ApoE, ApoCIII, adiponectin, resistin, IL-6, and TNF-α plasma levels of all participants were measured both at the beginning of the study and at the end of the protocol.
Results: At the end of the study we reached the following findings; insulin and Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) levels decreased in exercise groups (p=0,03). ApoCIII levels increased in all the groups after the study (p<0,01). IL-6 levels decreased in MetS+E (p<0,01) and Control+E (p=0,037). ApoE (p=0,01) and TNF-α (p=0,037) levels decreased only in the Control+E group.
Conclusion: Training showed metabolic, anti-inflammatory, and physical improvements independent of ApoE and ApoCIII in those with MetS.
Introduction: Metabolic syndrome (MetS) is an endocrinopathy with a combination of cardiovascular and metabolic compounds. In our study, it is expected to obtain results showing that mortality rate, loss of workforce, and treatment costs due to disorders caused by MetS can be reduced by physical exercise. The study analyses the effect of moderate exercise training on this Apolipoprotein E (ApoE), Apolipoprotein CIII (ApoCIII), adiponectin, resistin, interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) which are thought to have a role in the deterioration of glucose and lipid metabolism in MetS. Methods: This clinical experimental study consists of 3 groups. The MetS+E (n=24) group, which included the participants who agreed to participate in the exercise program in addition to their medical treatment, the MetS (n=23) group who received medical treatment but did not exercise, and the Control+E (n=25) group, which included healthy volunteers who had the same protocol as MetS+E ApoE, ApoCIII, adiponectin, resistin, IL-6, and TNF-α plasma levels of all participants were measured both at the beginning of the study and at the end of the protocol. Results: At the end of the study we reached the following findings; insulin and Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) levels decreased in exercise groups (p=0,03). ApoCIII levels increased in all the groups after the study (p<0,01). IL-6 levels decreased in MetS+E (p<0,01) and Control+E (p=0,037). ApoE (p=0,01) and TNF-α (p=0,037) levels decreased only in the Control+E group. Conclusion: Training showed metabolic, anti-inflammatory, and physical improvements independent of ApoE and ApoCIII in those with MetS.
Background/Objectives: A weekly combination of a high volume of moderate-intensity continuous training (MICT) with a low volume of high-intensity interval training (HIIT) provides important improvements in body composition and physical capacities in individuals with obesity. However, previous studies did not determine the weekly proportions of HIIT and MICT a priori. This study aimed to investigate changes in body composition, physical capacities and the fat oxidation rate in obese male adults by comparing a combination of MICT and HIIT, called combined training (COMB), with HIIT for a 12-week period.
Methods: Thirty-four obese male adults (mean age: 39.4±7.0 y; mean body mass index [BMI] 34.0±4.2 kg∙m−2) participated in this study (n = 18 for COMB, n = 16 HIIT), attending ~ 36 training sessions. The COMB group performed 3 repetitions of 2 min at 95% of peak oxygen uptake (V’O2 peak) (e.g., HIIT ≤20%), followed by 30 min at 60% of VO2 peak (e.g., MICT ≥80%). The HIIT group performed 5–7 repetitions of 2 min at 95% of VO2 peak. At baseline (PRE) and at the end of the training period (POST), body composition, VO2 peak, and the fat oxidation rate were measured. The two training programs were equivalent in caloric expenditure.
Results: At POST, body mass (BM) and fat mass (FM) decreased by a mean of 3.09±3.21 kg and 3.90±2.40 kg, respectively (P<0.05), in both groups and V’O2 peak increased in both groups by a mean of 0.47±0.34 L min-1 (P< 0.05). The maximal fat oxidation rate increased similarly in both groups from 0.32±0.05 to 0.36±0.06 g min-1 (P < 0.05).
Conclusion: COMB training represents a viable alternative to HIIT to improve anthropometric characteristics, physical capacities and fat oxidation in obese male adults.
In general, the concept of a mechanism in biology has three distinct meanings. It may refer to a philosophical thesis about the nature of life and biology, to the internal workings of a machine-like structure, or to the causal explanation of a particular phenomenon [1].
Understanding the biological mechanisms that justify acute and chronic physiological responses to exercise interventions determines the development of training principles and training methods. A strong understanding of the effects of exercise in humans may help
researchers to identify what causes specific biological changes and to properly identify the
most adequate processes for implementing a training stimulus [1].
Despite the significant body of knowledge regarding the physiological and physical effects of different training methods (based on load dimensions), some biological causes of those changes are still unknown. Additionally, few studies have focused on natural biological variability in humans and how specific human properties may underlie different responses to the same training intervention. Thus, more original research is needed to
provide plausible biological mechanisms that may explain the physiological and physical effects of exercise and training in humans.
In this Special Issue, we discuss/demonstrate the biological mechanisms that underlie the beneficial effects of physical fitness and sports performance, as well as their importance and their role in/influences on physical health.
A total of 28 manuscripts are published here, of which 25 are original articles, two are reviews, and one is a systematic review.
Two papers are on neuromuscular training programs (NMTs), training monotony (TM), and training strain (TS) in soccer players [2,3]; five articles provide innovative findings about testosterone and cortisol [4,5], gastrointestinal hormones [6], spirulina [7], and concentrations of erythroferrone (ERFE) [8]; another five papers analyze fitness and
its association with other variables [7,9–12]; three papers examine body composition in elite female soccer players [2], adolescents [6], and obese women [7]; five articles examines the effects of high-intensity interval training (HIIT) [7,10,13–15]; one paper examines the
acute effects of different levels of hypoxia on maximal strength, muscular endurance, and cognitive function [16]; another article evaluates the efficiency of using vibrating exercise equipment (VEE) compared with using sham-VEE in women with CLBP (chronic lowback pain) [17]; one article compares the effects of different exercise modes on autonomic modulation in patients with T2D (type 2 diabetes mellitus) [14]; and another paper analyzes the changes in ABB (acid–base balance) in the capillaries of kickboxers [18]. Other studies evaluate: the effects of resistance training on oxidative stress and muscle damage in spinal cord-injured rats [19]; the effects of muscle training on core muscle performance in rhythmic
gymnasts [20]; the physiological profiles of road cyclist in different age categories [21]; changes in body composition during the COVID-19 [22]; a mathematical model capable of predicting 2000 m rowing performance using a maximum-effort 100 m indoor rowing
ergometer [23]; the effects of ibuprofen on performance and oxidative stress [24]; the associations of vitamin D levels with various motor performance tests [12]; the level of knowledge on FM (Fibromyalgia) [25]; and the ability of a specific BIVA (bioelectrical
impedance vector analysis) to identify changes in fat mass after a 16-week lifestyle program in former athletes [26]. Finally, one review evaluates evidence from published systematic reviews and meta-analyses about the efficacy of exercise on depressive symptoms in cancer patients [27]; another review presents the current state of knowledge on satellite cell dependent skeletal muscle regeneration [28]; and a systematic review evaluates the effects of exercise on depressive symptoms among women during the postpartum period [29]
The effects of carbohydrate or water ingestion on metabolism were investigated in seven male subjects during two running and two cycling trials lasting 60 min at individual lactate threshold using indirect calorimetry, U- ¹⁴ C-labeled tracer-derived measures of the rates of oxidation of plasma glucose, and direct determination of mixed muscle glycogen content from the vastus lateralis before and after exercise. Subjects ingested 8 ml/kg body mass of either a 6.4% carbohydrate-electrolyte solution (CHO) or water 10 min before exercise and an additional 2 ml/kg body mass of the same fluid after 20 and 40 min of exercise. Plasma glucose oxidation was greater with CHO than with water during both running (65 ± 20 vs. 42 ± 16 g/h; P < 0.01) and cycling (57 ± 16 vs. 35 ± 12 g/h; P < 0.01). Accordingly, the contribution from plasma glucose oxidation to total carbohydrate oxidation was greater during both running (33 ± 4 vs. 23 ± 3%; P < 0.01) and cycling (36 ± 5 vs. 22 ± 3%; P < 0.01) with CHO ingestion. However, muscle glycogen utilization was not reduced by the ingestion of CHO compared with water during either running (112 ± 32 vs. 141 ± 34 mmol/kg dry mass) or cycling (227 ± 36 vs. 216 ± 39 mmol/kg dry mass). We conclude that, compared with water, 1) the ingestion of carbohydrate during running and cycling enhanced the contribution of plasma glucose oxidation to total carbohydrate oxidation but 2) did not attenuate mixed muscle glycogen utilization during 1 h of continuous submaximal exercise at individual lactate threshold.
The influence of exercise mode and 6% carbohydrate (C) vs. placebo (P) beverage ingestion on granulocyte and monocyte phagocytosis and oxidative burst activity (GMPOB) after prolonged and intensive exertion was measured in 10 triathletes. The triathletes acted as their own controls and ran or cycled for 2.5 h at approximately 75% maximal O2 uptake, ingesting C or P (4 total sessions, random order, with beverages administered in double-blind fashion). During the 2. 5-h exercise bouts, C or P (4 ml/kg) was ingested every 15 min. Five blood samples were collected (15 min before exercise, immediately after exercise, and 1.5, 3, and 6 h after exercise). The pattern of change over time for GMPOB was significantly different between C and P conditions (P </= 0.05), with postexercise values lower during the C trials. Little difference was measured between running and cycling modes. C relative to P ingestion (but not exercise mode) was associated with higher plasma levels of glucose and insulin, lower plasma levels of cortisol and growth hormone, and lower blood neutrophil and monocyte cell counts. These data indicate that C vs. P ingestion is associated with higher plasma glucose levels, an attenuated cortisol response, and lower GMPOB.
Carbohydrate (CHO) ingestion during exercise, in the form of CHO-electrolyte beverages, leads to performance benefits during prolonged submaximal and variable intensity exercise. However, the mechanism underlying this ergogenic effect is less clear. Euglycaemia and oxidation of blood glucose at high rates late in exercise and a decreased rate of muscle glycogen utilisation (i.e. glycogen ‘sparing’) have been proposed as possible mechanisms underlying the ergogenic effect of CHO ingestion. The prevalence of one or the other mechanism depends on factors such as the type and intensity of exercise, amount, type and timing of CHO ingestion, and pre-exercise nutritional and training status of study participants. The type and intensity of exercise and the effect of these on blood glucose, plasma insulin and catecholamine levels, may play a major role in determining the rate of muscle glycogen utilisation when CHO is ingested during exercise. The ingestion of CHO (except fructose) at a rate of >45 g/h, accompanied by a significant increase in plasma insulin levels, could lead to decreased muscle glycogen utilisation (particularly in type I fibres) during exercise. Endurance training and alterations in pre-exercise muscle glycogen levels do not seem to affect exogenous glucose oxidation during submaximal exercise. Thus, at least during low intensity or intermittent exercise, CHO ingestion could result in reduced muscle glycogen utilisation in well trained individuals with high resting muscle glycogen levels. Further research needs to concentrate on factors that regulate glucose uptake and energy metabolism in different types of muscle fibres during exercise with and without CHO ingestion.
Ventilation and acid-base responses were studied at comparable levels of O2 uptake during cycle ergometer and treadmill exercise, to determine the extent to which the type of exercise affects these responses. Twenty male subjects performed 50-, 100-, and 150-W cycle ergometer exercise and three work rates of similar O2 uptake on a treadmill. At comparable oxygen uptakes, arterial lactate and VE were higher and arterial pH and bicarbonate were lower for cycle ergometer than treadmill exercise. These differences could be accounted for by the greater degree of metabolic acidosis during cycle ergometer work. The increment in VE over that predicted (from an extrapolation of the linear relationship of the VE-VO2 relationship for low work rates) was linearly related to the decrease in arterial bicarbonate; VE was increased by approximately 4 1/min for each meq/1 of bicarbonate decrease for both treadmill and cycle ergometry.
The purpose of this study was to compare gastric emptying (GE) responses during intense, prolonged cycling and running. It is important to discern whether gastric emptying (GE) responses are exercise-mode specific, since the findings of cycling and running studies are often compared and applied to one another. Ten male biathletes cycled (CY) and ran (R) for 1 h at 75% of their mode-specific VO2max or rested (S) and consumed water (SW, CYW, RW) or a 7% carbohydrate solution (SC, CYC, RC) at a rate of 10 ml.kg-1.h-1 (approximately 180 ml at 0, 15, 30, and 45 min). No differences were found between CYW, CYC, RW, RC, and SC for volume of drink emptied (mean +/- SE) (522.8 +/- 47.9 ml) and GE rate (range, 8.2 +/- 0.9 (RC) to 9.3 +/- 0.6 ml.min-1 (SC]. A mean of 72.7 +/- 5.7% of the total consumed volume was emptied. The GE rate during SW was significantly (P less than 0.05) greater than the other conditions (11.3 +/- 0.4 ml.min-1, 94.0 +/- 1.9% of total consumed volume emptied). Substantial volumes of water and a 7% carbohydrate solution are thus emptied from the stomach during prolonged, intense running and cycling, with no differences in GE between these exercise modes. These data suggest that recommendations concerning GE are reciprocal between running and cycling bouts similar to those in the current study.
The purpose of this study was to investigate the role of exercise intensity on the post-exercise thermogenic effect (PETE), with or without feeding, in five lean (less than 15 percent body fat) and five borderline obese (between 20 and 25 percent body fat) individuals when the total caloric expenditure during exercise was equated to 720 kcal by adjusting exercise duration. Each subject participated in six testing sessions, including the measurement of resting metabolic rate (RMR), dietary induced thermogenesis (DIT) following a 720 kcal liquid meal, and four exercise trials including: (1) exercising on a treadmill at both 30 percent and 60 percent of VO2 max followed by a 720 kcal liquid meal (30F and 60F); and (2) exercising on a treadmill at both 30 percent and 60 percent of VO2 max followed by a non-caloric liquid meal substitute (water) matched by volume to the caloric liquid meal (30NF and 60NF). Indirect calorimetry was used to determine metabolic rate prior to each treatment (0-30 min RMR) and at 0-30, 50-60, 80-90, 110-120, 140-150, and 170-180 min following the feeding, exercise only, or exercise and feeding treatments. A significant difference in the post-exercise oxygen consumption was found between the two calorically equated exercise bouts (720 kcal) at 30 percent and 60 percent of each subject's VO2 max without feeding when all measurement periods following exercise were averaged together (60NF = 13.5 percent increase and 30NF = 5.5 percent). This difference was observed in both the lean and borderline obese subjects, with no significant difference between the two groups. In addition, when walking at either 30 percent or 60 percent of VO2 max preceded feeding, a significant attenuation in the rise of post-feeding RER values was observed in both groups with the higher exercise intensity showing the greatest RER attenuation when compared to the DIT trial. These results suggest that exercise intensity may play a significant role independent of the total energy expenditure in potentiating a person's post-exercise oxygen consumption rate and post-exercise substrate utilization for periods of up to 180 mins.
The purpose of this study was to examine differences in muscle glycogen storage during three successive days of running or cycling. In a crossover design, seven male subjects performed two 3-d trials of either running (trial R) or cycling (trial C) for 60 min at 75% VO2max. Biopsy samples were obtained before and after each day's exercise from the gastrocnemius (trial R) or vastus lateralis (trial C) muscle. Diets in the 2 d preceding and during each trial contained 5 g carbohydrate.kg-1.d-1 and 14,475 +/- 402 kJ.d-1. Mean pre-exercise glycogen content (mmol.kg-1 wet wt.) was significantly reduced in both trials on day 3 (103.4 +/- 6.0) when compared to day 1 and day 2 (119.9 +/- 6.8 and 116.4 +/- 5.7, respectively). Day 1 glycogen reduction was significantly greater in trial C (P less than 0.03), and glycogen restorage was greater (P less than 0.02) only in trial C between the 1st and 2nd d. On day 3, spectrophotometric analysis of PAS strains showed that pre-exercise glycogen content in either muscle group was significantly (P less than 0.01) less in Type I as compared to Type II fibers. This difference in fiber glycogen storage did not appear to be attributable to muscle damage as negligible leukocyte infiltration and low blood CK levels were obtained. No difference between modes were observed for CK values throughout the trials. These data suggest that the depressed glycogen storage before the 3rd d of exercise was due to the moderate carbohydrate intake.
The purpose of this study was to compare energy expenditure and substrate utilization during 60 min of steady state-exercise at similar heart rates (HR) using four exercise modes: stationary cycle (C), rower (R), ski simulator (S), and treadmill (walking) (T). Five subjects (means age = 23 +/- 4 yr) performed 60 min of continuous exercise at 65% HR max on each of the four modes in random order. Total energy (TE) and fat energy (FE) expenditure were determined from VO2 and respiratory exchange ratio (RER). VO2 during exercise averaged 2.427 for C, 2.167 for R, 2.242 for S, and 2.420 l min-1 for T and were not significantly different by repeated measures ANOVO (p greater than 0.05). RER, TE, and FE also were not statistically different among exercise modes. However, walking and skiing tended to use more fat; the average 60 min cumulative exercise values were 960 for C, 871 for R, 1088 for S, and 1188 kJ for T. The rate of fat expenditure generally increased after 20 min on all modes. These results indicate that the energy expended at comparable relative HR's is similar for four aerobic exercise modes.
The purpose of this study was to determine whether the postponement of fatigue in subjects fed carbohydrate during prolonged strenuous exercise is associated with a slowing of muscle glycogen depletion. Seven endurance-trained cyclists exercised at 71 +/- 1% of maximal O2 consumption (VO2max), to fatigue, while ingesting a flavored water solution (i.e., placebo) during one trial and while ingesting a glucose polymer solution (i.e., 2.0 g/kg at 20 min and 0.4 g/kg every 20 min thereafter) during another trial. Fatigue during the placebo trial occurred after 3.02 +/- 0.19 h of exercise and was preceded by a decline (P less than 0.01) in plasma glucose to 2.5 +/- 0.5 mM and by a decline in the respiratory exchange ratio (i.e., R; from 0.85 to 0.80; P less than 0.05). Glycogen within the vastus lateralis muscle declined at an average rate of 51.5 +/- 5.4 mmol glucosyl units (GU) X kg-1 X h-1 during the first 2 h of exercise and at a slower rate (P less than 0.01) of 23.0 +/- 14.3 mmol GU X kg-1 X h-1 during the third and final hour. When fed carbohydrate, which maintained plasma glucose concentration (4.2-5.2 mM), the subjects exercised for an additional hour before fatiguing (4.02 +/- 0.33 h; P less than 0.01) and maintained their initial R (i.e., 0.86) and rate of carbohydrate oxidation throughout exercise. The pattern of muscle glycogen utilization, however, was not different during the first 3 h of exercise with the placebo or the carbohydrate feedings. The additional hour of exercise performed when fed carbohydrate was accomplished with little reliance on muscle glycogen (i.e., 5 mmol GU X kg-1 X h-1; NS) and without compromising carbohydrate oxidation. We conclude that when they are fed carbohydrate, highly trained endurance athletes are capable of oxidizing carbohydrate at relatively high rates from sources other than muscle glycogen during the latter stages of prolonged strenuous exercise and that this postpones fatigue.
Eight well-trained male cyclists were used to determine the influence of carbohydrate feedings on exercise performance and muscle glycogen use. Two days prior to each trial, the subjects performed a 60-min "depletion ride" at 70% VO2max, which was followed by the ingestion of a high carbohydrate diet (approximately 500 g X -1). During the experimental trials, the men performed 2 h of cycling exercise and consumed 150 ml of 1 of 4 solutions at 24-min intervals. The drinks were: H2O (artificially flavored and sweetened); maltodextrin (5 g X 100 ml-1) and fructose (5 g X 100 ml-1); maltodextrin (7.7 g X 100 ml-1) and high fructose corn syrup (2.3 g X 100 ml-1); maltodextrin (3 g X 100 ml-1 and glucose (2 g X 100 ml-1). The amount of work completed during the four trials was not significantly different. Initial glycogen levels were high, and glycogen values were not significantly different at the beginning of exercise or at 90 min (185.35 +/- 3.26 and 91.93 +/- 3.39, respectively). Blood glucose was greater at 60 min in trial maltodextrin and glucose (5.70 +/- 0.36 mmoles X l-1), maltodextrin and high fructose corn syrup (6.05 +/- 0.54), and maltodextrin and fructose (6.03 +/- 0.42) compared to H2O (4.97 +/- 0.35) (P less than 0.05). Blood glucose remained elevated at 90 min during the maltodextrin and fructose and maltodextrin and high fructose corn syrup trials and at 120 min in the maltodextrin and fructose trial. No differences were observed between trials in blood lactate, serum glycerol, respiratory exchange ratio, or the subjects' perception of effort.(ABSTRACT TRUNCATED AT 250 WORDS)