Recent Progress in Applicability of Exercise Immunology and Inflammation Research to Sports Nutrition

This article focuses on how nutrition may help prevent and/or assist with recovery from the harmful effects of strenuous acute exercise and physical training (decreased immunity, organ injury, inflammation, oxidative stress, and fatigue), with a focus on nutritional supplements. First, the effects of ketogenic diets on metabolism and inflammation are considered. Second, the effects of various supplements on immune function are discussed, including antioxidant defense modulators (vitamin C, sulforaphane, taheebo), and inflammation reducers (colostrum and hyperimmunized milk). Third, how 3-hydroxy-3-methyl butyrate monohydrate (HMB) may offset muscle damage is reviewed. Fourth and finally, the relationship between exercise, nutrition and COVID-19 infection is briefly mentioned. While additional verification of the safety and efficacy of these supplements is still necessary, current evidence suggests that these supplements have potential applications for health promotion and disease prevention among athletes and more diverse populations.

[STRENUOUS AND PROLONGED EXERCISE AND UPPER RESPIRATORY TRACT INFECTION - TREATMENT OR THREAT?]

Prolonged and strenuous exercise may lead to changes in the immune system function and to temporary suppression in defense against pathogens. These changes likely increase the risk of those engaging in prolonged and strenuous physical activity to develop upper respiratory tract infection and to reduce the level of performance. On the other hand, it appears that moderate physical activity reduces the risk of upper respiratory tract infection. Various populations, such as professional athletes and soldiers in combat units, who engage in daily strenuous exercise, may therefore be a high risk group. Integration of additional stress factors, such as sleep deprivation, emotional stress, nutritional deprivation, and dehydration also affect the immune system and may worsen the effect. On the other hand, there are those who claim that upper respiratory symptoms are due to non-infection inflammation causes such as allergy, asthma etc. Hence the effects of strenuous exercise on the immune system during training and competitions are not sufficiently clear. This review article will focus on the known effects of strenuous and prolonged exercise on the immune system, the possible mechanisms leading to these changes and their clinical impacts with applied emphasis to active populations such as athletes and soldiers.

Muscle damage and immune responses to prolonged exercise in environmental extreme conditions

BACKGROUND

This study aimed to investigate the effect of prolonged exercise with and without a thermal clamp on leukocyte cell, stress hormones, cytokine and muscle damage responses.

METHODS

Fifteen healthy male volunteers (means±SD: age 22±3 yr; mass 75.8±3.2 kg; maximal oxygen uptake 55±7 mL/min/kg) randomly completed four chamber trials of 1 hour each, in different environment and separated by 7 days. Trials were: 1) exercise induced heating (EX-heating [EX-H]: temperature/humidity, 38° C/50%); 2) exercise with a thermal clamp (EX-cooling [EX-C]: temperature/humidity, 18° C/50%); 3) passive heating (PA-H: temperature/ humidity, 38° C/50%); 4) passive cooling (PA-C: temperature/ humidity, 18° C/50%). EX-H and EX-C were composed of 1h treadmill runs at 80% individual anaerobic threshold (IAT). Blood samples were collected at pre-post, and 1h postenvironments exposure.

RESULTS

Compared to EX-H, exercise-induced increases in core temperature, heart rate, cortisol, human growth hormone (hGH)), Interleukin-6 (IL-6), leukocyte counts and creatine kinase (CK) and Myoglobin (Mb) were significantly (P<0.01) more pronounced than in EX-C.

CONCLUSIONS

These results suggest that the additional impact of elevated ambient temperatures on stress responses to endurance exercise in trained subjects seems to affect primarily the hormonal systems and resulting changes in leukocyte number, creatine kinase, Myoglobin and interleukine-6.

[The influence of physical load on the propriate immune and physiological parameters.]

Chronic fatigue syndrome is a disease detected in recent 15 or 20 years. Overtrained athletes, people living in stress, the ones with disturbed immunity or people suffering from some of the infectious diseases are the most threatened ones. During ultra-long-distance run, human immune, physiological a biochemical parameters drift of their physiological ranges. The values could increase or decrease. The samples of serum of ultramarathon runners, who took part in the National Ultramarathon Mastership, were collected and measured before and after the race. The parameters include IgA, IgM, IgG and C3 part of complement. Statistically important increases in IgA and IgG concentrations after the race were observed. The changes of concentrations of IgM and C3 part of complement was not statistically important. IgG is responsible for the activation of complement, secondary immune reactions and the neutralization of bacterial toxins. IgA in the role of muckal imunoglobulin helps immune cells to swallow heterogenous particles, germs and toxins. Our immune syst6m is more threatened by heterogenous infectious diseases and even the chronic fatigue syndrome.

The impact of sleeping with reduced glycogen stores on immunity and sleep in triathletes

PURPOSE

We investigated the effects of a 3-week dietary periodization on immunity and sleep in triathletes.

METHODS

21 triathletes were divided into two groups with different nutritional guidelines during a 3-week endurance training program including nine twice a day sessions with lowered (SL group) or maintained (CON group) glycogen availability during the overnight recovery period. In addition to performance tests, sleep was monitored every night. Systemic and mucosal immune parameters as well as the incidence of URTI were monitored every week of the training/nutrition protocol. Two-ways ANOVA and effect sizes were used to examine differences in dependent variables between groups at each time point.

RESULTS

The SL group significantly improved 10 km running performance (-1 min 13 s, P < 0.01, d = 0.38), whereas no improvement was recorded in the CON group (-2 s, NS). No significant changes in white blood cells counts, plasma cortisol and IL-6 were recorded over the protocol in both groups. The vitamin D status decreased in similar proportions between groups, whereas salivary IgA decreased in the SL group only (P < 0.05, d = 0.23). The incidence of URTI was not altered in both groups. All participants in both groups went to bed earlier during the training program (SL -20 min, CON -27 min, P < 0.05, d = 0.28). In the SL group, only sleep efficiency slightly decreased by 1.1 % (P < 0.05, d = 0.25) and the fragmentation index tended to increase at the end of the protocol (P = 0.06).

CONCLUSION

Sleeping and training the next morning regularly with reduced glycogen availability has minimal effects on selected markers of immunity, the incidence of URTI and sleeping patterns in trained athletes.

Effect of acute exercise and hypoxia on markers of systemic and mucosal immunity

Purpose

To determine how immune markers are affected by acute hypoxic exercise at the same relative intensity.

Methods

Twelve endurance-trained males (age: 28 ± 4 years, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2max: 63.7 ± 5.3 mL/kg/min) cycled for 75 min at 70 % of altitude-specific \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2max, once in normoxia (N) and once in hypobaric hypoxia equivalent to 2000 m above sea-level (H). Blood and saliva samples were collected pre-, post- and 2 h post-exercise.

Results

Participants cycled at 10.5 % lower power output in H vs. N, with no significant differences in heart rate (P = 0.10) or rating of perceived exertion (P = 0.21). Post-exercise plasma cortisol was higher in H vs. N [683 (95 % CI 576–810) nmol/l vs. 549 (469–643) nmol/l, P = 0.017]. The exercise-induced decrease in CD4:CD8 ratio was greater in H vs. N (−0.5 ± 0.2 vs. −0.3 ± 0.2, P = 0.019). There were no significant between-trial differences for adrenocorticotropic hormone, plasma cytokines, antigen-stimulated cytokine production, salivary immunoglobulin-A or lactoferrin. However, there was a main trial effect for concentration [F(11) = 5.99, P < 0.032] and secretion [F(11) = 5.01, P < 0.047] of salivary lysozyme, with this being higher in N at every time-point.

Conclusion

Whether the observed differences between H and N are of sufficient magnitude to clinically impair host defence is questionable, particularly as they are transient in nature and since other immune markers are unaffected. As such, acute hypoxic exercise likely does not pose a meaningful additional threat to immune function compared to exercise at sea level, provided that absolute workload is reduced in hypoxia so that relative exercise intensity is the same.

Sex differences in upper respiratory symptoms prevalence and oral-respiratory mucosal immunity in endurance athletes

The purpose of this study was to examine sex differences in oral-respiratory mucosal immunity and the incidence, severity and duration of upper respiratory symptoms (URS) episodes in endurance athletes during a 16-week winter training period. Blood was collected from 210 subjects (147 men and 63 women) at the start and end of the study for determination of differential leukocyte counts. Timed collections of unstimulated saliva were obtained at the start and at 4-week intervals during the study period. Saliva samples were analysed for salivary antimicrobial peptides and proteins (AMPs). Weekly training and daily illness logs were kept using validated questionnaires. Training loads averaged 11 h/week of moderate-vigorous physical activity and were not different for males and females. The salivary concentration of lysozyme and lactoferrin (both P < 0.04) but not salivary immunoglobulin A (SIgA) or amylase were higher in males than females. Saliva flow rates were significantly higher in males than females (P < 0.03) and consequently so were the salivary secretion rates of lysozyme, lactoferrin and amylase (all P < 0.01) but not SIgA (P = 0.097). Total blood leukocyte, monocyte and lymphocyte counts were not different between the sexes but females had higher numbers of circulating neutrophils (P = 0.040). The average number of URS episodes was 0.6 +/- 0.8 (mean +/- SD) in males and 0.8 +/- 1.0 in females (P = 0.103) and the number of URS days was higher in females (4.7 vs 6.8 days, P < 0.02). The duration of URS episodes was longer in females (11.6 vs 15.5 days, P < 0.03). The findings of this study concur with recent reports of illness incidence at major competitive games indicating that female athletes may be more susceptible than their male counterparts to URS and that lower oral-respiratory mucosal immunity may, in part, account for this.

IL-17, neutrophil activation and muscle damage following endurance exercise

The T-cell subset Th17 is induced partly by interleukin (IL)-6 and activated by IL-23, and produces a proinflammatory cytokine IL-17. Since IL-6 increases dramatically following long-lasting endurance exercise, this response may also stimulate the induction of IL-17 and IL-23 after exercise. The aim of this study was to clarify the dynamics of IL-17 in association with endurance exercise-induced muscle damage and inflammatory responses. Fourteen male triathletes participated in a duathlon race consisting of 5 km of running, 40 km of cycling and 5 km of running. Venous blood and urine samples were collected before, immediately after 1.5 h and 3 h after the race. Plasma and urine were analyzed using enzyme-linked immunosorbent assays (ELISA). Haematological and biochemical variables such as neutrophil activation marker (myeloperoxidase: MPO), muscle damage marker (myoglobin: Mb) and soluble receptor activator of nuclear factor (NF)-KB ligand (sRANKL) were also determined to estimate the biological and pathological significance. Plasma concentrations oflL-6 (+26.0x), MPO (+3.2x) and Mb (+4.9x) increased significantly immediately after the race and IL-17 and IL-23 tended to increase. Furthermore, plasma concentrations of IL-12p40 and sRANKL increased significantly after the race. The measured parameters related to Thl 7 cytokines in the urinary output were closely correlated with each other and muscle damage marker. These findings suggest that IL-17 induced by IL-6 and activated by IL-23 or other IL-17 producing-cells and IL-23 might promote neutrophil activation and muscle damage following prolonged endurance exercise.

[Immune dysfunction in highly skilled athletes and nutritional rehabilitation]

The present review examines the effects of strenuous and moderate exercise on various components of the immune system including humoral and cell immunity. Acute exercise have been found to affect lymphocyte subsets, immunoglobulin levels, the activity of mononuclear phagocytic system, polymorphonuclear leukocytes and cytokine levels, especially IL-1, IL-2, IL-6 and TNF. The extreme type of immune deficiency in sportsmen, in which there are not determine different isotypes of immunoglobulins, there are described as phenomenon of Ig disappearance. The immune suppression is associated with an increased risk of subclinical and clinical infection in athletes. The mechanisms immunodeficiency are multifactorial and include neuroendocrinologocal and metabolic disorders. The immunosuppression in sportsmen may be prevented by use of special diets. Although athletes need to eat a well-balanced basic diet, there are several nutritional factors that are difficult to obtain at a sufficient level from a normal diet since athletes require more nutrients than the recommended daily allowances. Thus, appropriate nutrition enrichment of special products and food supplements containing proteins, amino acids, carbohydrates, vitamins, minerals, antioxidants, probiotics is an essential prerequisite for effective improvement of athletic performance, recovery from fatigue after exercise and ward off immunodeficiency.

Cognitive awareness of carbohydrate intake does not alter exercise-induced lymphocyte apoptosis

OBJECTIVE

The purpose of this investigation was to determine whether cognitive awareness of carbohydrate beverage consumption affects exercise-induced lymphocyte apoptosis, independent of actual carbohydrate intake.

INTRODUCTION

Carbohydrate supplementation during aerobic exercise generally protects against the immunosuppressive effects of exercise. It is not currently known whether carbohydrate consumption or simply the knowledge of carbohydrate consumption also has that effect.

METHODS

Endurance trained male and female (N = 10) athletes were randomly assigned to one of two groups based on either a correct or incorrect cognitive awareness of carbohydrate intake. In the incorrect group, the subjects were informed that they were receiving the carbohydrate beverage but actually received the placebo beverage. Participants completed a 60-min ride on a cycle ergometer at 80% VO₂peak under carbohydrate and placebo supplemented conditions. Venous blood samples were collected at rest and immediately after exercise and were used to determine the plasma glucose concentration, lymphocyte count, and extent of lymphocyte apoptosis. Cognitive awareness, either correct or incorrect, did not have an effect on any of the measured variables.

RESULTS

Carbohydrate supplementation during exercise did not have an effect on lymphocyte count or apoptotic index. Independent of drink type, exercise resulted in significant lymphocytosis and lymphocyte apoptosis (apoptotic index at rest = 6.3 ± 3% and apoptotic index following exercise = 11.6 ± 3%, P < 0.01).

CONCLUSION

Neither carbohydrate nor placebo supplementation altered the typical lymphocyte apoptotic response following exercise. While carbohydrate supplementation generally has an immune-boosting effect during exercise, it appears that this influence does not extend to the mechanisms that govern exercise-induced lymphocyte cell death.

Effect of moderate exercise training on T-helper cell subpopulations in elderly people

CD28 molecule expression on the surface of T cells plays a critical role in upregulation of various cytokines synthesis and T-helper (Th) cell proliferation and differentiation. However aging induces a decrease in CD28 expression and unbalance of Th1/Th2, leading to impairment of Th-cell mediated immune function. The purpose of this study was to assess the effects of moderate exercise training on CD28 expression and the balance of Th1/Th2 cells in elderly people. Forty-eight elderly subjects were assigned to an exercise training group (EXC: 13 males, 15 females; aged 61-76) or a non-exercise control group (CON: 7 males, 13 females; aged 62-79). Subjects in EXC participated in exercise sessions 5-days a week for 6 months. Meanwhile, subjects in CON maintained their normal physical activity levels during the study period. Blood samples were collected before and after the training period. Samples were measured for the number of leukocytes and lymphocytes, as well as for CD3+, CD4+, CD28+CD4+, IFN-gamma+CD4+, IL-4+CD4+ cells. The number of leukocytes, lymphocytes, and CD3+ cells did not change after 6 months in both EXC and CON. The number of CD4+ and CD28+CD4+ cells significantly increased after the training in EXC (P < 0.05), while CON did not show significant changes. In the EXC group, IFN-gamma+CD4+ cell numbers were significantly higher following the training (P < 0.05), but the number of IL-4+CD4+ cells was not changed. In the CON group, there were no significant alterations in IFN-gamma+CD4+ and IL-4+CD4+ cell numbers. In conclusion, moderate exercise training in the elderly is associated with improvement of expression of CD28 on Th cells and Th1/Th2 balances. Therefore, exercise training could up-regulate Th cell-mediated immune functions and be helpful for a decrease in the risk of infections and autoimmune diseases in elderly people.

Biomarkers of muscle and cartilage damage and inflammation during a 200 km run

Ultra-marathon running is frequently associated with muscle fibre damage. However, ultra-marathon related information is scarce. The present study evaluated muscle and cartilage biomarkers, and cytokine secretion during a 200 km running event. Venous blood samples from 54 trained male ultra-marathon runners (mean +/- SD, 45.7 +/- 5.1 years). Plasma creatine phosphokinase (CPK), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate, glucose, high-sensitivity C-reactive protein (Hs-CRP), interleukin-6 (IL-6), TNF- proportional, variant and serum cartilage oligomeric matrix protein (COMP) content were determined before, midway and immediately after the race. CPK increased 90-fold (19-fold at 100 km) from pre-race value and LDH increased 3.7-fold (2.2-fold at 100 km). AST increased 15-fold (5-fold at 100 km) and ALT increased 3.9-fold (2-fold at 100 km). Blood lactate and glucose levels did not change significantly. Hs-CRP increased 23-fold (3-fold at 100 km) and IL-6 increased 121-fold at 100 km, and then remained stable up to 200 km, whereas TNF- proportional, variant did not change significantly. Serum COMP increased 3-fold (1.3-fold at 100 km). Post-run CPK was correlated with LDH (r = 0.62, P < 0.001), Hs-CRP (r = 0.45, P < 0.001), ALT (r = 0.89, P < 0.001), AST (r = 0.97, P < 0.001), and IL-6 (r = 0.61, P < 0.001). The present study demonstrated that blood biomarkers related to muscle and cartilage damage and inflammation were increased during a 200 km run and that this was particularly marked during the second half of the event. Ultra-marathon running clearly has a major impact on muscle and cartilage structures.

Resistance exercise does not affect the serum concentrations of cell adhesion molecules

BACKGROUND

Cell adhesion molecules are proteins expressed on the surface of a variety of cells and mediate the leucocyte response to inflammation. Some of these molecules are released to the plasma as soluble forms, whose presence indicates the degree of vascular endothelial activation or dysfunction. Increased concentrations of soluble adhesion molecules are thought to hamper the immune response and mediate the atherosclerotic inflammatory process. Studies on the effect of exercise on the concentrations of soluble adhesion molecules have almost exclusively used aerobic exercise.

AIM

To assess the effect of resistance exercise on the serum concentrations of five cell adhesion molecules during and immediately after 30 min of exercise in lean and obese participants.

METHODS

Fourteen healthy young men (eight lean and six obese) performed 3 sets of 10 resistance exercises with 10-12 repetitions at 70-75% of one repetition maximum in a circuit training fashion. Venous blood samples were drawn at baseline and at the end of the first, second and third sets. The serum concentrations of vascular cell adhesion molecule-1, intercellular cell adhesion molecule-1, E-selectin, P-selectin and L-selectin were measured in a biochip array analyser.

RESULTS

No significant changes were observed in the concentrations of these cell adhesion molecules during exercise, or between lean and obese participants.

CONCLUSION

Our data indicate that resistance exercise of moderate to high intensity does not affect the serum concentrations of cell adhesion molecules in healthy young lean or obese men, suggesting no considerable negative effect on immune function.

Ibuprofen use, endotoxemia, inflammation, and plasma cytokines during ultramarathon competition

The primary purpose of this study was to measure the influence of ibuprofen use during the 160-km Western States Endurance Run on endotoxemia, inflammation, and plasma cytokines. Subjects included 29 ultramarathoners who consumed 600 and 1200 mg ibuprofen the day before and on race day, respectively, and 25 controls that competed in the race but avoided ibuprofen and all other medications. Blood and urine samples were collected the morning prior to and immediately following the race, and subjects recorded muscle soreness during the week following the race using a 10-point Likert scale (DOMS). Race time (25.8+/-.6 and 25.6+/-.8 h, respectively) and ratings of perceived exertion (RPE, 6-20 scale) (14.6+/-.4 and 14.5+/-.2, respectively) did not differ significantly between ibuprofen users and nonusers. Ibuprofen use compared to nonuse was linked to a smaller increase in urine creatinine (P=.038), higher plasma levels of lipopolysaccharide (group effect, P=.042), and greater increases (pre-to-post race) in serum C-reactive protein and plasma cytokine levels for interleukin (IL)-6, IL-10, IL-8, IL-1 ra, granulocyte colony-stimulating factor, monocyte chemotactic protein 1, and macrophage inflammatory protein 1 beta, but not tumor necrosis factor alpha. Post-race DOMS and serum creatine kinase levels did not differ significantly between ibuprofen users and nonusers (20,621+/-3565 and 13,886+/-3068 microcal/L, respectively, P=.163). In conclusion, ibuprofen use compared to nonuse by athletes competing in a 160-km race did not alter muscle damage or soreness, and was related to elevated indicators of endotoxemia and inflammation.

Immune system adaptation in elite athletes

PURPOSE OF REVIEW

To evaluate the effects of exercise on immune function in relation to infection susceptibility.

RECENT FINDINGS

Postexercise immune function depression is most pronounced when exercise is continuous, prolonged, of moderate to high intensity and performed without food intake. Periods of intensified training that result in overreaching have been shown to chronically depress immune function, with leukocyte functions measured at rest still depressed 24 h after the last exercise bout. Several studies indicate that the incidence of symptoms of upper respiratory tract illness is increased in the days following prolonged strenuous endurance events and it has been generally assumed that this is due to the temporary exercise-induced depression of immune function. More recently it has been proposed that at least some of these symptoms are attributable to inflammation of the upper respiratory tract rather than to infectious episodes.

SUMMARY

Although elite athletes are not clinically immune deficient, it is possible that the combined effects of small changes in several immune parameters may compromise resistance to common minor illnesses. Although it is possible that immune depression linked with prolonged intensive training may determine susceptibility to infection, convincing evidence of a cause and effect relationship remains elusive.

Effects of Unaccustomed and Accustomed Exercise on the Immune Response in Runners

PURPOSE

To test the hypothesis that long-term immunological response may be different after accustomed concentric and unaccustomed eccentric exercise in endurance-trained men.

METHODS

Fourteen highly endurance-trained male runners performed two bouts of high-intensity exercise with at least 2-wk intervals between bouts. Concentric exercise consisted of a 60-min level run with a targeted heart rate of 80% VO2 peak. Eccentric exercise was conducted lying on a specially designed exercise rack, eliciting eccentric action of the musculus quadriceps femoris. Blood samples were taken before and 1, 6, 24, 72, and 144 h after exercise to determine creatine kinase (CK), C-reactive protein (CRP), and interleukin-6 (IL-6). Lymphocyte subset distribution was assessed using flow cytometry.

RESULTS

We found a significant (P < 0.05) increase of CD4 (eccentric: 17%; concentric: 20%), CD3+/CD4+ (16 vs 19%), CD25+ (45 vs 29%), CD25+/CD4+ (27 vs 50%), HLA-DR+ (20 vs 15%), HLA-DR+/CD4+ (16 vs 67%), and CD19+/CD45+ (52 vs 103%) positive lymphocytes 1 h after both exercise bouts. However, eccentric exercise resulted in a significantly higher and longer (6 h) increase of CD25+/CD4+ and HLA-DR+/CD8+ lymphocytes and a peak increase of CK at 72 h. IL-6 and CRP increased only after concentric exercise within the first 24 h. Both exercises resulted in a decrease of monocyte activation (LFA-1: CD18+/CD11a+) after 6 h, with an increase for the eccentric exercise part after 24 h (P < 0.05).

CONCLUSION

Accustomed concentric exercise mainly induced an acute-phase response, with increased CRP, IL-6, and activation of CD4 lymphocyte subsets. Unaccustomed eccentric exercise provided a delayed increase in CK and activation of monocytes and CD4+ and CD8+ subsets. Therefore, the immunological reaction depends not only on the type of contraction but also on the adaptation to the exercise.

Effects of endurance training on intracellular calcium concentration in T lymphocytes

The purpose of the present study was to determine whether 12 months of endurance training reduced [Ca2+]i in T helper (CD4+) lymphocytes in trained (TR) men compared to untrained (UT). Fourteen trained (Ironman triathletes) and nine untrained (sedentary) men volunteered for the study. The TR group averaged 12 km of swimming, 300 km of cycling and 60 km of running per week during the year. Resting blood samples were taken from TR (VO(2peak) 64 +/- 2 ml kg(-1) min(-1)) and UT (VO(2peak) 42 +/- 2 ml kg(-1) min(-1)) subjects every 4 weeks for 52 weeks (October 1, 1999-October 1, 2000). Leukocyte concentration was measured using a full blood count. Unstimulated CD4+ lymphocytes were separated and analysed for changes in free ([Ca2+]i) and total ([Ca2+]t) calcium using flow cytometry. There were no significant differences in leukocyte concentration between UT and TR groups. There were significant differences between TR and UT in [Ca2+]i (October B and November), and [Ca2+]t (January and March). There were also significant sequential monthly changes in both [Ca2+]i and [Ca2+]t for TR and UT groups during the study. Significant increases in [Ca2+]i and [Ca2+]t during summer (January and March) for both TR and UT groups suggest an increase in intracellular signalling during hot weather. [Ca2+]i and [Ca2+]t were significantly lower in TR lymphocytes during November and March, suggesting that endurance training during warmer months may decrease [Ca2+]i through altered intracellular signalling, possibly to maintain lymphocyte function during heat stress.

Age-related loss of associations between acute exercise-induced IL-6 and oxidative stress

IL-6 mediates many aspects of the exercise-induced acute-phase response, including upregulation of antioxidant defenses. Moreover, IL-6 synthesis is regulated in part by oxidative stress. This investigation tested the hypothesis that an IL-6-mediated acute-phase response after exercise provides negative-feedback protection against exercise-induced oxidative stress. Healthy young (n = 16, 26.4 +/- 1.8 yr) and older men (n = 16, 71.1 +/- 2.0 yr) ran downhill for 45 min at 75% maximal oxygen consumption before and after a 12-wk period of supplementation with vitamin E (1,000 IU/day) or placebo. Circulating IL-6 and soluble IL-6 receptors, peripheral mononuclear cell production of IL-6, and IL-6 transcripts in muscle were measured before and within a 72-h time window after each acute exercise bout. At all time points plasma IL-6, IL-6 bioavailability, and C-reactive protein were higher in the older men; yet in response to exercise, young and older subjects experienced similar increases in these factors. Although the magnitude of postexercise changes in acute-phase variables was independent of age, correlations among plasma, mononuclear cell, and muscle IL-6 and oxidative stress were evident only in young men (R2 = 0.64, 0.35, and 0.33, respectively). These changes in circulating IL-6 were closely associated with a prooxidant state (R2 = 0.47), whereas muscle IL-6 mRNA correlated with an antioxidant state (R2 = 0.65). Supplementation with vitamin E did not affect exercise-induced responses or differences between the young and old men in a consistent manner. Therefore, oxidative stress is linked to the acute-phase response after exercise in young men, but not in older men who had elevated acute-phase reactants, suggesting that further research is warranted to determine the basis for these differences.

Can nutrition limit exercise-induced immunodepression?

Prolonged exercise and heavy training are associated with depressed immune cell function. To maintain immune function, athletes should eat a well-balanced diet sufficient to meet their energy, carbohydrate, protein, and micronutrient requirements. Consuming carbohydrate during prolonged strenuous exercise attenuates rises in stress hormones and appears to limit the degree of exercise-induced immune depression. Recent evidence suggests that antioxidant vitamin supplementation may also reduce exercise stress and impairment of leukocyte functions. Further research is needed to evaluate the effects of other antioxidants and dietary immunostimulants such as probiotics and echinacea on exercise-induced immune impairment.

Freewheel running selectively prevents mouse CD4+ intestinal lymphocyte death produced after a bout of acute strenuous exercise

Aerobic exercise increases oxidant stress and leads to apoptosis of mouse intestinal lymphocytes (IL). The purpose of this study was to determine whether freewheel running prevents IL loss 24 h after a bout of strenuous exercise. Mice were randomly assigned to in-cage running wheels with 24 h access (WR) or individual cages without running wheels (NR) for 4 months. WR mice accumulated 364 km over 4 months and had higher cytochrome oxidase activity in the plantaris (p < .05), indicative of training. Total intestinal, CD3alphabeta, CD3gammadelta, CD8alpha, and CD8beta lymphocytes and intracellular glutathione were significantly lower in WR and NR mice 24 h post-exercise. The number of CD4 IL decreased 24 h after exercise in NR (p < .01) but not in WR mice relative to their respective no exercise controls. Thus, freewheel running in mice for 4 months prevented CD4 IL loss after acute exercise.

Ultra-Endurance Exercise and Oxidative Damage

At least 30 minutes of moderate-intensity physical activity accumulated on most, preferably all days is considered the minimum level necessary to reduce the risk of developing cardiovascular disease. Despite an unclear explanation, some epidemiological data paradoxically suggest that a very high volume of exercise is associated with a decrease in cardiovascular health. Although ultra-endurance exercise training has been shown to increase antioxidant defences (and therefore confer a protective effect against oxidative stress), an increase in oxidative stress may contribute to the development of atherosclerosis via oxidative modification of low-density lipoprotein (LDL). Research has also shown that ultra-endurance exercise is associated with acute cardiac dysfunction and injury, and these may also be related to an increase in free radical production. Longitudinal studies are needed to assess whether antioxidant defences are adequate to prevent LDL oxidation that may occur as a result of increased free radical production during very high volumes of exercise. In addition, this work will assist in understanding the accrued effect of repeated ultra-endurance exercise-induced myocardial damage.

Patients with solid tumors treated with high-temperature whole body hyperthermia show a redistribution of naive/memory T-cell subtypes

An activation of the immune system might contribute to the therapeutic effect of whole body hyperthermia (WBH) in cancer patients. We explored immune and endocrine responses in patients undergoing high-temperature WBH. Identical parameters were investigated in a separate group of healthy volunteers undergoing physical exercise to rule out effects of sympathetic activation. Lymphocyte subpopulations, lymphocytic expression of a range of adhesion molecules, and serum concentrations of a variety of hormones and cytokines were assessed in cancer patients undergoing high-temperature (60 min at 41.0-41.8 degrees C) WBH (n = 25) and in a separate group of healthy volunteers (n = 10) performing strenuous physical exercise. WBH induced an increase in human growth hormone (hGH), ACTH, and cortisol as well as in TNF-alpha, IL-6, IL-8, and IL-12R. We observed an increase in natural killer (NK) cells and CD56+ NK T cells shortly after initiation of WBH. In contrast, we found a decrease in T cells expressing L-selectin (CD62L) or alpha4beta7 integrin adhesion molecules mediating homing to lymphatic tissues. Accordingly, we observed a decrease in CD45RA+CCR7+ naive and CD45RA-CCR7+ central memory T cells. Numbers of CD45RA-CCR7- memory effector and CD45RA+CCR7 terminally differentiated T cells, on the other hand, remained unchanged. No comparable changes were observed in the group of healthy volunteers. In conclusion, patients with solid tumors treated with WBH show an increase in NK and NK T cells. In a later phase, plasma concentrations of IL-8, hGH, and cortisol increase, correlated with an influx of neutrophils into the peripheral blood. The alterations in T-cell populations suggest that WBH may induce naive and central-memory T cells to enter lymphatic tissue to await antigen exposure and effector T cells to migrate into peripheral tissues to exert their effector function. Although the exercise group may not be an appropriate control to proof the effect of WBH, these changes were not seen in the healthy volunteers performing physical exercise.

Influence of gender, menstrual phase, and oral contraceptive use on immunological changes in response to prolonged cycling

This study determined the influence of gender, menstrual phase (MP), and oral contraceptive (OC) use on immunological changes in response to endurance exercise. Twelve women and 11 men similar in age, aerobic power, and activity level cycled for 90 min at 65% maximal aerobic power. Women were OC users (n = 6) or nonusers (NOC) and cycled during the follicular (Fol) and the luteal (Lut) phases. Venous blood was collected before and after exercise to determine leukocyte counts, IL-6 concentrations, and cortisol. Higher resting levels of neutrophils (approximately 1.5-fold) and cortisol (approximately 2.5-fold) were found in OC vs. NOC and men. Exercise-induced immune cell count and IL-6 changes were similar between men and NOC, except for an approximately 38% greater lymphocyte response in NOC vs. men (P = 0.07). Neutrophil, monocyte, and lymphocyte responses to exercise during Lut in OC were greater than during Fol and also greater than the responses in men (P < or = 0.003). Changes in immune cell counts were consistently greater during Lut in OC vs. NOC, regardless of MP, but only neutrophil responses reached statistical significance (P = 0.01). The exercise-induced change in IL-6 was approximately 80% greater in NOC vs. OC during Fol (P = 0.06), but it was similar between these groups during Lut. Cortisol changes with exercise were not different between groups or MP. These results highlight the necessity to control for gender, and in particular OC use, when designing studies evaluating exercise and immunology.

[Immune defense is both stimulated and inhibited by physical activity]

Physical exercise may enhance some and depress other immune functions. The biological importance of these changes is not fully elucidated. Acute endurance exercise results in a relatively large redistribution of leukocytes between circulating blood and other tissues, as well as an increase in circulating cytokines. Some of these changes have been related to energy metabolism. A temporal correlation has been observed between altered immune functions and resistance to infections. A post-exercise infection can be either the result of a pre-exercise, sub-clinical infection amplified by the performed work or a novel infection, acquired during a period of decreased immune function shortly after exercise. Animal experiments have demonstrated that the susceptibility to infections after exercise depends on exercise intensity and duration, type of pathogen and time of inoculation. Exercise before inoculation with some bacterial agents can enhance resistance to infection, while exercise during an ongoing viral or bacterial infection worsens symptoms and enhances the risk for complications. Most studies demonstrate a deleterious effect of physical exercise in conjunction with infectious episodes.

Is loaded breathing an inflammatory stimulus?

PURPOSE OF REVIEW

To summarize recent data indicating that loaded breathing generates an inflammatory response.

RECENT FINDINGS

Loaded breathing initiates an inflammatory response consisting of elevation of plasma cytokines and recruitment and activation of lymphocyte subpopulations. These cytokines do not originate from monocytes but are instead produced within the diaphragm secondary to the increased muscle activation. Oxidative stress is a major stimulus for the cytokine induction secondary to loaded breathing. The production of cytokines within the diaphragm may mediate the diaphragm muscle fiber injury that occurs with strenuous contractions, or contribute to the expected repair process. These cytokines may also compromise diaphragmatic contractility or contribute to the development of muscle cachexia. They may also have systemic effects, mobilizing glucose from the liver and free fatty acids from the adipose tissue to the strenuously working respiratory muscles. At the same time, they stimulate the hypothalamic-pituitary-adrenal axis, leading to the production of adrenocorticotropic hormone and beta-endorphins. The adrenocorticotropic hormone response may represent an attempt of the organism to reduce the injury occurring in the respiratory muscles through the production of glucocorticoids and the induction of the acute-phase response proteins. The beta-endorphin response would decrease the activation of the respiratory muscles and change the pattern of breathing, which becomes more rapid and shallow, possibly in an attempt to reduce and/or prevent further injury to the respiratory muscles.

SUMMARY

Loaded breathing is an immune challenge for the body, initiating an inflammatory response. Further studies are needed to elucidate the role of this response in the development of ventilatory failure.

Suppression of viral specific primary T-cell response following intense physical exercise in young but not old mice

Intense exercise to exhaustion leads to increased susceptibility and severity of infections. T cells play an essential role in control of viral infections. Whereas immune suppression is considered as a likely mechanism for exhaustive exercise-induced susceptibility to infection, we know little about viral-specific T-cell response following exhaustive exercise in young or old mice. In this study, one group of female young (10–12 wk) and old (22–24 mo) C57BL/6 mice was exposed to a single bout of intense exercise to exhaustion and immediately infected with lymphocytic choriomeningitis virus (LCMV). Eight days later, at the peak of expansion phase of T-cell response, we used tetramers of MHC class I molecules containing viral peptides to directly visualize antigen-specific CD8 T cells and a sensitive functional assay measuring interferon-γ production at the single-cell level to quantitate the CD8 and CD4 T-cell response. To evaluate the impact of intense exercise during both the initiation and evolution of the expansion phase of the T-cell response, a second group of young and old mice continued their daily bouts of intense exercise to exhaustion over the next 8 days. Our data show that, in young mice, LCMV infection following exhaustive exercise leads to suppression of LCMV-specific CD8 and CD4 T-cell responses, and this suppression effect occurs at the initiation of the expansion phase of viral-specific T cells. However, in old mice, unlike young mice, exhaustive exercise does not cause suppression of LCMV-specific T-cell responses.

Effect of Competitive Training on T-cell Mediated Immune Function in Master's Female Athletes

Interest in the effects of intense exercise training on immune function has grown over the past decade. Currently, data on the immunocompetence of female endurance athletes are limited and do not present a clear picture. The objective of this study was to compare the T-cell mediated immune function of female Master's athletes (41 +/- 4.3 yr) during peak training with age-matched non-athletes (42 +/- 3.6 yr) using non-specific and antigen-specific stimulation. Samples of peripheral venous blood were taken at rest for determination of total circulating T-cell number, sub-population number and CD4 + helper T-cell function. No significant difference in total circulating T-cell number or in the number of cells in each of the tested lymphocyte subpopulations was detected between athletes (n = 19) and non-athletes (n = 20). In athletes, 7.9 % of cells responding to non-specific (PMA and ionomycin) stimulation produced IL-2 versus 3.9 % of responding cells in non-athletes (p < 0.05). No statistical difference was noted between athletes and non-athletes in the percentages of antigen-responding CD4 + helper T-cells producing IL-2 (2.4 % and 2.3 %, respectively). Results of this study suggest that T-cell mediated immune function may not be compromised in female Master's athletes during periods of competitive training.

Chronic glutamine supplementation increases nasal but not salivary IgA during 9 days of interval training

Oral glutamine supplementation during and after exercise abolishes exercise-induced decreases in plasma glutamine concentration but does not affect secretory IgA (sIgA) salivary output. Whether chronic glutamine supplementation during high-intensity interval training influences salivary and nasal sIgA concentration is unknown. The purpose of this study was examine the effects of chronic glutamine supplementation on sIgA during intense running training. Runners (n = 13, body mass 69.9 +/- 2.8 kg, peak whole body oxygen uptake 55.5 +/- 2 ml.kg(-1).min(-1), age 29.1 +/- 2.8 yr) participated in twice-daily interval training for 9-9.5 days, followed by recovery (5-7 days). Oral glutamine supplement (0.1 g/kg) or placebo was given four times daily for the first 14 days. After an overnight fast, venous blood, nasal washes, and stimulated saliva were collected at baseline (T1), midtraining (T2), posttraining (T3), and after recovery (T4). Mood states were assessed by using Profile of Mood States (POMS) inventories. We found that glutamine concentration in resting subjects decreased from T1 to T4 (P < 0.05) and was not altered by supplementation. Salivary IgA concentration and output were unchanged by training or supplementation. Mean nasal IgA across the study period was greater in runners receiving glutamine (264.7 +/- 35.0 microg/mg protein) vs. placebo (172.4 +/- 33.7 microg/mg protein; P < 0.05). POMS analyses indicated that vigor was lower at T3 vs. T1 (P < 0.05) and fatigue was higher at T2 vs. T1 and T4 (P < 0.05). We conclude that chronic glutamine supplementation during interval training results in higher nasal IgA than placebo but does not affect salivary IgA concentration or output.

Carbohydrate intake during endurance exercise increases natural killer cell responsiveness to IL-2

The purpose of this study was to evaluate the effect of high-intensity endurance exercise and carbohydrate consumption on in vitro responsiveness of natural killer (NK) to IL-2 (2.5 U/ml for 24 h). Thirteen male subjects (18-26 yr old; peak O2 consumption = 59.79 +/- 5.13 ml.kg-1.ml-1) were recruited to complete two 1-h (75-80% peak O2 consumption) cycling trials in a random counterbalanced order: carbohydrate (CHO) and placebo (Pla). Venous blood samples were collected before (Pre), immediately (Post), 2 h (2H), and 4 h (4H) after exercise. All resting samples were taken after 15 min of seated rest. NK (CD3-/56+), activated NK (CD3-/56+/69+), helper T cell (Th; CD3+/4+), and cytotoxic T cell (Tc; CD3+/8+) number were measured by using flow cytometry. NK cell activity (NKCA) was determined by using both a 51Cr release assay (NKCA-51) and activated NK cell number (NKCA-69). Immune system variables were not different between CHO and Pla, with the exception of NK cell responsiveness to IL-2, where Post (116.2%) and 4H (48.4%) was significantly greater in CHO (P < 0.05). NK, Th, and Tc were significantly higher Post (40.7, 102.7, and 82.0%, respectively) and lower at 2H (-51.9, -53.3, and -53.2%, respectively) than Pre (time effect). 4H was not different from Pre for NK, Th, and Tc. NKCA was significantly lower 2H (NKCA-51, NKCA-69) and 4H (NKCA-69) than Pre. CHO consumption during exercise did not prevent disruptions in unstimulated immune system function, but it did enhance NK responsiveness to IL-2.

Effects of acute exhaustive exercise and chronic exercise training on type 1 and type 2 T lymphocytes

The present study examined the effects of acute exhaustive exercise and chronic exercise training on type 1 and type 2 T lymphocyte distribution and intracellular cytokine production. Seven endurance-trained male cyclists completed exercise trials to exhaustion before, immediately after, and following 2 weeks of resting recovery from a 6-day intensified training period (ITP). During each trial, resting and post-exercise blood samples were incubated with phorbol 12-myristate 13-acetate (PMA) and ionomycin and stained for T lymphocyte surface antigens (CD3). Cells were then permeabilised, stained for intracellular cytokines and analysed using flow cytometry. Acute exhaustive exercise before and following 2 weeks of recovery from the ITP, but not immediately after the ITP, significantly reduced the circulating percentage and number of lFN-gamma+ (type 1) T cells (P<0.05). In addition, the amount of IFN-gamma produced by stimulated T lymphocytes was decreased (P<0.05) post-exercise during each trial. The percentage and number of interferon (IFN)-gamma+ T lymphocytes was decreased (P<0.05) at rest immediately after the ITP compared with before and following 2 weeks of resting recovery from the ITP. However, the amount of IFN-gamma produced by stimulated T lymphocytes at rest was unaltered following the ITP. Neither acute exercise nor chronic exercise training caused an alteration in the circulating percentage or number of interleukin (IL)-4+ (type 2) T lymphocytes. These results suggest a possible mechanism for the increased incidence of infection reported during chronic exercise training via modulation of type 1/type 2 T lymphocyte distribution.

Immune and oxidative changes during and following the Western States Endurance Run

Changes in immune and oxidative stress parameters were measured in ultramarathon runners competing in the 160-km Western States Endurance Run. Forty-five runners agreed to provide blood and saliva samples the morning before the race event, at the 90-km aid station, and 5 - 10 min post-race. Upper respiratory tract infection (URTI) during the two-week period post-race was assessed retrospectively by telephone interviews. Forty subjects completed 90-km (race time, 13.1 +/- 0.3 h), and 31 completed the 160-km race event (27.0 +/- 0.4 h). The blood neutrophil and monocyte counts rose 249 % and 214 %, respectively, in the 31 finishers. Salivary IgA (sIgA) secretion rate decreased significantly from 508 +/- 40 micro g/min pre-race, to 287 +/- 39 micro g/min at 90-km, and 254 +/- 30 micro g/min post-race (50 % decrease). Significant increases were measured in cytokines at 90-km and post-race, with post-race IL-10 increasing 9.5-fold, IL-1ra 6.1-fold, IL-6 50.2-fold, and IL-8 2.5-fold over pre-race levels. Post-race indicators of oxidative stress, F (2)-isoprostane and lipid hydroperoxides, increased 33 % and 88 %, respectively. Pearson product-moment correlations revealed positive correlations at 90-km between F (2)-isoprostane and IL-6 (r = 0.31, p = 0.048), IL-10 (r = 0.31, p = 0.050), and IL-8 (r = 0.43, p = 0.005), but no other significant relationships between immune and oxidative stress indicators at 90-km and post-race. In the group of runners completing at least 90 km of the race, 26 % reported an URTI episode during the two-week period post-race. A low sIgA secretion rate at 90-km was the best predictor of post-race URTI (173 +/- 34 micro g/min in those who later acquired URTI compared to 325 +/- 40 micro g/min in those without URTI, p = 0.007). In conclusion, a modest correlation was found between cytokines and F (2)-isoprostane at 90-km when the greatest oxidative stress occurred, but no other significant correlations in immune and oxidative stress indicators during and following a 160-km ultramarathon race event were noted. About one in four ultramarathoners reported URTI during the two-week period post-race, and a low sIgA secretion rate mid-race best predicted URTI occurrence.

Glutamine supplementation in vitro and in vivo, in exercise and in immunodepression

In situations of stress, such as clinical trauma, starvation or prolonged, strenuous exercise, the concentration of glutamine in the blood is decreased, often substantially. In endurance athletes this decrease occurs concomitantly with relatively transient immunodepression. Glutamine is used as a fuel by some cells of the immune system. Provision of glutamine or a glutamine precursor, such as branched chain amino acids, has been seen to have a beneficial effect on gut function, on morbidity and mortality, and on some aspects of immune cell function in clinical studies. It has also been seen to decrease the self-reported incidence of illness in endurance athletes. So far, there is no firm evidence as to precisely which aspect of the immune system is affected by glutamine feeding during the transient immunodepression that occurs after prolonged, strenuous exercise. However, there is increasing evidence that neutrophils may be implicated. Other aspects of glutamine and glutamine supplementation are also addressed.

Repeated endurance exercise affects leukocyte number but not NK cell activity

INTRODUCTION/PURPOSE

The purpose of this study was to determine the affects of repeated bouts of exercise in the same day on circulating leukocyte number and NK cell activity (NKCA).

METHODS

Ten males (18-25 yr of age) were chosen to complete four trials: two exercise bouts (TB), AM exercise (AM-EX), PM exercise (PM-EX), and control (CN) in a random, counter-balanced order. Exercise consisted of 1-h cycle ergometry, split into three, 20-min segments (5 min at 50% [V0](2peak) and 15 min at 70% [V0](2peak)), and was separated by a 4-h passive recovery. Blood samples were collected from a peripheral arm vein before, immediately, 2 h, and 24 h after the AM bout, and a second series was drawn for the PM bout. Leukocyte subpopulations were measured by manual counting using a hemacytometer and Wright-Giemsa-stained differential slides. NKCA was measured with a whole-blood 51Cr-release assay against K562 target cells. RESULTS Total leukocyte (13.2 +/- 1.2 x 109 L-1, P < 0.035) and neutrophil (7.6 +/- 0.7 x 109 L-1, P < 0.001) counts were significantly higher after two bouts of exercise than a single exercise bout completed in the morning (leukocyte: 7.8 +/- 0.7 x 109 L-1; neutrophil: 5.2 +/- 0.5 x 109 L-1) or afternoon (leukocyte: 9.9 +/- 0.8 x 109 L-1; neutrophil: 5.6 +/- 0.9 x 109 L-1). Lymphocyte counts were significantly greater (P < 0.001) after PM (4.2 +/- 0.5 x 109 L-1) than AM (3.7 +/- 0.4 x 109 L-1) exercise. NKCA was significantly greater (P < 0.001) after exercise in the afternoon (35.3 +/- 8.1%) than morning (27.2 +/- 5.9%).

CONCLUSION

PM exercise produced a larger increase in NKCA than AM exercise, possibly indicative of an interaction between exercise and a diurnal effect. These data suggest two bouts of endurance exercise in 1 d produce an "additive effect" for total leukocyte and neutrophil counts. and to a lesser degree lymphocyte counts, but did not appear to impact shifts in NKCA.

Strength, workload, anaerobic intensity and the immune response to resistance exercise in women

AIM

The mechanism linking exercise intensity to the magnitude of the immune response is not completely understood. The purpose of this investigation was to determine whether the immune response to resistance exercise was associated with (1) changes in workload or (2) anaerobic exercise intensity.

METHODS

Previously untrained women underwent 6 months of resistance training for lower and upper body (TOTAL, n = 34) or for upper body alone (UPPER, n = 30). Lymphocyte subsets [T (CD3+), CD4+, CD8+, NK and B], functional markers (CD45RA+ and CD45RO+), and mitogen (phytohemagglutinin-M, concanavalin A and pokeweed mitogen) and superantigen (staphylococcus a. cowans)-stimulated proliferation were measured from blood samples collected pre- and post-exercise for a squat resistance exercise consisting of six sets of 10 repetitions at 75% of one repetition maximum. This protocol was performed before (T0) and after 3 (T3) and 6 months (T6) of training.

RESULTS

Lymphocyte recruitment to the circulation and proliferation following resistance exercise did not differ between training groups at any time, although the TOTAL group performed at a higher workload as training progressed. With respect to anaerobic intensity, exercise-induced increases in NK, CD4+, CD8+ and B lymphocyte concentrations were 42 (P = 0.07), 76 (P < 0.05), 72 (P < 0.05) and 242% (P < 0.01) greater in women in the highest compared with the lowest post-exercise lactate quartiles. Lymphocyte proliferation did not differ between lactate quartiles.

CONCLUSIONS

Anaerobic intensity, rather than increased strength and workload, is associated with the number of lymphocytes recruited to the circulation, but not T and B cell proliferation responses.

Impact of elevated ambient temperatures on the acute immune response to intensive endurance exercise

To date, there has been little research examining how elevated ambient temperatures exert an additional effect on the acute immune response to endurance exercise. Seven endurance-trained, non-heat-acclimated men [mean (95% confidence interval): 29.7 (25.9-33.5) years, .VO(2max) 66.3 (61.3-71.3) ml.kg(-1).min(-1)] performed two 60-min treadmill runs (75% .VO(2max)) in two different environments (EX1: 18 degrees C/50% room temperature/relative humidity and EX2: 28 degrees C/50% room temperature/relative humidity) with a 7-day interval between the runs. Blood samples were drawn at rest and 0, 0.5, 3, 24, and 48 h after exercise. Compared to EX1, exercise-induced increases in core temperature, sweating rate, heart rate, plasma norepinephrine, cortisol, human growth hormone, and neutrophil and monocyte counts were significantly (5% level) more pronounced after EX2. In contrast, responses of plasma epinephrine, myeloperoxidase, interleukin (IL)-6 as well as lymphocyte counts were similar in EX1 and EX2. Plasma concentrations of IL-8 and C-reactive protein were affected by neither exercise nor by additional heat exposure. Our results suggest that the additional impact of elevated ambient temperatures on stress responses to endurance exercise in trained subjects seems to affect primarily the cardiocirculatory and hormonal systems, and resulting changes in neutrophil and monocyte cell-trafficking. In contrast, heat stress does not seem to exert large additional effects on the acute immune response to endurance exercise as performed in the present study.

Prolonged suppression of the innate immune system in the horse following an 80 km endurance race

REASONS FOR PERFORMING STUDY

An increased susceptibility to bacterial and viral infections of the respiratory tract, which results in a loss of performance, has been reported in racehorses. Much research has focused on the influence of high-intensity exercise of a short duration on immune system function in horses, but scant attention has been given to prolonged endurance exercise as an immune modulator.

OBJECTIVES

The objective of this study was to evaluate the effect of an 80 km endurance race on the monocyte and neutrophil oxidative burst, serum cortisol, glutamine and plasma glucose concentrations in 8 endurance-trained horses (mean +/- s.d. age 9.4 +/- 2.2 years).

METHODS

Blood samples were drawn from the horses prior to and following an 80 km ride.

RESULTS

Mean time for completion of the 80 km race was 306 +/- 40 mins. Immediately post race mean serum cortisol concentration, blood monocyte and neutrophil counts were higher and blood lymphocyte counts and plasma glucose concentration were lower compared with prerace values (P < 0.05). Neutrophil and monocyte oxidative burst activity decreased following the race and had not regained prerace values after 3 days of rest (P < 0.05).

CONCLUSIONS

The present study indicates that long duration exercise in horses has a negative impact on the function of the innate immune system that lasts several days post race. Precise mechanisms instigating the fall in innate immune system function are unclear and multifactorial, but may be attributed, at least in part, to a high serum cortisol response during very prolonged exercise.

POTENTIAL CLINICAL RELEVANCE

A prolonged bout of exercise results in a long-term suppression of the innate immune system function in horses which may, in part, account for the observed increase of infectious episodes in horses during training.

Modulation of immune responses by treadmill exercise in Sprague-Dawley rats

AIM

The duration-dependence of the effect of forced treadmill exercise on the immune system is a subject of ongoing research. In this study, the effect of forced treadmill exercise on immune responses was investigated by evaluating the lymphocyte subset fractions in the peripheral blood and spleen of Sprague-Dawley rats.

METHODS

EXPERIMENTAL DESIGN

Comparative investigation over 8 weeks.

SETTING

Experimental animal laboratory.

PARTICIPANTS

Male Sprague-Dawley rats 5 weeks of age, weighing 150+/-10 g.

INTERVENTIONS

Animals were randomly assigned to one of the 4 following groups: the control group, the 1-week-exercise group, the 4-week-exercise group, and the 8-week-exercise group.

MEASURES

Lymphocyte subset fractions, including those for T, B, CD4+, and CD8+ cells and the T/B and CD4+/CD8+ ratios in the peripheral blood and spleen were measured via flow cytometric analysis after treadmill exercise.

RESULTS

The T cell and CD4+ cell fractions in both the peripheral blood and spleen were increased significantly after 8 weeks of treadmill exercise, but the B cell and CD8+ cell fractions did not change significantly.

CONCLUSION

From the results of the present study, it is suggested that a period of one week is insufficient to eliminate the effects of exercise-induced stress, that 4 weeks are needed to return to the control state, and that at least 8 weeks are needed in order for exercise of moderate intensity to have a positive effect on the immune system.

Increased airway inflammatory cells in endurance athletes: what do they mean?

BACKGROUND

Inflammatory cells are increased in the airways of endurance athletes, but their role in causing exercise-induced respiratory symptoms and bronchoconstriction, or their possible long-term consequences, are uncertain.

AIM

To put the results of athlete studies in perspective, by analysing the pathogenesis of airway cell changes and their impact on respiratory function.

RESULTS

Athletes of different endurance sports at rest showed increased airway neutrophils. Elite swimmers and skiers also showed large increases in airway eosinophils and lymphocytes, possibly related to chronic, exercise-related exposure to irritants or cold and dry air, respectively. Post-exercise studies reported variable responses of airway cells to exercise, but found no evidence of inflammatory cell activation in the airways, at variance with exercise-induced neutrophil activation in peripheral blood. The increase in airway inflammatory cells in athletes can result from hyperventilation-induced increase in airway osmolarity stimulating bronchial epithelial cells to release chemotactic factors. Hyperosmolarity may also inhibit activation of inflammatory cells by causing shedding of adhesion molecules, possibly explaining why airway inflammation appears 'frustrated' in athletes. Data on exhaled nitric oxide are few and variable, not allowing conclusions about its usefulness as a marker of airway inflammation in athletes, or its role in modulating bronchial responsiveness.

CONCLUSIONS

The acute and long-term effects of exercise on airway cells need further study. Airway inflammatory cells are increased but not activated in athletes, both at rest and after exercise, and airway inflammation appears to regress in athletes quitting competitions. Altogether, these findings do not clearly indicate that habitual intense exercise may be detrimental for respiratory health. Rather, airway changes may represent chronic adaptive responses to exercise hyperventilation. An improved understanding of the effects of exercise on the airways will likely have a clinical impact on sports medicine, and on the current approach to exercise-based rehabilitation in respiratory disease.

Exhaustive exercise and type-1/type-2 cytokine balance with special focus on interleukin-12 p40/p70

It is known that interleukin (IL)-12 p70 promotes the differentiation of type-1 helper T (Th1) cells, which produce type-1 cytokines such as IL-2 and interferon (IFN), thereby supporting cellular immunity, whereas IL-12 p40 acts as an antagonist of IL-12 p70. In contrast, IL-4 and IL-6 promote the differentiation of Th2 cells, which produce type-2 cytokines IL-4, IL-6 and IL-10, induce humoral immunity and are involved in allergic reactions. Exhaustive exercise causes the suppression of T lymphocyte activity while asthmatic and allergic diseases are subclinically more prevalent in athletes. One of the mechanisms behind these observations might be a lower type-1 and higher type-2 cytokine balance, which we previously demonstrated to occur after exhaustive exercise. In the present study, we investigated the type-1/type-2 cytokine balance by measuring plasma concentrations of IL-2, IL-4, IL-5, IL-10, tumor necrosis factor (TNF)-alpha and IFN-gamma with microparticle-based flow cytometric technology. IL-5, IL-6 and IL-13 were measured by enzyme-linked immunosorbent assay (ELISA). IL-12 p40 and p70 were measured separately, also by ELISA. Plasma IL-12 p40 concentration rose significantly after maximal exercise and to an even greater extent after a marathon race. Conversely, plasma IL-12 p70 could not be detected even using two different assays. The marathon race caused a marked increase in the plasma concentrations of IL-6 and IL-10. Their responses were correlated (r = 0.78, p < 0.01), indicating that IL-6 is an inducer of IL-10, and may partly induce the type-1 < type-2 cytokine balance. With the exception of one study involving maximal exercise, other studies have failed to show any change in circulating IL-12 concentration with exercise. The present study demonstrated that IL-12 p40 was present in excess of p70 especially after exercise. This may be one of the mechanisms behind several phenomena including cellular immunosuppression, an increase in the relative proportion of type-2 cytokines following exhaustive exercise, and the higher incidence of infections and allergic disorders in regularly exercising endurance athletes.

Expression of CD94 and 56(bright) on natural killer lymphocytes - the influence of exercise

This study was undertaken to determine the effects of acute intense exercise on the cell membrane-bound glycoprotein designated cluster of differentiation (CD) 94. This marker on natural killer (NK) lymphocytes contributes to control of cell function. CD94 was measured on natural killer lymphocytes from 11 adult (average 25 yrs), well-trained male subjects, (Vdot;O 2 peak mean, 5.01 L x min -1) before and immediately after a final, 4 min all-out, cycle ergometry test. Using flow cytometry, lymphocyte populations were distinguished as either having (CD94 +) or lacking (CD94 -) the cell marker. The absolute number of CD94 + and CD94 - natural killer cells increased with exercise but the mean fluorescence intensity (MFI) for CD94 decreased from pre 131, to post 117 (p = 0.01). The percentage of NK cells that were CD94 + did not change, but exercise did mobilise natural killer cells of greater MFI for the surface markers designated CD16/CD56 (pre 750 to post 1 050, p < 0.001). The latter suggests that some exercise-mobilised natural killer cells may have originated from the liver as CD56 +bright cells.

Performance enhancement with maintenance of resting immune status after intensified cycle training

BACKGROUND

Unaccustomed intense endurance exercise is associated with short-term suppression of natural immunity. However, it is not established whether intensified endurance training alters resting immune status or increases the risk of upper respiratory infection (URI).

PURPOSE

This study examined the effect of intensified endurance training for performance enhancement on resting immune status in nine healthy, male competitive cyclists.

DESIGN

Data were collected during 4 weeks of usual training (baseline), followed by prescribed cycle training that consisted of volume-building at customary training intensity (V phase, 6 weeks), unaccustomed very high intensity interval training at 100% maximal heart rate (I phase, 18 days), and an unloading taper (U phase, 10 days).

METHODS

The main performance criterion was a simulated 20 km time-trial. Aerobic capacity measures included power output at ventilatory threshold (POT(vent)) and maximal oxygen uptake (VO(2max)). Markers of immune status (lymphocyte subset counts, serum cytokine levels, and new URI cases) and physiological indicators of training stress (cycling economy, 24-hour urinary cortisol excretion, and serum testosterone concentration) were evaluated in the rested state, 36 to 44 hours postexercise, during baseline, and after each training phase.

RESULTS

Time-trial performance, POT9(vent), VO(2max), and cycling economy improved significantly (p < 0.001) after the V phase, and remained higher than baseline (p < 0.001) after the I and U phases. As compared with the V phase, performance time was faster after the U phase (p < 0.01). In contrast, lymphocyte counts, cytokine levels, incidence of URI, cortisol excretion, and serum testosterone concentration were not significantly different from baseline in any phase.

CONCLUSIONS

Cycling efficiency and performance improved while resting immune status was maintained throughout the 10-week training program. This study provides encouraging data in support of immunological robustness during intensified endurance training.

Prolonged exercise, lymphocyte apoptosis and F2-isoprostanes

Exercise induces a post-exercise decline in the number of circulating lymphocytes. The aim of the present study was to investigate whether strenuous exercise induces lymphocyte apoptosis and generation of reactive oxygen species. Eleven healthy male subjects exercised for 2.5 h on a treadmill. Apoptotic lymphocytes were defined by being annexin positive and 7-aminoactinomycin-D negative. Measurement of F(2)-isoprostanes was used as a marker of oxidant stress in vivo. An increase (60%, P<0.05) in the percentage of apoptotic circulating lymphocytes was found 2 h post-exercise, whereas the total number of apoptotic cells did not change in relation to exercise. The concentration of plasma F(2)-isoprostanes increased approximately 1.6-fold in response to exercise, but declined towards pre-exercise values within the 1st h of recovery. The plasma concentrations of adrenaline, noradrenaline and cortisol increased during exercise. In conclusion, the results of the present study demonstrate that even in a study design in which high levels of apoptosis-inducing factors are generated, such as cortisol and isoprostanes, lymphocyte apoptosis does not contribute to post-exercise lymphocytopenia.

Basal expression of leukocyte iNOS-mRNA is attenuated in moderately endurance-trained subjects

Nitric oxide (NO) is generated in immunocompetent cells by inducible NO-synthase (iNOS), and plays an important role in host defense. However, when produced in large amounts, NO can also exert damaging effects, a scenario that is observed during several inflammatory processes. In the study presented here, we investigated the impact of moderate endurance training (running volume: mean 53.1 km x week(-1), 95% confidence interval 41.2-65.1 km week(-1)) on the leukocyte expression of iNOS mRNA. Semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) analysis was used to examine iNOS mRNA expression in total leukocyte samples from 12 male trained subjects (TR) and a control group of 12 untrained men (UT) at rest. Relative iNOS mRNA levels (iNOS/beta-actin) were higher in UT (0.88, 0.73-1.03) when compared with TR (0.34, 0.09-0.58, P<0.001). iNOS mRNA was not detectable in 5 of the 12 TR subjects. These initial results show that the basal expression of iNOS mRNA is downregulated by moderate endurance training. Further research should clarify whether regular training also affects the responsiveness of leukocyte iNOS gene expression to stimulatory signals. It would be of interest to establish whether moderate training can exert a suppressive and therefore therapeutic effect on the elevated levels of expression of iNOS observed in, for example, several inflammatory disorders.

[Effect of aerobic endurance exercise on immune function in elderly athletes]

Recently, there have been several reports on the influence of physical activity on immune function. Most of the studies were conducted using maximal exercise in young and middle-aged subjects. Since human immune function undergoes adverse changes with aging, we investigated in the present study whether submaximal, aerobic exercise induces changes in immune function in elderly subjects. Leukocytes, differential blood count, subsets of lymphocytes, CD4/CD8 ratio and immunoglobulins were studied after submaximal aerobic exercise (mean lactate 2.57 + 0.3 mmol/l) in 15 elderly subjects (mean age 68 +/- 5.6 years). These parameters were measured before, immediately after and 4 hours after exercise. Mean hemoglobin was unchanged indicating no hemoconcentration. There was a small increase in mean total lymphocytes (p < 0.05 immediately after exercise), while there was a highly significant increase in leukocyte count both immediately and 4 hours after exercise (p < 0.01). We found a significant correlation between the increase in leukocytes and lactate concentration (p < 0.01, r = 0.784). Lactate levels of all subjects were below 4 mmol/l. These results might indicate that the effect of a single bout of aerobic exercise on immune function depends on the intensity and duration of exercise relative to the level of fitness in elderly subjects. There was a highly significant rise (p < 0.001) in CD4/CD8 ratio 4 hours after exercise. This increase was mainly due to a rise in CD4 cell number whereas T-suppressor cells were almost unchanged. Our data show a possible stimulation of immune function by a submaximal, aerobic exercise in elderly subjects. Further studies are required to clarify whether a stimulation of CD4/CD8 ratio by chronic training gives rise to a reduction of infections in physically active elderly persons.

Differential cell adhesion molecule expression and lymphocyte mobilisation during prolonged aerobic exercise

This study was undertaken to determine the cell adhesion molecule profile of CD4+, CD8hi and CD56+ lymphocytes, which are mobilised to and from the peripheral blood during and after prolonged aerobic exercise. Ten healthy males (21-35 years old) were tested on two occasions, separated by at least 14 days. On the first occasion, subjects were examined in a rested state but did not exercise. On the second occasion, the same subjects were examined at the same time of day before, during and after 2 h of exercise at 65% of peak oxygen consumption. Blood samples obtained at rest (t0), during (at 0.5, 1, 1.5 and 2 h, t0.5, t1, t1.5 and t2, respectively) and after (at 4 and 24 h, t4 and t24, respectively) exercise were analysed by two-colour flow cytometry for CD4+, CD8hi and CD56+ cell surface expression, and density of CD62L, CD49d and CD11a. At t2, circulating concentrations of CD56+, CD8hi and CD4+ lymphocytes had increased (P < 0.05) by 330%, 105% and 30%, respectively. The majority of CD4+, CD8hi and CD56+ lymphocytes mobilised to the blood at t2 were CD62L- and CD11ahi, although populations of CD4+ and CD56+ cells that expressed CD62L+ and CD11alo were also mobilised. Changes in subset concentrations at t0.5 were positively associated (r = 0.63; P < 0.01) with their corresponding mean surface density of CD11a at t0. Our findings suggest that the differential mobilisation of lymphocytes during prolonged aerobic exercise is linked to the surface expression of CD11a (i.e. lymphocyte-function-associated antigen-1). However, mechanisms unrelated to CD11a expression also appear to be involved.

Circulating monocytes are not the source of elevations in plasma IL-6 and TNF-alpha levels after prolonged running

The present study was undertaken to examine the effect of prolonged running on monocyte intracellular cytokine production and plasma cytokine concentration. Blood samples were collected 1 h before, immediately after, 2 h after, and 24 h after a competitive marathon run. There was no change in the number of cells spontaneously producing tumor necrosis factor (TNF)-alpha; however, there was a decrease in the number of cells producing interleukin (IL)-1alpha and IL-6 (P < 0.01) postexercise. In contrast, there was an increase in the number of monocytes that responded to lipopolysaccharide stimulation by producing IL-1alpha, TNF-alpha, and IL-6 (P < 0.01) immediately and 2 h postexercise; however, these cells contained less cytokine (P < 0.05). Plasma IL-6, TNF-alpha, epinephrine, norepinephrine, and cortisol concentrations were markedly increased (P < 0.01) postexercise. These data demonstrate that circulating monocytes are not the source of elevated levels of plasma IL-6 and TNF-alpha after prolonged running. In addition, it is likely that stress hormones result in a decrease in the amount of cytokine produced by LPS-stimulated cells postexercise.

Active recovery and post-exercise white blood cell count, free fatty acids, and hormones in endurance athletes

Strenuous endurance exercise in fasted subjects is accompanied by increased plasma levels of catecholamines, leucocytosis, low insulin, and elevated plasma free fatty acids (FFA). Immediately after such exercise, plasma FFA may rise to high and potentially harmful levels, whereas the white blood cell count (WBCC) rapidly decreases towards or below baseline values. The present work investigated how active recovery (AR) for 15 min at 50% of maximal oxygen consumption (VO2max), after 60 min of uphill running at 83% of VO2max, influenced plasma FFA, lymphocyte, neutrophil, granulocyte, and monocyte count, as well as adrenaline, noradrenaline, insulin and cortisol concentrations until 120 min post-exercise. Thirteen endurance athletes participated in the study [24.2 (3.7) years, 1.82 (0.06) m, 76.7 (7.9) kg and VO2max 69.2 (6.8) ml min-1 kg-1]. In a randomized order, the subjects completed two sets of strenuous workouts, followed by either AR or complete rest in the supine position (RR). Compared with RR, AR strongly counteracted the rapid increase in plasma FFA 5 min post-exercise. The decreases in neutrophil and monocyte counts post-exercise were nullified by AR, and the cell count stayed above resting values throughout the observation period. AR also counteracted the rapid return of hormone concentration towards baseline levels. It would appear that active recovery at low intensity after strenuous exercise can maintain sufficient adrenergic activation to counteract the post-exercise drop in WBCC. However, in spite of keeping the catecholamine concentration high and insulin levels low, AR can also maintain a low plasma FFA concentration, probably because of the continued use of FFA in muscle. It remains to be elucidated whether the observed high FFA and low WBCC values after RR have a negative effect on health. If so, AR could be a preventive measure.