Exercise immunology: nutritional countermeasures

International society of sports nutrition position stand: energy drinks and energy shots

Position Statement: The International Society of Sports Nutrition (ISSN) bases the following position stand on a critical analysis of the literature regarding the effects of energy drink (ED) or energy shot (ES) consumption on acute exercise performance, metabolism, and cognition, along with synergistic exercise-related performance outcomes and training adaptations. The following 13 points constitute the consensus of the Society and have been approved by the Research Committee of the Society: Energy drinks (ED) commonly contain caffeine, taurine, ginseng, guarana, carnitine, choline, B vitamins (vitamins B1, B2, B3, B5, B6, B9, and B12), vitamin C, vitamin A (beta carotene), vitamin D, electrolytes (sodium, potassium, magnesium, and calcium), sugars (nutritive and non-nutritive sweeteners), tyrosine, and L-theanine, with prevalence for each ingredient ranging from 1.3 to 100%. Energy drinks can enhance acute aerobic exercise performance, largely influenced by the amount of caffeine (> 200 mg or >3 mg∙kg bodyweight [BW-1]) in the beverage. Although ED and ES contain several nutrients that are purported to affect mental and/or physical performance, the primary ergogenic nutrients in most ED and ES based on scientific evidence appear to be caffeine and/or the carbohydrate provision. The ergogenic value of caffeine on mental and physical performance has been well-established, but the potential additive benefits of other nutrients contained in ED and ES remains to be determined. Consuming ED and ES 10-60 minutes before exercise can improve mental focus, alertness, anaerobic performance, and/or endurance performance with doses >3 mg∙kg BW-1. Consuming ED and ES containing at least 3 mg∙kg BW-1 caffeine is most likely to benefit maximal lower-body power production. Consuming ED and ES can improve endurance, repeat sprint performance, and sport-specific tasks in the context of team sports. Many ED and ES contain numerous ingredients that either have not been studied or evaluated in combination with other nutrients contained in the ED or ES. For this reason, these products need to be studied to demonstrate efficacy of single- and multi-nutrient formulations for physical and cognitive performance as well as for safety. Limited evidence is available to suggest that consumption of low-calorie ED and ES during training and/or weight loss trials may provide ergogenic benefit and/or promote additional weight control, potentially through enhanced training capacity. However, ingestion of higher calorie ED may promote weight gain if the energy intake from consumption of ED is not carefully considered as part of the total daily energy intake. Individuals should consider the impact of regular coingestion of high glycemic index carbohydrates from ED and ES on metabolic health, blood glucose, and insulin levels. Adolescents (aged 12 through 18) should exercise caution and seek parental guidance when considering the consumption of ED and ES, particularly in excessive amounts (e.g. > 400 mg), as limited evidence is available regarding the safety of these products among this population. Additionally, ED and ES are not recommended for children (aged 2-12), those who are pregnant, trying to become pregnant, or breastfeeding and those who are sensitive to caffeine. Diabetics and individuals with preexisting cardiovascular, metabolic, hepatorenal, and/or neurologic disease who are taking medications that may be affected by high glycemic load foods, caffeine, and/or other stimulants should exercise caution and consult with their physician prior to consuming ED. The decision to consume ED or ES should be based upon the beverage's content of carbohydrate, caffeine, and other nutrients and a thorough understanding of the potential side effects. Indiscriminate use of ED or ES, especially if multiple servings per day are consumed or when consumed with other caffeinated beverages and/or foods, may lead to adverse effects. The purpose of this review is to provide an update to the position stand of the International Society of Sports Nutrition (ISSN) integrating current literature on ED and ES in exercise, sport, and medicine. The effects of consuming these beverages on acute exercise performance, metabolism, markers of clinical health, and cognition are addressed, as well as more chronic effects when evaluating ED/ES use with exercise-related training adaptions.

Effect of Acute High-Intensity Interval Training on Immune Function and Oxidative Stress in Canoe/Kayak Athletes

The aim of this study was to investigate the effects of acute high-intensity interval training (HIIT) on immune function and oxidative stress in male canoe/kayak athletes who were well trained. A total of 22 participants were voluntarily recruited with an age range of 15.9 ± 2.3 years, height of 172.2 ± 5.5 cm, body mass of 63.30 ± 6.95 kg, and body fat of 13.77 ± 3.76%. The modified Wingate kayaking test on a kayak ergometer was performed by all participants. Blood samples were collected at three different time points: before the test (Pre-T), immediately after (Post-T), and 3 h post-test (Post-3 h). Saliva samples were collected at two different time points: before the test (Pre-T) and 3 h after the test (Post-3 h). Results indicated that acute canoe/kayak ergometry HIIT had significant effects on the percentages and counts of leukocytes, neutrophils, lymphocytes, and lymphocyte subsets. Additionally, it resulted in increased total LPS-stimulated neutrophil elastase release and alterations in plasma concentrations of superoxide dismutase, catalase, and TBARS. These findings suggest that conventional kayak HIIT regimens can have short-term effects on immune function and induce oxidative stress in athletes.

Effect of Glutamine Supplementation on Muscular Damage Biomarkers in Professional Basketball Players

Scientific evidence supports the role of L-glutamine in improving immune function. This could suggest a possible role of L-glutamine in recovery after intense exercise. To this end, the present report aimed to study if oral L-glutamine supplementation could attenuate muscle damage in a group of players of a mainly eccentric sport discipline such as basketball. Participants (n = 12) were supplemented with 6 g/day of glutamine (G group) or placebo (P group) for 40 days in a crossover study design (20 days with glutamine + 20 days with placebo and vice versa). Blood samples were obtained at the beginning and at the end of each period and markers from exercise-induced muscle damage were determined. The glutamine supplemented group displayed significantly low values of aspartate transaminase, creatine kinase and myoglobin in blood, suggesting less muscle damage compared to the placebo. In addition, adrenocorticotropic hormone levels were lower in the glutamine supplemented group than in the placebo. As a result, the circulating cortisol levels did not increase at the end of the study in the glutamine supplemented group. Altogether, the results indicate that glutamine could help attenuate exercise-induced muscle damage in sport disciplines with predominantly eccentric actions.

The Long History of Vitamin C: From Prevention of the Common Cold to Potential Aid in the Treatment of COVID-19

From Pauling's theories to the present, considerable understanding has been acquired of both the physiological role of vitamin C and of the impact of vitamin C supplementation on the health. Although it is well known that a balanced diet which satisfies the daily intake of vitamin C positively affects the immune system and reduces susceptibility to infections, available data do not support the theory that oral vitamin C supplements boost immunity. No current clinical recommendations support the possibility of significantly decreasing the risk of respiratory infections by using high-dose supplements of vitamin C in a well-nourished general population. Only in restricted subgroups (e.g., athletes or the military) and in subjects with a low plasma vitamin C concentration a supplementation may be justified. Furthermore, in categories at high risk of infection (i.e., the obese, diabetics, the elderly, etc.), a vitamin C supplementation can modulate inflammation, with potential positive effects on immune response to infections. The impact of an extra oral intake of vitamin C on the duration of a cold and the prevention or treatment of pneumonia is still questioned, while, based on critical illness studies, vitamin C infusion has recently been hypothesized as a treatment for COVID-19 hospitalized patients. In this review, we focused on the effects of vitamin C on immune function, summarizing the most relevant studies from the prevention and treatment of common respiratory diseases to the use of vitamin C in critical illness conditions, with the aim of clarifying its potential application during an acute SARS-CoV2 infection.

Exercise, Immunity, and Illness

It is generally accepted that moderate amounts of exercise improve immune system functions and hence reduce the risk of infection whereas athletes engaged in regular prolonged and/or intensive training have a higher than “normal” incidence of minor infections, especially of the upper respiratory tract (URT, e.g., common cold and influenza). This is likely related to regular acute (and possibly chronic) periods of exercise-induced changes in immune function. URT infections can compromise performance directly if suffered shortly before or during competition or indirectly if suffered at other times via effects on training and/or physiological adaptations. This chapter covers the effects of exercise (acute and chronic), both positive and negative, on immune function and consequent infection risk, and considers the current state-of-the-art for monitoring and assessing this in athletes.

Respiratory Infections

Respiratory infections are the most frequent cause of athletes’ visits in medical practices. Simultaneously, contradictory beliefs are generally held regarding influence of repeated exercise on immunity reflected in susceptibility to infections. Many tend to claim that exercise weakens the immunity and renders regular exercisers more prone to develop airway infections. On the other hand, voices are heard in favor of the possible beneficial influence of regular exercise on immune system efficiency. This chapter focuses on the associations of various kinds of exercise with respiratory infection susceptibility. Influence of exercise, in particular associated with competitive performance, on selected innate and acquired immune response mechanisms is also addressed.

ISSN exercise & sports nutrition review update: research & recommendations

Background

Sports nutrition is a constantly evolving field with hundreds of research papers published annually. In the year 2017 alone, 2082 articles were published under the key words ‘sport nutrition’. Consequently, staying current with the relevant literature is often difficult.

Methods

This paper is an ongoing update of the sports nutrition review article originally published as the lead paper to launch the Journal of the International Society of Sports Nutrition in 2004 and updated in 2010. It presents a well-referenced overview of the current state of the science related to optimization of training and performance enhancement through exercise training and nutrition. Notably, due to the accelerated pace and size at which the literature base in this research area grows, the topics discussed will focus on muscle hypertrophy and performance enhancement. As such, this paper provides an overview of: 1.) How ergogenic aids and dietary supplements are defined in terms of governmental regulation and oversight; 2.) How dietary supplements are legally regulated in the United States; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of nutritional approaches to augment skeletal muscle hypertrophy and the potential ergogenic value of various dietary and supplemental approaches.

Conclusions

This updated review is to provide ISSN members and individuals interested in sports nutrition with information that can be implemented in educational, research or practical settings and serve as a foundational basis for determining the efficacy and safety of many common sport nutrition products and their ingredients.

Cameroonian professional soccer players and risk of atherosclerosis

Background

Elevated titers of antibodies against oxidized low-density lipoproteins-cholesterol (ox-LDL-Ab) have been reported among professional athletes, paradoxically reflecting an increased risk of developing atherogenic and/or cardiovascular events. This study aimed to determine titers of ox-LDL-Ab in a group of Cameroonian professional soccer players, and evaluate their evolution during part of a competition season as well as the plasmatic antioxidant status to find out if this latter correlates with ox-LDL-Ab .

Methods

We conducted a descriptive cohort study in 2012 including 18 healthy male soccer players. Three samplings were performed in March (T1), May (T2), and July 2012 (T3) to assess the lipid profile, titers of ox-LDL-Ab, and plasmatic concentrations of four antioxidants: the ferric reducing antioxidant power (FRAP), reduced glutathione (GSH), superoxide dismutase (SOD), and uric acid.

Results

Ages ranged from 16 to 28 years with a median (interquartile range) of 19.5 (19–23) years. Total cholesterol, high-density lipoproteins-cholesterol (HDL-C), low-density lipoproteins-cholesterol (LDL-C) and triglycerides varied within normal ranges throughout the three samplings. While total cholesterol and LDL-C titers increased significantly (p = 0.003 and p = 0.006, respectively), triglycerides and HDL-C values varied non-significantly throughout the measurements (p = 0.061 and p = 0.192, respectively). The median ox-LDL-Ab titers were respectively: 653.3 (468.2–838.8) mIU/ml at T1, 777.7 (553.7–1150.7) mIU/ml at T2, and 1037.7 (901.7–1481.5) mIU/ml at T3. Overall, ox-LDL-Ab titers increased significantly from T1 to T3 (p = 0.006). Concomitantly, uric acid and FRAP concentrations decreased significantly (p = 0.001 and p = 0.003, respectively); on the contrary, GSH and SOD values increased, but insignificantly (p = 0.115 and p = 0.110, respectively). There was a positive and significant correlation between ox-LDL-Ab and HDL-C (ρ = 0.519, p = 0.027), and between ox-LDL-Ab and SOD (ρ = 0.504, p = 0.033) at T2. Ox-LDL-Ab values were expected to increase with each new visit (β = 201.1; p = 0.041) and each IU/ml of SOD titers (β = 23.6; p = 0.019).

Conclusion

These Cameroonian professional soccer players exhibited high levels of ox-LDL-Ab reflecting elevated levels of oxidatively-modified LDL-C particles with an increment over time, this being insufficiently counterbalanced by the antioxidant defense mechanisms. As a consequence, they may be at increased atherogenic and cardiovascular risks.

Influence of nutrient intake on antioxidant capacity, muscle damage and white blood cell count in female soccer players

Background

Soccer is a form of exercise that induces inflammatory response, as well as an increase in free radicals potentially leading to muscle injury. Balanced nutritional intake provides important antioxidant vitamins, including vitamins A, C and E, which may assist in preventing exercise-related muscle damage. The purpose of the present study was to determine the effect of macro/micronutrient intake on markers of oxidative stress, muscle damage, inflammatory and immune response in female soccer players.

Methods

Twenty-eight female players belonging to two soccer teams of the same professional soccer club participated in this study after being informed about the aims and procedures and after delivering written consent. Each team completed an 8-day dietary record and played one competition match the same week. Participants were divided into two groups: the REC group (who complied with recommended intakes) and the NO-REC group (who were not compliant). Laboratory blood tests were carried out to determine hematological, electrolytic and hormonal variables, as well as to monitor markers of cell damage and oxidative stress. Blood samples were obtained 24 h before, immediately after and 18 h after official soccer matches. Student t-test or Mann–Whitney U-test was used to compare both groups throughout the match.

Results

At rest, we observed that the REC group had higher levels of total antioxidant status (TAS), glutathione peroxidase (GPx), and lower levels of creatine kinase (CK) and lactate dehydrogenase (LDH) in comparison to the NO-REC group. Immediately after the match, levels of TAS, GPx, superoxide dismutase (SOD), LDH and % lymphocytes were higher and the % of neutrophils were lower in the REC group compared to the NO-REC group. These differences were also maintained 18 h post-match, only for TAS and GPx.

Conclusions

Our data reveal an association between nutritional intake and muscle damage, oxidative stress, immunity and inflammation markers. The benefit of the intake of specific nutrients may contribute to preventing the undesirable physiological effects provoked by soccer matches.

Cognitive and behavioural effects of physical exercise in psychiatric patients

The current review outlines the under-appreciated effects of physical exercise on the course of psychiatric disorders, focussing on recent findings from animal and human research. Several studies have shown that regular physical exercise is significantly beneficial for psychiatric patients both on a biological and a psychological level. Positive effects of controlled exercise include improved metabolic responses, neuro-protection, increased quality of life, and reduced psychopathological symptoms. Studies investigating the effectiveness of various physical training interventions in alleviating severe mental diseases, such as Alzheimer's dementia (AD), schizophrenia (SZ) or major depressive disorder (MDD) indicate that physical exercise can relieve symptoms of depression, psychosis and dementia and more importantly can curtail further progression of these diseases. This review assesses the most effective methods of physical training for specific psychiatric symptoms. Introducing physical exercise in therapeutic regimes would be an innovative approach that could significantly reduce the severity of psychopathological and cognitive symptoms in patients. The positive biological and molecular outcomes associated with physical exercise render it a concrete therapeutic strategy for improving the quality of live and reducing physical illness in psychiatric patients. Therefore, integrating physical activity into a patient's social life may be an effective treatment strategy. Furthermore, exercise might have the potential to be a preventative treatment within the context of multi-modal therapeutic programs.

ISSN exercise & sport nutrition review: research & recommendations

Sports nutrition is a constantly evolving field with hundreds of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper is a five year update of the sports nutrition review article published as the lead paper to launch the JISSN in 2004 and presents a well-referenced overview of the current state of the science related to how to optimize training and athletic performance through nutrition. More specifically, this paper provides an overview of: 1.) The definitional category of ergogenic aids and dietary supplements; 2.) How dietary supplements are legally regulated; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of the ergogenic value of nutrition and dietary supplementation in regards to weight gain, weight loss, and performance enhancement. Our hope is that ISSN members and individuals interested in sports nutrition find this review useful in their daily practice and consultation with their clients.

Vitamin C Supplementation and Salivary Immune Function Following Exercise-Heat Stress

Purpose:

Prolonged physical exertion and environmental heat stress may elicit postexercise depression of immune cell function, increasing upper respiratory tract infection (URTI) susceptibility. We investigated the effects of acute and short-term vitamin C (VC) compared with placebo (PL) supplementation on URTI susceptibility, salivary immunoglobulin A (s-IgA), and cortisol responses in healthy individuals following prolonged exercise-heat stress.

Methods:

Twelve participants were randomized into the VC or PL group in a double-blind design. For 12 days, participants consumed 3 × 500 mg tablets of VC or PL per day, with testing completed at baseline, then following acute (1 d) and short-term (8 d) supplementation. Participants performed 120.1 ± 49.6 min of cycling at 54 ± 6% VO2max in a hot (34.8 ± 1.0°C and 13 ± 3% relative humidity) environment, with saliva samples collected at pre-, post-, and 72 h postexercise. Health logs specifying URTI symptoms were completed for 7 days postexercise.

Results:

A 2 × 3 × 3 mixed ANOVA with a post hoc Bonferroni correction factor revealed a significant linear trend in postexercise cortisol attenuation in the VC group, 21.7 ± 15.1 nmol/L (mean ± SD) at baseline, to 13.5 ± 10.0 at acute, to 7.6 ± 4.2 after short term (P = .032). No differences were detected in ratio of s-IgA to protein or URTI symptoms between groups.

Conclusions:

These data suggest that vitamin C supplementation can decrease postexercise cortisol in individuals performing exercise similar to that of a half-marathon or marathon in hot conditions. However, no changes in s-IgA and URTI were evident, possibly due to previous moderate training and reduced physical and psychological stress compared with athletes participating in ultramarathons.

Pre-existing inflammatory state compromises heat tolerance in rats exposed to heat stress

This study investigated the roles of endotoxemia and heat-induced tissue damage in the pathology of heat stroke. In groups of eight, male Wistar rats were treated with heat exposure only (HE), or heat exposure with turpentine (T+HE), dexamethasone (D+HE), and turpentine and dexamethasone combined (TD+HE). The rats remained sedated for 2 h after receiving the respective treatments, followed by heat exposure until the core temperature (Tc) was 42°C for 15 min; control rats received turpentine (T), dexamethasone (D), and turpentine and dexamethasone (TD) without heat stress. Blood samples were collected before treatment ( baseline I), after 2 h of passive rest ( baseline II), at Tc 40°C (T40), and 15 min after achieving Tc 42°C (T42). No rats died in the nonheat-stressed groups. Survival rate was lowest in the TD+HE rats (37.5%), followed by the HE (62.5%), T+HE (75%), and D+HE (100%) rats ( P < 0.05). The duration of survival at T42°C was shortest in the TD+HE rats (9.9 ± 6.2 min) ( P < 0.01), followed by the T+HE (11.3 ± 6.1 min) and the HE (12.2 ± 4 min) ( P < 0.05) rats. The increase in plasma IL-6 concentrations was highest in the T+HE (352%) and HE (178%) rats ( P < 0.05). D+HE treatment suppressed the increases in plasma aspartate transaminase, alanine aminotransferase, and IL-6 and LPS concentrations during severe heat stress. Heat stroke can be triggered by endotoxemia or heat-induced tissue damage, and preexisting inflammation compromises heat tolerance, whereas blocking endotoxemia increases heat tolerance.

Nutritional strategies to counter stress to the immune system in athletes, with special reference to football

Although epidemiological data indicate that athletes are at increased risk of upper respiratory tract infection during periods of heavy training and the 1 - 2 week period following endurance race events, there is very limited information on the responses to football training and match-play. For several hours after heavy exertion, components of both the innate (e.g. natural killer cell activity and neutrophil oxidative burst activity) and adaptive (e.g. T and B cell function) immune system exhibit suppressed function. Although such responses to football training and competition do not appear to be as pronounced, variations in immune cell numbers and function are reported in professional footballers over the course of a season. Attempts have been made through nutritional means (e.g. glutamine, vitamins C and E, and carbohydrate supplementation) to attenuate immune changes following intensive exercise and thus lower the risk of upper respiratory tract infection. Carbohydrate supplementation during heavy exercise has emerged as a partial countermeasure and attenuates increases in blood neutrophil counts, stress hormones, and inflammatory cytokines, but has little effect on decrements in salivary IgA output or natural killer cell function. Animal research indicates that other nutritional components such as beta-glucan, quercetin, and curcumin warrant human investigations to determine if they are effective countermeasures to exercise-induced immune dysfunction.

Dietary supplements for football

Physical training and competition in football markedly increase the need for macro- and micronutrient intake. This requirement can generally be met by dietary management without the need for dietary supplements. In fact, the efficacy of most supplements available on the market is unproven. In addition, players must be cautious of inadequate product labelling and supplement impurities that may cause a positive drug test. Nonetheless, a number of dietary supplements may beneficially affect football performance. A high endurance capacity is a prerequisite for optimal match performance, particularly if extra time is played. In this context, the potential of low-dose caffeine ingestion (2 - 5 mg . kg body mass(-1)) to enhance endurance performance is well established. However, in the case of football, care must be taken not to overdose because visual information processing might be impaired. Scoring and preventing goals as a rule requires production of high power output. Dietary creatine supplementation (loading dose: 15 - 20 g . day(-1), 4 - 5 days; maintenance dose: 2 - 5 g g . day(-1)) has been found to increase muscle power output, especially during intermittent sprint exercises. Furthermore, creatine intake can augment muscle adaptations to resistance training. Team success and performance also depend on player availability, and thus injury prevention and health maintenance. Glucosamine or chondroitin may be useful in the treatment of joint pain and osteoarthritis, but there is no evidence to support the view that the administration of these supplements will be preventative. Ephedra-containing weight-loss cocktails should certainly be avoided due to reported adverse health effects and positive doping outcomes. Finally, the efficacy of antioxidant or vitamin C intake in excess of the normal recommended dietary dose is equivocal. Responses to dietary supplements can vary substantially between individuals, and therefore the ingestion of any supplement must be assessed in training before being used in competition. It is recommended that dietary supplements are only used based on the advice of a qualified sports nutrition professional.

The roles of exercise-induced immune system disturbances in the pathology of heat stroke : the dual pathway model of heat stroke

Heat stroke is a life-threatening condition that can be fatal if not appropriately managed. Although heat stroke has been recognised as a medical condition for centuries, a universally accepted definition of heat stroke is lacking and the pathology of heat stroke is not fully understood. Information derived from autopsy reports and the clinical presentation of patients with heat stroke indicates that hyperthermia, septicaemia, central nervous system impairment and cardiovascular failure play important roles in the pathology of heat stroke. The current models of heat stroke advocate that heat stroke is triggered by hyperthermia but is driven by endotoxaemia. Endotoxaemia triggers the systemic inflammatory response, which can lead to systemic coagulation and haemorrhage, necrosis, cell death and multi-organ failure. However, the current heat stroke models cannot fully explain the discrepancies in high core temperature (Tc) as a trigger of heat stroke within and between individuals. Research on the concept of critical Tc as a limitation to endurance exercise implies that a high Tc may function as a signal to trigger the protective mechanisms against heat stroke. Athletes undergoing a period of intense training are subjected to a variety of immune and gastrointestinal (GI) disturbances. The immune disturbances include the suppression of immune cells and their functions, suppression of cell-mediated immunity, translocation of lipopolysaccharide (LPS), suppression of anti-LPS antibodies, increased macrophage activity due to muscle tissue damage, and increased concentration of circulating inflammatory and pyrogenic cytokines. Common symptoms of exercise-induced GI disturbances include diarrhoea, vomiting, gastrointestinal bleeding, and cramps, which may increase gut-related LPS translocation. This article discusses the current evidence that supports the argument that these exercise-induced immune and GI disturbances may contribute to the development of endotoxaemia and heat stroke. When endotoxaemia can be tolerated or prevented, continuing exercise and heat exposure will elevate Tc to a higher level (>42 degrees C), where heat stroke may occur through the direct thermal effects of heat on organ tissues and cells. We also discuss the evidence suggesting that heat stroke may occur through endotoxaemia (heat sepsis), the primary pathway of heat stroke, or hyperthermia, the secondary pathway of heat stroke. The existence of these two pathways of heat stroke and the contribution of exercise-induced immune and GI disturbances in the primary pathway of heat stroke are illustrated in the dual pathway model of heat stroke. This model of heat stroke suggests that prolonged intense exercise suppresses anti-LPS mechanisms, and promotes inflammatory and pyrogenic activities in the pathway of heat stroke.

Exercising in Environmental Extremes

Athletes, military personnel, fire fighters, mountaineers and astronauts may be required to perform in environmental extremes (e.g. heat, cold, high altitude and microgravity). Exercising in hot versus thermoneutral conditions (where core temperature is > or = 1 degrees C higher in hot conditions) augments circulating stress hormones, catecholamines and cytokines with associated increases in circulating leukocytes. Studies that have clamped the rise in core temperature during exercise (by exercising in cool water) demonstrate a large contribution of the rise in core temperature in the leukocytosis and cytokinaemia of exercise. However, with the exception of lowered stimulated lymphocyte responses after exercise in the heat, and in exertional heat illness patients (core temperature > 40 degrees C), recent laboratory studies show a limited effect of exercise in the heat on neutrophil function, monocyte function, natural killer cell activity and mucosal immunity. Therefore, most of the available evidence does not support the contention that exercising in the heat poses a greater threat to immune function (vs thermoneutral conditions). From a critical standpoint, due to ethical committee restrictions, most laboratory studies have evoked modest core temperature responses (< 39 degrees C). Given that core temperature during exercise in the field often exceeds levels associated with fever and hyperthermia (approximately 39.5 degrees C) field studies may provide an opportunity to determine the effects of severe heat stress on immunity. Field studies may also provide insight into the possible involvement of immune modulation in the aetiology of exertional heat stroke (core temperature > 40.6 degrees C) and identify the effects of acclimatisation on neuroendocrine and immune responses to exercise-heat stress. Laboratory studies can provide useful information by, for example, applying the thermal clamp model to examine the involvement of the rise in core temperature in the functional immune modifications associated with prolonged exercise. Studies investigating the effects of cold, high altitude and microgravity on immunity and infection incidence are often hindered by extraneous stressors (e.g. isolation). Nevertheless, the available evidence does not support the popular belief that short- or long-term cold exposure, with or without exercise, suppresses immunity and increases infection incidence. In fact, controlled laboratory studies indicate immuno-stimulatory effects of cold exposure. Although some evidence shows that ascent to high altitude increases infection incidence, clear conclusions are difficult to make because of some overlap with the symptoms of acute mountain sickness. Studies have reported suppressed cell-mediated immunity in mountaineers at high altitude and in astronauts after re-entering the normal gravity environment; however, the impact of this finding on resistance to infection remains unclear.

Dietary supplements and sports performance: amino acids

This is the third in a series of six articles to discuss the major classes of dietary supplements (vitamins; minerals; amino acids; herbs or botanicals; metabolites, constituents/extracts, or combinations). The major focus is on efficacy of such dietary supplements to enhance exercise or sport performance.

Comportamento de variáveis fisiológicas em atletas de nado sincronizado durante uma sessão de treinamento na fase de preparação para as Olimpíadas de Atenas 2004

O objetivo do presente estudo foi avaliar o comportamento de variáveis fisiológicas durante uma sessão de treino de nado sincronizado realizada na fase de preparação para as Olimpíadas de Atenas 2004. MATERIAIS E MÉTODOS: A amostra utilizada foi constituída pelo dueto (24 ± 0 anos) representante do Brasil em Atenas 2004. A coleta de dados foi realizada durante uma sessão de treinamento com duração de 198 minutos. O treino se iniciou com a parte física, seguida da parte técnica. Para a determinação da glicemia e da concentração de beta-hidroxibutirato foi utilizado o monitor Optium® com suas respectivas tiras. As concentrações de cortisol e das enzimas lactato desidrogenase (LDH) e creatina quinase (CK) foram determinadas por radioimunoensaio (DPC©) e kits comerciais (CELM®), respectivamente. O acompanhamento da freqüência cardíaca (FC) foi realizado com o freqüêncimetro Advantage Polar®. RESULTADOS: Foi observada redução (~2%) do peso corporal. A glicemia também apresentou queda (~30%) em comparação ao valor obtido no início do treino. Em contrapartida, foi observada elevação na concentração de cortisol (salivar 22% e plasmática 29%) e de beta-hidroxibutirato (~340%). Não foi observada alteração significativa na concentração plasmática de CK e de LDH. O acompanhamento da FC demonstrou que dos 198 minutos que constituíram a sessão de treino, 36,5 ± 0,7 minutos foram realizados em intensidade leve; 103,5 ± 0,7 minutos em intensidade moderada, 54,0 ± 2,1 minutos em intensidade alta e 4,0 ± 0,0 minutos em intensidade muito alta. CONCLUSÕES: A perda de peso indica que a reposição hídrica não foi adequada. A redução na glicemia e o aumento na concentração de corpos cetônicos e de cortisol reforçam a importância da suplementação de carboidrato durante o treino de longa duração. O comportamento da FC demonstra que a sessão de treinamento foi realizada em uma intensidade moderada, porém com breves momentos de intensidade alta, nos quais foram realizadas as rotinas.

Exercise immunology: the current state of man and mouse

The mechanisms governing the body's response to physical exercise have been investigated from various perspectives including metabolism, nutrition, age and sex. Increased attention to the immune system during recent decades is reflected by a rapidly growing number of publications in the field. This article highlights the most recent findings and only briefly summarises more basic concepts already reviewed by others. Topics include Th1/Th2 cytokine balance, inoculation time, age and immune compensation. Some less investigated areas are discussed including studies in children, the environment and dendritic cells. Because physical exercise enhances some aspects and suppresses other aspects of immunity, the biological significance of alterations in the immune system are unknown. So far, no link between immunological alterations and infection rate has been established and infection after strenuous physical exercise is equally likely to be the result of exercising with an already established rather than a new infection. If there is an increased risk for infections with increased exercise duration and intensity, why do overtrained athletes not display the greatest risk for upper respiratory tract infections? Increased knowledge on immune system modulations with physical exercise is relevant both from a public health and elite athlete's point of view.

Immune Status of Physically Active Women during Lactation

PURPOSE

The purpose of this study was to provide baseline data on immune status of exercising and sedentary exclusively lactating women. Dietary intake and body composition were also investigated to determine whether they related to immune function.

METHODS

Healthy, exclusively breastfeeding women with a body mass index between 20 and 30 kg x m were studied at 3 months postpartum. Participants in the exercise group (EG; N = 27) exercised aerobically at least 30 min x d, 3x wk, and women in the sedentary group (SG; N = 23) exercised once a week or less during the previous 6 wk. Immune status while at rest was determined by measuring: 1) a complete blood cell count and differential leukocyte count; 2) percentages and absolute counts of peripheral blood T cells (CD3+), cytotoxic T cells (CD3+CD8+), helper T cells (CD3+CD4+), B cells (CD19+), and natural killer cells (CD56+); 3) neutrophil bacterial killing and oxidative burst activity; and 4) in vitro mitogenic responsiveness of lymphocytes. Cardiorespiratory fitness, body composition, and dietary intake were also measured.

RESULTS

Participants in the EG had a significantly higher level of mean predicted cardiorespiratory fitness than women in the SG (39.5 +/- 1.1 vs 32.5 +/- 1.0 mL O2 x min x kg; P < 0.05); however, there were no significant differences in body composition or dietary intake. There were no significant differences in any of the indicators of immune status between groups. In addition, there were no significant relationships between body composition or dietary intake and immune status.

CONCLUSIONS

The results of this study suggest that women may exercise moderately during lactation and increase their fitness level without impairing their immune function.

ISSN Exercise & Sport Nutrition Review: Research & Recommendations

Sport nutrition is a constantly evolving field with literally thousands of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper presents a well-referenced overview of the current state of the science related to how to optimize training through nutrition. More specifically, this article discusses: 1.) how to evaluate the scientific merit of nutritional supplements; 2.) general nutritional strategies to optimize performance and enhance recovery; and, 3.) our current understanding of the available science behind weight gain, weight loss, and performance enhancement supplements. Our hope is that ISSN members find this review useful in their daily practice and consultation with their clients.

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.

Effect of exercise on immunologic factors in breast milk

OBJECTIVE

Although it is well documented that breast milk provides optimal nutrition and immune benefits to the infant, factors that influence the immunologic composition of breast milk are less understood. A recent study reported that immunoglobulin A (IgA) levels in breast milk are lower after exercise compared with resting concentrations. However, the women exercised until exhaustion. The effect of moderate exercise on immunologic components in breast milk has not been reported. Therefore, the purpose of this study was to 1) compare the levels of immunologic compounds in breast milk of exercising women with the milk of sedentary women and 2) determine whether 30 minutes of moderate exercise affects immunologic properties of breast milk.

METHODS

Exclusively lactating women were studied at 3 months' postpartum. Women in the exercise group (EG; n = 29) reported exercising aerobically at least 30 minutes/d for 3 days/wk, and women in the sedentary group (SG; n = 24) had exercised once a week or less during the previous 6 weeks. Cardiovascular fitness levels and concentrations of IgA, lactoferrin, and lysozyme in milk were measured. A subsample of the EG (n = 17) participated in a 30-minute exercise session at 75% of maximum heart rate and a rest session of 30 minutes of sitting rest on 2 separate days. Breast milk samples were collected before and 10 and 60 minutes after exercise and rest sessions. IgA, lactoferrin, and lysozyme concentrations were measured.

RESULTS

Women in the EG had a higher level of cardiovascular fitness than women in the SG (39.7 +/- 1.0 vs 32.4 +/- 1.0 mL O(2)/kg/min). Milk concentrations of IgA, lactoferrin, or lysozyme were not significantly different between groups. In addition, there were no significant differences in the concentrations of IgA, lactoferrin, or lysozyme after moderate exercise compared with sitting rest.

CONCLUSION

Moderate exercise during lactation improves cardiovascular fitness without affecting levels of IgA, lactoferrin, or lysozyme in breast milk.