Effects of submaximal cycling and long-term endurance training on neutrophil phagocytic activity in middle aged men

Assessment of Fatigue and Recovery in Sport: Narrative Review

Fatigue is a phenomenon associated with decreases in both physical and cognitive performances and increases in injury occurrence. Competitive athletes are required to complete demanding training programs with high workloads to elicit the physiological and musculoskeletal adaptations plus skill acquisition necessary for performance. High workloads, especially sudden rapid increases in training loads, are associated with the occurrence of fatigue. At present, there is limited evidence elucidating the underlying mechanisms associating the fatigue generated by higher workloads and with an increase in injury risk. The multidimensional nature and manifestation of fatigue have led to differing definitions and dichotomies of the term. Consequently, a plethora of physiological, biochemical, psychological and performance markers have been proposed to measure fatigue and recovery. Those include self-reported scales, countermovement jump performance, heart rate variability, and saliva and serum biomarker analyses. The purpose of this review is to provide an overview of fatigue and recovery plus methods of assessments.

Lymphocyte and dendritic cell response to a period of intensified training in young healthy humans and rodents: A systematic review and meta-analysis

Background: Intensified training coupled with sufficient recovery is required to improve athletic performance. A stress-recovery imbalance can lead to negative states of overtraining. Hormonal alterations associated with intensified training, such as blunted cortisol, may impair the immune response. Cortisol promotes the maturation and migration of dendritic cells which subsequently stimulate the T cell response. However, there are currently no clear reliable biomarkers to highlight the overtraining syndrome. This systematic review and meta-analysis examined the effect of intensified training on immune cells. Outcomes from this could provide insight into whether these markers may be used as an indicator of negative states of overtraining. Methods: SPORTDiscus, PUBMED, Academic Search Complete, Scopus and Web of Science were searched until June 2022. Included articles reported on immune biomarkers relating to lymphocytes, dendritic cells, and cytokines before and after a period of intensified training, in humans and rodents, at rest and in response to exercise. Results: 164 full texts were screened for eligibility. Across 57 eligible studies, 16 immune biomarkers were assessed. 7 were assessed at rest and in response to a bout of exercise, and 9 assessed at rest only. Included lymphocyte markers were CD3⁺, CD4⁺ and CD8⁺ T cell count, NK cell count, NK Cytolytic activity, lymphocyte proliferation and CD4/CD8 ratio. Dendritic cell markers examined were CD80, CD86, and MHC II expression. Cytokines included IL-1β, IL-2, IL-10, TNF-α and IFN-γ. A period of intensified training significantly decreased resting total lymphocyte (d= -0.57, 95% CI -0.30) and CD8⁺ T cell counts (d= -0.37, 95% CI -0.04), and unstimulated plasma IL-1β levels (d= -0.63, 95% CI -0.17). Resting dendritic cell CD86 expression significantly increased (d = 2.18, 95% CI 4.07). All other biomarkers remained unchanged. Conclusion: Although some biomarkers alter after a period of intensified training, definitive immune biomarkers are limited. Specifically, due to low study numbers, further investigation into the dendritic cell response in human models is required.

Polymorphonuclear leucocyte phagocytic function, γδ T-lymphocytes and testosterone as separate stress-responsive markers of prolonged, high-intensity training programs

Excessive exercise with limited recovery may lead to detrimental states of overreaching or the overtraining syndrome. Chronic maladaptation in endocrine and immune mechanisms occur with the incidence of these states. Exercise-induced cortisol and testosterone responses have been proposed as biomarkers of overreaching, with blunted responses following intensified-training periods. Yet, limited information on the effects of overreaching in immunity is available. Healthy individuals completed a 30-min running protocol (the RPE_TP) before and after a 12-day intensified-training period. Blood and saliva were collected before, after and 30min after RPE_TP at pre-training and post-training. Plasma and salivary cortisol and testosterone, leucocyte proliferation and polymorphonuclear leucocyte phagocytic activity were examined. Plasma and salivary cortisol were acutely unaffected pre-training (-14% and 0%, p ​> ​0.05) and post-training (-14% and +46%, p ​> ​0.05). Comparing pre-training with post-training, blunted responses were observed in plasma testosterone (43%-19%, p ​< ​0.05) and salivary testosterone (55%-24%, p ​> ​0.05). No acute or resting changes in total leucocyte counts or most leucocyte subsets occurred pre-training or post-training. Yet, a 194% acute elevation in γδ T-lymphocyte number occurred pre-training (p ​< ​0.05), and average resting concentrations were 174% higher post-training. Baseline phagocytic activity was 47% lower post-training (p ​< ​0.05). Intensified training was detrimental, significantly reducing phagocytic activity. Testosterone blunted post-training, indicating an excessive training-related hypothalamic-pituitary gonadal dysfunction. The γδ T-lymphocytes sensitivity to exercise was noted, rendering it as a potential stress-responsive cellular marker. The usefulness of the RPE_TP to track the onset of overreaching is proposed.

Chronic exercise modulates the cellular immunity and its cannabinoid receptors expression

The impact of performing exercise on the immune system presents contrasting effects on health when performed at different intensities. In addition, the consequences of performing chronic exercise have not been sufficiently studied in contrast to the effects of acute bouts of exercise. The porpoise of this work was to determine the effect that a popular exercise regimen (chronic/moderate/aerobic exercise) has on the proportion of different immune cell subsets, their function and if it affects the cannabinoid system with potentially functional implications on the immune system. A marked increase in several immune cell subsets and their expression of cannabinoid receptors was expected, as well as an enhanced proliferative and cytotoxic activity by total splenocytes in exercised animals. For this study male Wistar rats performed treadmill running 5 times a week for a period of 10 weeks, at moderate intensity. Our results showed a significant decrease in lymphocyte subpopulations (CD4+, Tγδ, and CD45 RA+ cells) and an increase in the cannabinoid receptors expression in those same cell. Although functional assays did not reveal any variation in total immunoglobulin production or NK cells cytotoxic activity, proliferative capability of total splenocytes increased in trained rats. Our results further support the notion that exercise affects the immunological system and extends the description of underlying mechanisms mediating such effects. Altogether, our results contribute to the understanding of the benefits of exercise on the practitioner´s general health.

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.

Neutrophil and Monocyte Bactericidal Responses to 10 Weeks of Low-Volume High-Intensity Interval or Moderate-Intensity Continuous Training in Sedentary Adults

Neutrophils and monocytes are key components of the innate immune system that undergo age-associated declines in function. This study compared the impact of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on immune function in sedentary adults. Twenty-seven (43 ± 11 years) healthy sedentary adults were randomized into ten weeks of either a HIIT (>90% maximum heart rate) or MICT (70% maximum heart rate) group training program. Aerobic capacity (VO_2peak), neutrophil and monocyte bacterial phagocytosis and oxidative burst, cell surface receptor expression, and systemic inflammation were measured before and after the training. Total exercise time commitment was 57% less for HIIT compared to that for MICT while both significantly improved VO_2peak similarly. Neutrophil phagocytosis and oxidative burst and monocyte phagocytosis and percentage of monocytes producing an oxidative burst were improved by training similarly in both groups. Expression of monocyte but not neutrophil CD16, TLR2, and TLR4 was reduced by training similarly in both groups. No differences in systemic inflammation were observed for training; however, leptin was reduced in the MICT group only. With similar immune-enhancing effects for HIIT compared to those for MICT at 50% of the time commitment, our results support HIIT as a time efficient exercise option to improve neutrophil and monocyte function.

Excessive Exercise and Immunity: The J-Shaped Curve

Exercise modulates the innate and specific arms of the immune system with a marked intensity-dependent response. This response might be influenced by sex differences and other factors including age, nutrition status, and overall level of psychological stress.

Exercise immunology is the field that studies this area. In the 1990s, Dr. Nieman formulated the controversial “J-shaped hypothesis” to describe the relationship between exercise intensity and the risk of acquiring upper respiratory tract infections (URTI). This hypothesis suggests that moderate exercise has the ability to improve immune function above sedentary levels while high intensity exercise depresses the immune system. However, some methodological problems exist in studies of the J-curve which makes evidence more anecdotal than evidence-based regarding the role of moderate and intense exercise in the incidence of URTI. These limitations are presented in the chapter.

Probiotic cheese attenuates exercise-induced immune suppression in Wistar rats

Intense physical activity results in a substantial volume of stress and hence a significant probability of immunosuppression in athletes, with milk proteins being, perhaps, the most recommended protein supplements. Consumption of a probiotic cheese can attenuate immune suppression induced by exhausting exercise in rats. A popular Brazilian fresh cheese (Minas Frescal cheese) containing Lactobacillus acidophilus LA14 and Bifidobacterium longum BL05 was fed for 2wk to adult Wistar rats, which then were brought to exhaustion on the treadmill. Two hours after exhaustion, the rats were killed and material was collected for the determination of serum uric acid, total and high-density lipoprotein cholesterol fraction, total protein, triacylglycerols, aspartate aminotransferase, alanine aminotransferase, creatine kinase, and blood cell (monocyte, lymphocyte, neutrophil, and leukocyte) counts. Exercise was efficient in reducing lymphocyte counts, irrespective of the type of ingested cheese, but the decrease in the group fed the probiotic cheese was 22% compared with 48% in the animals fed regular cheese. Monocyte counts were unaltered in the rats fed probiotic cheese compared with a significant decrease in the rats fed the regular cheese. Most importantly, ingestion of the probiotic cheese resulted in a >100% increase in serum high-density lipoprotein cholesterol and a 50% decrease in triacylglycerols. We conclude that probiotic Minas Frescal cheese may be a viable alternative to enhance the immune system and could be used to prevent infections, particularly those related to the physical overexertion of athletes.

Effect of exercise on gene expression profile in unfractionated peripheral blood leukocytes

A 4-h bout of exercise induces immunomodulatory effects. Peripheral blood was withdrawn before, and at 4, 8 and 24h after the start of exercise. RNA from the unfractionated white blood cells was analyzed using Agilent human 44K microarray. The expression profiles were sorted into seven clusters based on their unique time-dependent kinetics. In a separate experiment, cell-specific markers were collected and compared among the members in each cluster. Two clusters were assigned as representing neutrophils, one as NK cells, and another mostly as T cells. Three clusters seemed to be mixtures of several cell types. Extension of this approach to other systems is discussed.

Markers to measure immunomodulation in human nutrition intervention studies

Normal functioning of the immune system is crucial to the health of man, and diet is one of the major exogenous factors modulating individual immunocompetence. Recently, nutrition research has focused on the role of foods or specific food components in enhancing immune system responsiveness to challenges and thereby improving health and reducing disease risks. Assessing diet-induced changes of immune function, however, requires a thorough methodological approach targeting a large spectrum of immune system parameters. Currently, no single marker is available to predict the outcome of a dietary intervention on the resistance to infection or to other immune system-related diseases. The present review summarises the immune function assays commonly used as markers in human intervention studies and evaluates their biological relevance (e.g. known correlation with clinically relevant endpoints), sensitivity (e.g. within- and between-subject variation), and practical feasibility. Based on these criteria markers were classified into three categories with high, medium or low suitability. Vaccine-specific serum antibody production, delayed-type hypersensitivity response, vaccine-specific or total secretory IgA in saliva and the response to attenuated pathogens, were classified as markers with high suitability. Markers with medium suitability include natural killer cell cytotoxicity, oxidative burst of phagocytes, lymphocyte proliferation and the cytokine pattern produced by activated immune cells. Since no single marker allows conclusions to be drawn about the modulation of the whole immune system, except for the clinical outcome of infection itself, combining markers with high and medium suitability is currently the best approach to measure immunomodulation in human nutrition intervention studies. It would be valuable to include several immune markers in addition to clinical outcome in future clinical trials in this area, as there is too little evidence that correlates markers with global health improvement.

Immune function in sport and exercise

Regular moderate exercise is associated with a reduced incidence of infection compared with a completely sedentary state. However, prolonged bouts of strenuous exercise cause a temporary depression of various aspects of immune function (e.g., neutrophil respiratory burst, lymphocyte proliferation, monocyte antigen presentation) that usually lasts approximately 3-24 h after exercise, depending on the intensity and duration of the exercise bout. Postexercise immune function dysfunction is most pronounced when the exercise is continuous, prolonged (>1.5 h), of moderate to high intensity (55-75% maximum O(2) uptake), and performed without food intake. Periods of intensified training (overreaching) lasting 1 wk or more may result in longer lasting immune dysfunction. 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, such as upper respiratory tract infection. However, this may be a small price to pay as the anti-inflammatory effects of exercise mediated through cytokines and/or downregulation of toll-like receptor expression are likely mediators of many of the long-term health benefits of regular exercise.

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.

The effects of carbohydrate supplementation during the second of two prolonged cycling bouts on immunoendocrine responses

The purpose of this study was to examine the effect of carbohydrate (CHO) feeding during the second of two 90-min cycling bouts (EX1 started at 09:00 and EX2 started at 13:30) at 60% VO2max on leucocyte redistribution, neutrophil degranulation and oxidative burst and plasma IL-6 and stress hormone responses. This study consisted of two trials, which were completed in a counterbalanced order and separated by at least 4 days. Subjects (n=9) consumed a lemon flavoured 10% w/v CHO (glucose) or placebo (PLA) beverage during EX2: 500 ml just before exercise and 250 ml every 20 min during exercise. Venous blood samples were taken 5 min before exercise, immediately post-exercise, and 18-h post-EX2 for both trials. The main findings of this study were that ingestion of CHO compared with PLA during EX2 better maintained plasma glucose concentration, blunted the responses of plasma adrenaline, ACTH, cortisol, GH and IL-6, and attenuated the leukocytosis and monocytosis, but had no effect on neutrophil degranulation and oxidative burst activity. Furthermore, the immunoendocrine disturbances induced by two bouts of prolonged exercise returned to resting values within 18 h. These findings suggest that ingestion of CHO compared with PLA during the second of two bouts of 90-min cycling at 60% VO2max better maintains plasma glucose, blunts hypothalamic-pituitary-adrenal activation, and attenuates leucocyte trafficking, but does not affect neutrophil function. Furthermore, the disturbances of immunoendocrine responses induced by two bouts of prolonged exercise on the same day recover within 18 h.

Norepinephrine as mediator in the stimulation of phagocytosis induced by moderate exercise

During intensive exercise the stimulation of phagocytosis is mediated by "stress hormones". During moderate exercise, however, such mediation is less clear. The influence of moderate exercise (45 min at 55% maximal oxygen uptake) on the phagocytic capacity of neutrophils was evaluated in sedentary men. The exercise stimulated phagocytosis of Candida albicans, and the stimulation was maintained for at least 24 h. The possible neuroendocrine mediators were then investigated. Stimulation of phagocytosis was found after incubating neutrophils from sedentary individuals, who were in a basal state, with plasma from exercised individuals. Immediately after exercise, there was a significant increase in the concentration of norepinephrine, but not of epinephrine or cortisol. Incubation of neutrophils with this post-exercise physiological concentration of norepinephrine also stimulated phagocytosis, and the effect was blocked by both propranolol and phentolamine. The norepinephrine-augmented phagocytosis was accompanied by an increase in intracellular levels of cAMP, but not of cGMP or calcium. In conclusion, moderate exercise performed by sedentary people stimulates the phagocytic capacity of neutrophils, and the stimulation lasts for at least 24 h. Norepinephrine mediates the stimulation, although other mechanisms could be involved during the recovery period.

Intermittent hypobaric hypoxia increases the ability of neutrophils to generate superoxide anion in humans

1. We investigated the effect of intermittent exposure to hypobaric hypoxia on the ability of neutrophils to generate.O2-. 2. Seven male volunteers were exposed intermittently to hypobaric hypoxia, equivalent to an altitude of 4500 m, for 7 successive days. Peripheral blood samples were collected before and after the 2 h course of hypobaric hypoxia on days 1 and 7 and neutrophils were subjected to a chemiluminescence assay for.O2- production. 3. On day 1, 2 h exposure to hypobaric hypoxia induced granulocytosis (P < 0.01), but the ability of neutrophils to generate.O2- was unchanged. 4. On day 7, such granulocytosis was not observed, suggesting acclimatization to hypobaric hypoxia. 5. The ability of neutrophils to generate.O2- was significantly increased on day 7 (P < 0.01), although there was no definite change in the mRNA expression of NADPH oxidase subunits in the cells. 6. The results suggest that the ability of neutrophils to generate.O2- may be gradually potentiated by intermittent exposure to hypobaric hypoxia, even after the number of neutrophils in peripheral blood stabilizes.

Biochemical and immunological markers of over-training

Athletes fail to perform to the best of their ability if they become infected, stale, sore or malnourished. Excessive training with insufficient recovery can lead to a debilitating syndrome in which performance and well being can be affected for months. Eliminating or minimizing these problems by providing advice and guidelines on training loads, recovery times, nutrition or pharmacological intervention and regular monitoring of athletes using an appropriate battery of markers can help prevent the development of an overtraining syndrome in athletes. The potential usefulness of objective physiological, biochemical and immunological markers of overtraining has received much attention in recent years. Practical markers would be ones that could be measured routinely in the laboratory and offered to athletes as part of their sports science and medical support. The identification of common factors among overtrained athletes in comparison with well-trained athletes not suffering from underperformance could permit appropriate intervention to prevent athletes from progressing to a more serious stage of the overtraining syndrome. To date, no single reliable objective marker of impending overtraining has been identified. Some lines of research do, however, show promise and are based on findings that overtrained athletes appear to exhibit an altered hormonal response to stress. For example, in response to a standardized bout (or repeated bouts) of high intensity exercise, overtrained athletes show a lower heart rate, blood lactate and plasma cortisol response. Several immune measures that can be obtained from a resting blood sample (e.g. the expression of specific cell surface proteins such as CD45RO+ on T-lymphocytes) also seem to offer some hope of identifying impending overtraining. If an athlete is suspected of suffering from overtraining syndrome, other measures will also required, if only to exclude other possible causes of underperformance including post-viral fatigue, glandular fever, clinical depression, poor diet, anaemia, asthma, allergies, thyroid disorders, myocarditis and other medical problems interfering with recovery.

Acute exercise effects on the immune system

PURPOSE

In recent years, health professionals have placed increased attention on the benefits of physical activity for maintaining health in the general population as well as regaining health in many disease states. Conversely, reports of apparent decreases in immune cell function after acute exercise are widespread in the literature. The purpose of this article is to evaluate critically the available data and currently employed methods, with the aim of establishing whether genuine or artefactual alterations of immune function are being reported. During and immediately after exercise, the total number of white blood cells in peripheral blood samples increases, such that the relative proportions of cell types within the leukocyte pool are altered. A number of important areas of discussion arise from these shifts in the number of circulating cells after exercise, not least of which is the artefactual effects they may have on currently employed assays of immune cell function. Recent advances in methodology are beginning to call into question the assumption that acute exercise has any genuine immunosuppressive effect.

CONCLUSION

At present, there is little evidence to suggest that the range of acute exercise intensities and durations recommended by ACSM has a major detrimental effect on the function of individual T- and B-lymphocytes, natural killer cells and neutrophils. Although individual cells may not be as adversely affected as previously supposed, it is unclear whether the numerical content of the circulating population is an important clinical consideration.

Effects of mode and carbohydrate on the granulocyte and monocyte response to intensive, prolonged exercise

The influence of exercise mode and 6% carbohydrate (C) vs. placebo (P) beverage ingestion on granulocyte and monocyte phagocytosis and oxidative burst activity (GMPOB) after prolonged and intensive exertion was measured in 10 triathletes. The triathletes acted as their own controls and ran or cycled for 2.5 h at approximately 75% maximal O2 uptake, ingesting C or P (4 total sessions, random order, with beverages administered in double-blind fashion). During the 2. 5-h exercise bouts, C or P (4 ml/kg) was ingested every 15 min. Five blood samples were collected (15 min before exercise, immediately after exercise, and 1.5, 3, and 6 h after exercise). The pattern of change over time for GMPOB was significantly different between C and P conditions (P </= 0.05), with postexercise values lower during the C trials. Little difference was measured between running and cycling modes. C relative to P ingestion (but not exercise mode) was associated with higher plasma levels of glucose and insulin, lower plasma levels of cortisol and growth hormone, and lower blood neutrophil and monocyte cell counts. These data indicate that C vs. P ingestion is associated with higher plasma glucose levels, an attenuated cortisol response, and lower GMPOB.