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Exercise-induced muscle damage: Effect on circulating leukocyte and lymphocyte subsets

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Francis X Pizza at University of Toledo
Francis X Pizza
Joel B Mitchell at Texas Christian University
Joel B Mitchell
Bruce H Davis at Trillium Diagnostics, LLC
Bruce H Davis
  • Trillium Diagnostics, LLC
RAYMOND D. STARLING
RAYMOND D. STARLING
RAYMOND D. STARLING
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Abstract

The purpose of this study was to determine the effect of downhill and level running on circulating leukocyte and lymphocyte subsets and T lymphocyte activation. Using a random cross-over design, 10 runners completed two trials of 60 min of level running (0% grade; LR) and downhill running (-10% grade; DHR) at 70% of level VO2max. Blood samples were obtained preexercise and immediately postexercise (POST) and at 1.5, 12, 24, and 48 h of recovery. Creatine kinase activity peaked at 12 h of recovery from DHR and was not significantly altered following LR. The number of total T, CD16+, CD3+CD56+ cells were significantly higher POST DHR compared with LR. Leukocyte and neutrophil counts were significantly higher at 1.5 and 12 h of recovery from DHR compared with LR. The number of activated CD8+ cells (CD25+ CD8+) was significantly higher at 12 h of DHR compared to LR. Total T cells were significantly reduced at various time points during the 48 h of recovery from LR and DHR. In summary, DHR relative to LR resulted in a greater mobilization of lymphocytes (post), neutrophils (1.5-12 h of recovery) and activation of CD8+ cells at 12 h of recovery. In addition, reductions in circulating T lymphocyte subsets occurred following both conditions.
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... The findings of our study show an increase in the frequency of CD3 − /CD56 + NK cells among lymphocytes due to our exercise protocol. This result is in line with earlier findings [26,27]. The same exercise-induced increase in frequency could be observed both in the case of CD3 − /CD56 bright+ and CD3 − /CD56 dim+ NK cells. ...
... The percentage of CD3 + T cells among lymphocytes showed a decrease due to our exercise protocol. That is again in line with the earlier findings of Pizza et al. [27]. ...
... DOMS could alter this homeostasis by significantly increasing the percentage of NKT-like cells; however, in some cases, it decreased their ratio among lymphocytes. It must be noted that Pizza et al. showed earlier that downhill running significantly increased the total number of NKT-like cells post-exercise in contrast to level running [27]. ...
CD3 + /CD56 + NKT-like Cells Show Imbalanced Control Immediately after Exercise in Delayed-Onset Muscle Soreness
Article
Full-text available
  • Sep 2022
  • INT J MOL SCI
The purpose of the study was to carry out an immunophenotypical characterization with a special focus on natural killer cells of junior swimmers from the Hungarian National Swim Team before and after an intensive acute exercise. Nineteen swimmers, ten females and nine males, completed the exercise protocol. Sixteen swimmers experienced delayed-onset muscle soreness. Most of our findings substantiated earlier results, such as the increase in the percentage of the CD3 − /CD56 + natural killer cells and the CD3 − /CD56 dim+ NK cells, and the decrease in the percentage of CD3 + T cells among lymphocytes after the exercise protocol. The drop of natural killer cell activity back to the pre-exercise level was in line with earlier findings. Interestingly, the percentage of CD3 + /CD56 + NKT-like cells did not change significantly in those three swimmers who did not report delayed-onset muscle soreness. On the contrary, the percentage of CD3 + /CD56 + NKT-like cells among lym-phocytes increased in fourteen and decreased in two swimmers reporting delayed-onset muscle soreness. This study for the first time demonstrated a link between the delayed-onset muscle sore-ness and the imbalanced control of CD3 + /CD56 + NKT-like cells among lymphocytes. However, validation of this association in a larger sample size study will be necessary.
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... In young healthy women, a 30 min treadmill run increased circulating CD3 + CD56 + NKT-like cell numbers by 3-fourfold, before returning to pre-exercise levels one hour later (Zelazowska et al. 1997). In young healthy men, 60 min of treadmill running elicited a similar response for CD3 + CD56 + NKT-like cells (Pizza et al. 1995). Vigorous cycling for 84 min increased CD3 + CD16 + CD56 + NKT-like cells by 84% (Gabriel et al. 1992) while 60 min of cycling elicited 2-threefold increases in CD3 + CD56 + NKT-like cells in young men (Timmons et al. 2004). ...
... In fact, NKTlike cells may be less responsive to catecholamines than NK cells, and thus preferentially respond to alternative exercise responses (Søndergaard et al. 1999). For example, muscle damage from downhill running induces greater mobilization of CD3 + CD56 + NKT-like cells into the blood compared to a level gradient (Pizza et al. 1995). Elevated NKT-like cell number (as well as NK cells, CD8 + , and CD4 + T cells) in the blood following damage-inducing exercise is suggestive of a rapid stress/damage immune response requiring specialized effector cells (Pizza et al. 1995). ...
... For example, muscle damage from downhill running induces greater mobilization of CD3 + CD56 + NKT-like cells into the blood compared to a level gradient (Pizza et al. 1995). Elevated NKT-like cell number (as well as NK cells, CD8 + , and CD4 + T cells) in the blood following damage-inducing exercise is suggestive of a rapid stress/damage immune response requiring specialized effector cells (Pizza et al. 1995). This is consistent with the involvement of NKT cells, specifically iNKT cells, in sterile inflammation responses, such as tissue injury (Ferhat et al. 2018). ...
Does exercise attenuate age- and disease-associated dysfunction in unconventional T cells? Shining a light on overlooked cells in exercise immunology
Article
Full-text available
  • Apr 2021
  • EUR J APPL PHYSIOL
Unconventional T Cells (UTCs) are a unique population of immune cells that links innate and adaptive immunity. Following activation, UTCs contribute to a host of immunological activities, rapidly responding to microbial and viral infections and playing key roles in tumor suppression. Aging and chronic disease both have been shown to adversely affect UTC numbers and function, with increased inflammation, change in body composition, and physical inactivity potentially contributing to the decline. One possibility to augment circulating UTCs is through increased physical activity. Acute exercise is a potent stimulus leading to the mobilization of immune cells while the benefits of exercise training may include anti-inflammatory effects, reductions in fat mass, and improved fitness. We provide an overview of age-related changes in UTCs, along with chronic diseases that are associated with altered UTC number and function. We summarize how UTCs respond to acute exercise and exercise training and discuss potential mechanisms that may lead to improved frequency and function.
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... It is unlikely that IL-6 released by muscle cells during exercise [85] explains the difference between the intensities of exercise protocols. It is known that IL-6 attracts lymphocytes to the circulation together with β-adrenergic signalling during exercise [67]; however, there is a higher release of IL-6 within exercise protocols with higher energetic demand, such as the higher volume and during regimens [85][86][87], which do not agree with our findings. ...
... It is unlikely that IL-6 released by muscle cells during exercise [85] explains the difference between the intensities of exercise protocols. It is known that IL-6 attracts lymphocytes to the circulation together with β-adrenergic signalling during exercise [67]; however, there is a higher release of IL-6 within exercise protocols with higher energetic demand, such as the higher volume and during regimens [85][86][87], which do not agree with our findings. Finally, exercise hypoxia may explain at least part of the changes in T lymphocytes and NK counts with exercise, possibly mediated by the same neuroendocrinological factors released by other stress conditions (i.e.,: catecholamines and cortisol) [57,88]. ...
Effect of Exercise on Acute Senescent Lymphocyte Counts: A Systematic Review and Meta-Analysis
Article
  • Jan 2022
Background: Highly differentiated, senescent lymphocytes are pro-inflammatory and contribute to age-related systemic inflammation, called inflammageing. There are several reports of acute changes in senescent lymphocyte counts post exercise, which potentially have consequences for systemic inflammation. However, there is little consensus since the studies differ with respect to participants, exercise protocols, cellular markers assessed, and the time point of assessment post exercise. Objective: We performed a systematic review and meta-analysis to assess the impact of exercise on senescent lymphocyte counts in blood immediately, 1 h and 2 h post exercise. Methods: The search was performed in PubMed (MEDLINE), Web of Science, Embase, Scopus, and Cochrane, on January 11, 2021. The 13 studies selected tested aerobic exercise effects, mainly in young men. They assessed the counts of lymphocytes (CD4 T cells, CD8 T cells, and NK cells), with the following immune cell marker combinations: KLRG1+, CD57+ (only NK cells), EMRA T cells (CD45RA+CCR7-CD28-CD27-), CD28-CD27-, KLRG1+CD28-, and CD28-. Independent extraction of articles was done by 2 researchers. Results: Standardized mean difference (SMD) and 95% confidence interval between baseline and post exercise showed significant increase (SMD >0.9, p < 0.003) in all types of senescent lymphocytes counts immediately post exercise. At 1 h post exercise, senescent CD4 T cells returned to baseline values (p = 0.74), CD8 T cells were reduced (-0.26 [-0.41; -0.11], p = 0.001), and senescent NK cells were raised (0.62 [0.14; 1.10], p = 0.01) above baseline. By 2 h post exercise, senescent CD4 T cells were reduced (-0.94 [-1.40; -0.48], p < 0.001), CD8 T cells remained below baseline (-0.53 [-1.04; -0.009], p = 0.04), and NK cells had returned to baseline values (-0.29 [-0.64; 0.07], p = 0.11). The main determinants of heterogeneity between studies were cytomegalovirus (CMV) serostatus and the characteristics of exercise protocols. CMV+ individuals had a higher immediate lymphocytosis and 1 h post lymphopenia than CMV- individuals. Exercise performed at higher intensities and shorter durations led to higher magnitude of change in senescent lymphocyte counts at all time-points. Conclusion: The differing effects of exercise on senescent NK cells and CD4 and CD8 T cells suggest differing susceptibility to factors modulating lymphocyte extravasation such as adrenaline and exercise intensity.
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... The training protocols did not affect the WBC count (i.e., S2 vs. S1), but higher values were evident after the half-marathon (S3), reaching significance for the HIIT group. Similar increases were observed in other studies of runners [22,32,33]. The increase in WBC after prolonged exercise may indicate neutrophil marginalization or inflammation secondary to tissue destruction, as suggested elsewhere. ...
... Duca et al. [22] found a 62% increase in the number of polymorphonuclear neutrophils just after finishing a half-marathon, which reverted to normal by 48 h. After high intensity effort, increases in the circulating WBC count have been observed for up to 12 h, with differences in leukocytosis depending on the terrain in which the exercise is performed [33]. Given that our results show a greater and significant increase in the HIIT group, we conclude that the type of training affects the magnitude of response, being greater with greater intense and eccentric loads. ...
Benefits on Hematological and Biochemical Parameters of a High-Intensity Interval Training Program for a Half-Marathon in Recreational Middle-Aged Women Runners
Article
Full-text available
(1) Background: half-marathon races are popular among recreational runners, with increases in participation among middle-aged and women. We aimed to determine the effects of two half-marathon training programs on hematological and biochemical markers in middle-aged female recreational runners; (2) Methods: ten women (40 ± 7 years) followed moderate intensity continuous training (MICT), based on running volume below 80% V˙O2max, and another ten women followed high intensity interval training (HIIT) at 80%–100% V˙O2max, with less volume, and combined with eccentric loading exercise. Hematology, plasma osmolality, and plasma markers of metabolic status, muscle damage, inflammatory, and oxidative stress were measured before (S1) and after (S2) training and 24 h after the half-marathon (S3); (3) Results: both training programs had similar moderate effects at S2. However, the acute response at S3 induced different alterations. There was a greater decrease in cholesterol and triglyceride levels in MICT and reductions in markers of damage and inflammation in HIIT. Greater variability in some plasma markers at S3 in MICT suggests that there is inter-individual variability in the response to training; (4) Conclusions: HIIT led to better adaptation to the competition maybe because of the repeated exposure to higher oxygen consumption and eccentric loading exercise.
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... In elite athletes several inflammation biomarkers are used -if inconsistently between training centres-to screen for disease, monitor training and recovery and detect over-training. The most frequently used inflammation markers in the field of exercise physiology are white blood cell (WBC) count [10], Interleukin-6 (IL-6), Interleukin-10 (IL-10) [11] and C-reactive protein (CRP) [12]. ...
Cellular Integrative Immune Markers in Elite Athletes
Article
Full-text available
  • Nov 2022
The integrative immune markers neutrophil-lymphocyte-ratio (NLR), platelet-lymphocyte-ratio (PLR) and systemic immune inflammation index (SII) are established markers in clinical patient care. Adoption of these markers in elite athletics might prove beneficial for monitoring training and health. Blood samples of 195 healthy national Olympic squad athletes were collected before a graded bicycle-ergometric exercise test until complete exhaustion. Measurements included white blood cells, lymphocytes and platelets, allowing for the calculation of the integrative immune markers. Correlations between athlete characteristics (sex, age, sporting discipline, training experience, training volume) and integrative immune marker-values were assessed. In a subgroup analysis a second blood sample was collected from 25 athletes at 1 minute after exercise test to assess its effect on the immune marker levels. An inverse correlation between peak power output and SII-level (Pearson correlation coefficient=−.270, p<.001) and NLR-level (Pearson correlation coefficient=−.249, p<.001) was found. Athletes with higher aerobic fitness had significantly lower values of SII and PLR compared to athletes with lower aerobic fitness. An elevated SII (p=.003) and a reduced PLR (p=.001) was documented as acute response to the exercise test. The integrative immune markers might be a promising tool for monitoring training and health in elite athletes.
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... En yaygın olarak tarif edilen hücresel tepki, egzersiz sırasında lökosit miktarındaki artıştır. [7][8][9][10][11][12][13][14] Hazar ve Ateşoğlu, kuvvette devamlılık ve maksimal kuvvet antrenmanı yapan 2 grupta da toplam lökosit sayısının egzersizden hemen sonra arttığını, egzersizden 6 saat sonra artışın devam ettiğini, 24 saat sonra ise egzersiz öncesi seviyelere döndüğünü raporlamıştır. 7 Bununla birlikte, toplam lökosit sayılarındaki bir artışı yorumlarken, farklı fonksiyonel özelliklere sahip NK (Natural killer) hücreleri, T yardımcı hücreleri, vb. ...
Farklı Hava Sıcaklıklarında Yapılan Aerobik Egzersizlerin Bağışıklık Hücrelerine Akut Etkisi - The Acute Effect of Aerobic Exercises in Different Environment Temperatures on Immunity Cells
Article
Full-text available
  • Jan 2021
Organizmaya zarar verebilecek her türden virüs, bakteri, toksin ve tümör hücrelerine karşı organiz-mayı savunma faaliyetlerinin tümü bağışıklık fonk-siyonları olarak adlandırılmaktadır. Vücuda giren yabancı ajanları, fagositoz yaparak yok eden lökosit-ler bağışıklık sisteminin en temel ve aktif elamanla-rıdır. Akut ve kronik olarak yapılan farklı tipteki egzersizlerin metabolizma üzerine olan etkileri bir-Turkiye Klinikleri J Sports Sci. 2021;13(1):1-8 ÖZET Amaç: Egzersizin bağışıklık sistemi üzerine olan etkileri uzun yıllardır sıkça araştırılan bir konudur. Ancak farklı şiddetlerde yapılan egzersizlerin bağışıklık sistemi üzerine olan etkileri büyük ölçüde bili-nirken, farklı hava sıcaklıklarında uygulan egzersizlerin etkileri hak-kında sınırlı sayıda çalışma vardır. Bu çalışmanın amacı, farklı hava sıcaklıklarında yapılan aerobik egzersizin bağışıklık hücrelerine olan etkilerini araştırmaktır. Gereç ve Yöntemler: Araştırmaya 27 sağlıklı genç birey gönüllü olarak katılmıştır. Katılımcılara 3 farklı sıcaklıkta (0,12 ve 24 °C) 40 dk'lık aerobik koşu egzersizi uygulanmıştır. Koşu hızı, katılımcıların maksimum kalp atım hızlarının %65-70'ine (%50-55 VO2maks) karşılık gelen aralıkta tutulmuştur. Katılımcılardan, eg-zersizlerin öncesinde ve sonrasında kan örnekleri alınmıştır. Katılımcıların bağışıklık fonksiyonları için lökosit ve alt grupları (len-fosit, monosit ve granülosit) kan sayımı ile venöz kan örneklerinden belirlenmiştir. Elde edilen verilerin istatistiksel analizleri eşli örneklem t-testi (önce-sonra) ile yapılmıştır. Bulgular: Yapılan araştırma sonu-cunda 0°C ve 12°C sıcaklıklarda yapılan egzersizlerde lökosit (sırasıyla p=0,015 ve p=0,006) ve nötrofil sayıları (sırasıyla p=0,018 ve p=0,021) önemli derecede artarken, 24°C sıcaklıkta ise sadece nötrofil sayılarında (p=0,046) artış görülmüştür. Diğer kan hücrelerinde 3 farklı sıcaklıkta yapılan egzersizlerde de herhangi bir değişime rastlanmamıştır (p>0,05). Sonuç: Sonuç olarak bu çalışma, çevre sıcaklığı değiştikçe aerobik egzersizlere farklı bağışıklık tepkilerinin oluşabileceğini ortaya koymaktadır. Anah tar Ke li me ler: Soğuk; egzersiz; lökosit; lenfosit; monosit; nötrofil ABS TRACT Objective: The effects of exercise on the immune system have been frequently investigated for many years. Although the effects of exercise at different intensities on the immune system are highly known, there are limited studies on the effects of exercise at different environmental temperatures. The aim of this study was to investigate the effects of aerobic exercise on immune cells at different environmental temperatures. Material and Methods: Twenty-seven young healthy subjects voluntarily participated in this study. Participants performed 40 minutes of aerobic running exercise at three different temperatures (0.12 and 24°C). The running speed rate was controlled around 65-70% (50-55% VO2max) of the participants' maximum heart rate. Blood samples were collected from the participants pre-and post-exercise. Leukocytes and subgroups (lymphocytes, monocytes and granulocytes) were measured to assess the immune functions of the participants via the blood count from venous blood samples. Statistical analysis of the data was assessed using paired t-test (pre and post). Results: The findings of this study showed that leukocyte (p=0.015 ve p=0.006, respectively) and neutrophil (p=0.018 ve p=0.021, respectively) counts significantly increased in the exercises performed at 0°C and 12°C, whereas in the exercise at 24 °C only neutrophil count (p=0.046) significantly increased. However, these exercises applied at three temperatures did not any changes in other blood cells (p>0.05). Conclusion: Consequently, this study indicated that different immune responses to aerobic exercise may occur as the environment temperature changes.
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... The results of some previous studies indicate that the increase in the number of peripheral white blood cells during and immediately after exercise is often due to an increase in the number of neutrophils and to a lesser extent lymphocytes. However, the number of monocytes may also increase (Pizza et al., 1995). Some researchers believe that the increase in white blood cells due to exercise is mostly due to skeletal muscle damage. ...
EFFECT OF PROGRESSIVE MUSCLE RELAXATION AND B COMPLEX CONSUMPTION ON BLOOD PH AND BLOOD INFECTION CHANGES CAUSES OF ANXIETY
Article
Full-text available
  • Feb 2021
With regard of the relationship and effect between body and mind, especially on some of the immune system's factors, it is essential to examine the effects and how they are controlled. The purpose of this study was to examine the effect of eight weeks of progressive muscle relaxation and B complex consumption on blood Monocyte, lymphocytes, PH changes result of anxiety. The statistical population of this study was students in secondary school. The sample consisted of two groups of 15 (experimental and control group) who were selected randomly. Tools included a biofeedback device (GSR) to test the level of anxiety and the SPO device (CBC) to measure blood factors. The training groups done programs for 8 weeks, three session and 40 minutes each session and done 4 set, they exercised under the supervision of the researcher and consuming 100mg of B-complex every day. After 8 weeks, biochemical tests and anxiety tests were repeated again. Results showed eight weeks progressive muscle relaxation with B complex consumption have significant effect on blood monocyte, lymphocytes, PH causes by anxiety. As regarding the significant improvement of safety indexes after relaxation exercises and consumption B complex, it is recommended that athletes and people to reduce their dangerous immune system symptoms use the methods of results in the present study.
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... We further found that G-CSF might play an important role in facilitating NRB during DR, and AVA was able to attenuate this function (Fig. 4). CSFs are a group of cytokines that are released from injured skeletal muscles that promote the proliferation, differentiation and activation of hematopoietic cells after ECinduced muscle damage [39][40][41]. Previous research showed that plasma G-CSF levels were significantly elevated several hours after an acute bout of eccentric exercise and reached peak concentrations at 24 to 48 h post exercise [7,[42][43][44][45]. ...
Avenanthramide supplementation reduces eccentric exercise-induced inflammation in young men and women
Article
Full-text available
Abstract Background Avenanthramides (AVA) are a group of di-phenolic acids found only in oats and have shown antioxidant and anti-inflammatory effects in vitro and in vivo. Eccentric muscle contraction is intimately involved in rigorous exercise that activates systemic and local inflammatory responses. The objective of the study is to evaluate whether chronic AVA supplementation could attenuate peripheral inflammatory and immunological markers in human subjects in response to an acute bout of downhill running (DR). Methods Eleven male and thirteen female subjects voluntarily participated in this double-blinded, randomized controlled study and were randomly divided into AVA-supplemented (AVA) or control (C) groups. All subjects conducted a DR protocol at − 10% grade with an intensity equivalent to 75% of their maximal heart rate. Blood samples were collected at rest and various time points (0-72 h) after DR (PRE). After an 8-week washout period, participants received two cookies daily containing either 206 mg/kg (AVA) or 0 mg/kg (C) AVA for 8 weeks. Following the oat supplementation regimen, the DR and blood sampling protocols were repeated (POST). Plasma inflammatory and immunological markers were measured using Multiplex immunoassay and muscle soreness was evaluated with pain rating scale. Results DR increased plasma creatine kinase (CK) activity (P
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FUTBOLDA KAS HASARI VE ZEMİN İLİŞKİSİ KİTAP 2022
Book
Full-text available
  • Nov 2022
Saha zeminlerinin kas hasarı üzerindeki etkisi konusunda yapılan çalışmalardan çıkan sonuçlar tartışmaya açıktır. Bazı çalışmalarda doğal çim ve suni çim zeminlerin kas hasarında farklılık yaratmadığı, bazılarında ise farklılıkların olduğu açıklanmıştır. Genel kanaat, suni zeminlerin kas hasarı üzerindeki olumsuz etkilerinin daha fazla olduğu yönünde olsa da bu konuda yapılan çalışma sonuçlarına bakıldığında; zeminden ziyade esas etkenin "antrenman ve maç yoğunlukları" olduğu görüşü ağır basmaktadır.
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Downhill Running: What Are The Effects and How Can We Adapt? A Narrative Review
Article
Full-text available
  • Dec 2020
  • SPORTS MED
Downhill running (DR) is a whole-body exercise model that is used to investigate the physiological consequences of eccentric muscle actions and/or exercise-induced muscle damage (EIMD). In a sporting context, DR sections can be part of running disciplines (of-road and road running) and can accentuate EIMD, leading to a reduction in performance. The purpose of this narrative review is to: (1) better inform on the acute and delayed physiological effects of DR; (2) identify and discuss, using a comprehensive approach, the DR characteristics that affect the physiological responses to DR and their potential interactions; (3) provide the current state of evidence on preventive and in-situ strategies to better adapt to DR. Key findings of this review show that DR may have an impact on exercise performance by altering muscle structure and function due to EIMD. In the majority of studies, EIMD are assessed through isometric maximal voluntary contraction, blood creatine kinase and delayed onset muscle soreness, with DR characteristics (slope, exercise duration, and running speed) acting as the main influencing factors. In previous studies, the median (25th percentile, Q1; 75th percentile, Q3) slope, exercise duration, and running speed were − 12% (− 15%; − 10%), 40 min (30 min; 45 min) and 11.3 km h−1 (9.8 km h−1; 12.9 km h−1), respectively. Regardless of DR characteristics, people the least accustomed to DR generally experienced the most EIMD. There is growing evidence to suggest that preventive strategies that consist of prior exposure to DR are the most effective to better tolerate DR. The effectiveness of in-situ strategies such as lower limb compression garments and specific footwear remains to be confirmed. Our review finally highlights important discrepancies between studies in the assessment of EIMD, DR protocols and populations, which prevent drawing firm conclusions on factors that most influence the response to DR, and adaptive strategies to DR.
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The spleen in lymphocyte migration
Article
  • Mar 1988
  • Immunol Today
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Changes of White Blood Cell Count During Prolonged Exercise
Article
  • Sep 1987
Leukocytosis was postulated to accompany short- and medium-length exercise; in this report, we have studied the changes in leukocyte count during and following prolonged exercise. White blood cell (WBC) counts were obtained in 15 endurance-trained subjects before, during, and at a recovery period after an ultralong exercise (120 km march), lasting 24 h. WBC counts increased after 16 h march from a baseline value of 8.5 +/- 0.3 10(9) l-1 to 11.3 +/- 0.8 10(9) l-1 (P less than 0.05) and then declined to 7.1 +/- 0.9 10(9) l-1 after 24 h march with no further significant changes during 64 h of recovery. These observations were supported by previous findings in three separate marches performed by a second group (40, 70, and 120 km). A parallel increase in plasma creatine phosphokinase activity from 127 +/- 4.4 ul-1 to 539 +/- 106.3 ul-1 was observed after 16 h march (P less than 0.01), indicating muscle cell damage. Our findings suggest that in extremely long marches, WBC counts return to baseline values before exercise is terminated. This phenomenon may reflect WBC infiltration to damaged muscle tissue.
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