Changes in lymphocyte and neutrophil function induced by a marathon race

Recovery during Successive 120-min Football Games: Results from the 120-min Placebo/Carbohydrate Randomized Controlled Trial

PURPOSE

This study aimed to examine the recovery kinetics (i.e., time-dependent changes) of performance-related variables between two 120-min male football games performed 3 d apart with and without carbohydrate supplementation.

METHODS

Twenty male players (20 ± 1 yr; body fat, 14.9% ± 5.1%; maximal oxygen consumption, 59.4 ± 3.7 mL·kg -1 ·min -1 ) participated in two 120-min football games (G1, G2) according to a randomized, two-trial, repeated-measures, crossover, double-blind design. Participants received carbohydrate/placebo supplements during recovery between games. Field activity was monitored during the games. Performance testing and blood sampling were performed before and at 90 and 120 min of each game. Muscle biopsies were collected at baseline and at 90 and 120 min of G1 and pre-G2.

RESULTS

Compared with G1, G2 was associated with reduced total distance (10,870 vs 10,685 m during 90 min and 3327 vs 3089 m during extra 30 min; P = 0.007-0.038), average (6.7 vs 6.2 km/h during extra 30-min game-play; P = 0.007) and maximal speed (32.2 vs 30.2 km/h during 90 min and 29.0 vs 27.9 km/h during extra 30 min; P < 0.05), accelerations/decelerations ( P < 0.05), and mean heart rate ( P < 0.05). Repeated sprint ability ( P < 0.001), jumping ( P < 0.05), and strength ( P < 0.001) performance were compromised before and during G2. Muscle glycogen was not restored at G2 baseline ( P = 0.005). Extended game-play reduced lymphocyte, erythrocyte counts, hematocrit, hemoglobin, reduced glutathione ( P < 0.05) and increased delayed onset of muscle soreness, creatine kinase activity, blood glycerol, ammonia, and protein carbonyls ( P < 0.05) before and during G2. Pax7 + ( P = 0.004) and MyoD + cells ( P = 0.019) increased at baseline G2. Carbohydrate supplementation restored performance and glycogen, reduced glycerol and delayed onset of muscle soreness responses, and increased leukocyte counts and Pax7 + and MyoD + cells.

CONCLUSIONS

Results suggest that extended football games induce a prolonged recovery of performance, which may be facilitated by carbohydrate supplementation during a congested game fixture.

Hydrolyzed whey protein enriched with glutamine dipeptide attenuates skeletal muscle damage and improves physical exhaustion test performance in triathletes

Purpose

To investigate the effects of hydrolyzed whey protein enriched with glutamine dipeptide on the percentage of oxygen consumption, second ventilatory threshold, duration and total distance covered, and skeletal muscle damage during an exhaustion test in elite triathletes.

Methods

The study was a randomized, double-blinded, placebo-controlled, crossover trial. Nine male triathletes performed a progressive incremental test on a treadmill ergometer (1.4 km h^-1·3 min^-1) 30 min after ingesting either 50 g of maltodextrin plus four tablets of 700 mg hydrolyzed whey protein enriched with 175 mg of glutamine dipeptide diluted in 250 ml of water (MGln) or four tablets of 700 mg maltodextrin plus 50 g maltodextrin diluted in 250 ml of water (M). Each athlete was submitted to the two dietary treatments and two corresponding exhaustive physical tests with an interval of one week between the interventions. The effects of the two treatments were then compared within the same athlete. Maximal oxygen consumption, percentage of maximal oxygen consumption, second ventilatory threshold, and duration and total distance covered were measured during the exhaustion test. Blood was collected before and immediately after the test for the determination of plasma lactate dehydrogenase (LDH) and creatine kinase (CK) activities and lactate concentration (also measured 6, 10, and 15 min after the test). Plasma cytokines (IL-6, IL-1β, TNF-α, IL-8, IL-10, and IL-1ra) and C-reactive protein levels were also measured.

Results

A single dose of MGln increased the percentage of maximal oxygen consumption, second ventilatory threshold duration, and total distance covered during the exhaustion test and augmented plasma lactate levels 6 and 15 min after the test. MGln also decreased plasma LDH and CK activities indicating muscle damage protection. Plasma cytokine and C-reactive protein levels did not change across the study periods.

Conclusion

Conditions including overnight fasting and a single dose of MGln supplementation resulted in exercising at a higher percentage of maximal oxygen consumption, a higher second ventilatory threshold, blood lactate levels, and reductions in plasma markers of muscle damage during an exhaustion test in elite triathletes. These findings support oral glutamine supplementation's efficacy in triathletes, but further studies require.

Extracellular Inflammasome Particles Are Released After Marathon Running and Induce Proinflammatory Effects in Endothelial Cells

Objectives: The intracellular NLRP3 inflammasome is an important regulator of sterile inflammation. Recent data suggest that inflammasome particles can be released into circulation. The effects of exercise on circulating extracellular apoptosis-associated speck-like protein (ASC) particles and their effects on endothelial cells are not known.

Methods: We established a flow cytometric method to quantitate extracellular ASC specks in human serum. ASC specks were quantitated in 52 marathon runners 24–72 h before, immediately after, and again 24–58 h after the run. For mechanistic characterization, NLRP3 inflammasome particles were isolated from a stable mutant NLRP3 (p.D303N)-YFP HEK cell line and used to treat primary human coronary artery endothelial cells.

Results: Athletes showed a significant increase in serum concentration of circulating ASC specks immediately after the marathon (+52% compared with the baseline, p < 0.05) and a decrease during the follow-up after 24–58 h (12% reduction compared with immediately after the run, p < 0.01). Confocal microscopy revealed that human endothelial cells can internalize extracellular NLRP3 inflammasome particles. After internalization, endothelial cells showed an inflammatory response with a higher expression of the cell adhesion molecule ICAM1 (6.9-fold, p < 0.05) and increased adhesion of monocytes (1.5-fold, p < 0.05).

Conclusion: These findings identify extracellular inflammasome particles as novel systemic mediators of cell–cell communication that are transiently increased after acute extensive exercise with a high mechanical muscular load.

Changes in Cytokines Concentration Following Long-Distance Running: A Systematic Review and Meta-Analysis

Long-distance running is an exhausting effort for the whole organism. Prolonged aerobic exercise induces changes in inflammatory markers. However, predicting muscle damage in response has limitations in terms of selecting biomarkers used to measure inflammatory status. The present study conducts a systematic review and meta-analysis of articles focusing in ultra-marathon, marathon, and half-marathon and levels of cytokines. The search was conducted in PubMed, Web of Science, and Scopus databases, resulting in the inclusion of 76 articles. IL-6 was highlighted, evaluated in 62 studies and show increase in the standard mean difference (SMD): half-marathon (SMD −1.36; IC 95%: −1.82, −0.89, Ch²:0.58; tau²:0.00; p < 0.0001), marathon (SMD −6.81; IC 95%: −9.26, −4.37; Ch²:481.37 tau²:11.88; p < 0.0001) and ultra-marathon (SMD −8.00 IC 95%: −10.47, −5.53; Ch²:328.40; tau²:14.19; p < 0.0001). In contrast meta-regression analysis did not show relationship to the running distance (p = 0.864). The meta-analysis evidenced increase in the concentration of IL-1ra (p < 0.0001), IL-1B (p < 0.0001), IL-8 (p < 0.0001), IL-10 (p < 0.0001) and TNF-α (p < 0.0001). Reduction in IL-2 (p < 0.0001) and INF-y (p < 0.03) and no change in the IL-4 (p < 0.56). The number of studies evaluating the effect of adipokines was limited, however Leptin and Resistin were recurrent. The effects of an acute bout of prolonged aerobic exercise will protect against chronic systemic inflammation. The time to return to baseline values showed a substantial and dose-dependent relationship with run volume. The concentration of IL-6 was robustly studied and the marathon running was the most explored. Network of endocrine interactions in which circulating factors, released in extreme exercises, interplay through inter-organ crosstalk and physiologic changes were expressed. The running volume variability was able to modulate compounds that play a fundamental role in the maintenance of homeostasis and cell signaling.

Plasma Proteomic Changes of Atherosclerosis after Exercise in ApoE Knockout Mice

Atherosclerosis is the preliminary cause of coronary artery disease, one of the diseases that account for the largest number of fatal mortalities. Physical activity is an effective strategy to restrain atherosclerosis from deterioration. Evidence indicated that changes in the proteomic profile are highly associated with atherosclerosis development, but the mechanism behind exercise for atherosclerosis amelioration has not yet been investigated from a proteomics perspective. Hence, the proteomic profiles could further elucidate the systematic effects of exercise intervention on ApoE knockout atherosclerotic model and high-fat-diet intervention. In the current study, Apoeem1Narl/Narl mice were randomly allocated into a normal diet (ND), Western diet (WD), and WD with 12-week exercise intervention (WD EX) groups. The plasma proteome between WD and WD EX groups demonstrate the significant difference, and ten major pathways, including cardiovascular disease (CVD)–hematological disease, inflammatory disease, infectious diseases, inflammatory response, cell-to-cell signaling and interaction, connective tissue disorders_inflammatory disease, metabolic disease_organismal injury and abnormalities, cell-to-cell signaling and interaction, connective tissue disorders_inflammatory disease, and endocrine system disorders_gastrointestinal disease, etc., were generated by the IPA analysis. The 15 proteins (MYOCD, PROS1, C2, SERPINA10, CRP, F5, C5, CFB, FGG, CFH, F12, PRDX2, PROZ, PPIA, and HABP2) critically involved in CVD–hematological disease pathway showed significant difference between WD and WD EX groups. In current study, exercise could significantly alleviate the significantly elevated C5 and inflammation induced by the WD group in accordance with amelioration of atherosclerosis. Therefore, exercise could mitigate chemotaxis through the modulation of the C5 level and innate immunity, thereby alleviating the pathogenesis of atherosclerosis in Western-diet-induced obese mice.

Relationships between Vitamin D and Selected Cytokines and Hemogram Parameters in Professional Football Players-Pilot Study

Vitamin D affects both innate and adaptive immunity. Most of the effects of vitamin D on innate immunity are anti-inflammatory. In monocytes/macrophages, vitamin D suppresses the production of the inflammatory cytokines TNF-alpha, IL-1beta, IL-6, and IL-8. Therefore, the aim of our study was to investigate the relationship between 25(OH)D concentration and selected cytokines—IL-6, TNF-α, and IL-1β, which are hemogram parameters for professional football players. We enrolled 41 Polish premier league soccer players. The mean age, career duration, and VO_2max were, respectively: 22.7 ± 5.3 years, 14.7 ± 4.5 years, and 55.8 ± 4.0 mL/kg/min. Serum levels of 25(OH)D were measured by electrochemiluminescence (ECLIA) using the Elecsys system (Roche, Switzerland). Serum levels of IL-6, IL-1β, and TNF-α were measured by ELISA (R&D Systems, Minneapolis). Blood count with smear was measured on a Sysmex XT-4000i analyzer (Sysmex Corporation, Japan). Our study showed decreased serum 25(OH)D levels in 78% of the professional players. We found a significant negative correlation between 25(OH)D levels and TNF-α and LYMPH (%). The results also demonstrated a statistically significant positive correlation between vitamin D levels and NEUTH (%), NEUTH (tys/µL), and EOS (tys/µL). Based on the results of our study, we concluded that football players from Poland are not protected against vitamin D insufficiency in winter months. Moreover, vitamin D deficiency may be associated with an increased pro-inflammatory risk in well-trained athletes.

Features of Neutrophils From Atopic and Non-Atopic Elite Endurance Runners

We collected peripheral blood from thirty-nine elite male endurance runners at rest (24 hours after the last exercise session) and used the Allergy Questionnaire for Athletes score and plasma specific IgE level to separate them into atopic and non-atopic athletes. Neutrophils obtained from atopic and non-atopic athletes were subsequently stimulated in vitro with fMLP (N-formyl-methionyl-leucyl-phenylalanine), LPS (lipopolysaccharide), or PMA (phorbol 12-myristate 13-acetate). Neutrophils from non-atopic runners responded appropriately to LPS, as evidenced by the production of pro (IL-8, TNF-α, and IL-6) and anti-inflammatory (IL-10) cytokines. Neutrophils from atopic elite runners exhibited lower responses to LPS stimulus as indicated by no increase in IL-1β, TNF-α, and IL-6 production. Neutrophils from non-atopic and atopic runners responded similarly to fMLP stimulation, indicating that migration function remained unaltered. Both groups were unresponsive to PMA induced reactive oxygen species (ROS) production. Training hours and training volume were not associated with neutrophil IgE receptor gene expression or any evaluated neutrophil function. Since non-atopic runners normally responded to LPS stimulation, the reduced neutrophil response to the stimuli was most likely due to the atopic state and not exercise training. The findings reported are of clinical relevance because atopic runners exhibit a constant decline in competition performance and are more susceptible to invading microorganisms.

Immune Response of Elite Enduro Racers to Laboratory and Racing Environments: The Influence of Training Impulse and Vibration

Introduction: Understanding the sport-specific immune response elicited during both training and competition is imperative to maximise athlete health and performance. Despite a growing population of professional enduro mountain bike athletes, little is known about the recovery of the immune system following enduro racing events. Methods: Nine international level elite enduro mountain bike athletes (age 24.3 ± 2.4 years, height 178.5 ± 8.7 cm, mass 76.5 ± 12.5 kg) completed a laboratory-based maximal exercise test (LAB) on a cycle ergometer and competed in an international mountain bike enduro race event (RACE). Blood samples were taken before, immediately after, and 1 h after LAB and before, 1 h after, and 17 h after RACE. Leukocyte subsets were enumerated using seven-colour flow cytometry. Lucia’s training impulse (LuTRIMP) and vibration exposure (VIB) were quantified during RACE. Results: Seven participants were included in the final analyses. There was a significant (p < 0.05) increase in neutrophil count alongside a reduction of cytotoxic lymphocyte cell subsets of both the innate (CD3⁻/CD56⁺ NK-cells and CD3⁻/CD56^dim NK-cells) and adaptive (CD8⁺/CD62L⁻/CD45RA⁻ T-cells and CD8⁺/CD27⁺/CD28⁻ T-cells) components of the immune system one hour after RACE. All cell counts returned to baseline values 17 h afterwards (p > 0.05). Cell subset redistribution from pre- to post-one-hour time points (%Δpre-post1h) in cell subsets with potent effector functions (Neutrophils, CD3⁻/CD56⁺ NK-cells, CD8⁺/CD62L⁻/CD45RA⁻ T-cells, CD8⁺/CD27⁺/CD28⁻ T-cells, and CD3⁻/CD56^dim/CD57⁻ NK-cells) was significantly greater at RACE than LAB (p < 0.05). VIB was shown to be a superior predictor of %Δpre-post1h CD4⁺ T-cells, CD4⁺ early T-cells, CD4⁺ naïve T-cells, and NK cells as compared with LuTRIMP on its own (ΔR² = 0.63 − 0.89, p < 0.05). Conclusions: The race event offers a greater challenge to the immune system than LAB, and potentially, whole body vibration is a key component of training load measurement in mountain bike applications.

Effect of Acute and Chronic Aerobic Exercise on Immunological Markers: A Systematic Review

Introduction: The effects of aerobic exercise on the immune system are not yet fully defined in the scientific literature. This fact demonstrates the need to investigate its influence on existing immunological markers by classifying and quantifying their acute and chronic effects. Objective: To investigate the effects of acute and chronic aerobic exercise on inflammatory markers of healthy adults. Methods: This study is a systematic review according to PRISMA recommendations. The following databases were searched: MEDLINE (via PubMed), Science Direct, Scopus, Web of Science, SciELO, Bireme and Cochrane Library, and article references. The last search was performed in March 2019. We included randomized controlled trials (RCTs) and non-randomized controlled trials (NRCTs) investigating the acute and chronic effects of aerobic exercise on immune markers in healthy male and female adults aged 20 to 45 years, without restrictions in language or year of publication. Two authors independently analyzed the studies by reading the titles, abstracts, and full texts. Risk of Study bias was analyzed using Cochrane's Risk of Bias Tool. Outcomes: We included 15 studies in this systematic review, 13 of which were acute intervention and 2 were chronic, with 296 participants, 196 men and 100 women all being healthy individuals. It was observed that the acute intervention promotes changes in most immunological markers, while the chronic intervention interferes with a smaller proportion, this being in lymphocyte subpopulations. In the evaluation of quality, it was found that most studies did not present a high risk of bias in the evaluated aspects, but an unclear related risk of bias was observed, requiring a more careful analysis. Conclusion: Thus, it can be concluded that the evidence indicates that acute and chronic interventions may modify most immune markers, but aspects such as gender, contraceptive pill use in women, physical capacity of the investigated individuals, environment, and type and intensity of the exercises may interfere with these markers as well as the data analysis. Therefore, this review suggests that further research is needed to contribute to the confirmation and estimation of results.

DAILY HEMATOLOGIC ASSESSMENT DURING A 230-KM MULTISTAGE ULTRAMARATHON

ABSTRACT Introduction: The popularity of ultra-endurance events is increasing worldwide. However, information about hematological parameters during repeated bouts of long-duration running, such as stages during a multi-stage ultramarathon (MSUM) is scarce. Objective: The purpose of the study was to monitor daily hematologic assessment in a 230-km multistage ultramarathon (MSUM) in hot environmental conditions. Methods: Eleven male and three female (n = 14) ultra-endurance runners entered this MSUM, which was conducted over five stages, covering a total distance of 230 km in hot ambient conditions. Peripheral blood samples were collected before and after each stage to determine leukocyte and erythrocytes parameters. Results: Multilevel modelling considering all measurement points showed an increase for whole blood leukocyte and granulocyte counts at five stages of the MSUM and for monocytes until Stage 3 of the race. For erythrocyte parameters, decreases across stages were observed in hemoglobin concentration and hematocrit responses when computing/considering all measurement points. Conclusions: The results indicate that MSUM in a hot environment leads to a greater impact on leukocyte population responses and platelet variation in the initial stages of the race. We suggest that athletes may have a decrease in immune function in the early stages of the MSUM, probably with some transient risk of infectious. Nevertheless, a physiological adaptation to physical exertion and heat mitigates these changes in the subsequent stages of MSUM. Level of Evidence III; Case-control study.

Acute and Chronic Effects of Endurance Running on Inflammatory Markers: A Systematic Review

In order to understand the effect of endurance running on inflammation, it is necessary to quantify the extent to which acute and chronic running affects inflammatory mediators. The aim of this study was to summarize the literature on the effects of endurance running on inflammation mediators. Electronic searches were conducted on PubMED and Science Direct with no limits of date and language of publication. Randomized controlled trials (RCTs) and non-randomized controlled trials (NRCTs) investigating the acute and chronic effects of running on inflammation markers in runners were reviewed by two researchers for eligibility. The modified Downs and Black checklist for the assesssments of the methodological quality of studies was subsequently used. Fifty-one studies were finally included. There were no studies with elite athletes. Only two studies were chronic interventions. Results revealed that acute and chronic endurance running may affect anti- and pro-inflammatory markers but methodological differences between studies do not allow comparisons or generalization of the results. The information provided in this systematic review would help practitioners for better designing further studies while providing reference values for a better understanding of inflammatory responses after different running events. Further longitudinal studies are needed to identify the influence of training load parameters on inflammatory markers in runners of different levels and training background.

T-cells and their cytokine production: The anti-inflammatory and immunosuppressive effects of strenuous exercise

Strenuous exercise bouts and heavy training are associated with a heightened anti-inflammatory state and a transient suppression of several immune components. In turn, many athletes are susceptible to illness, particularly upper respiratory symptoms (e.g. cough, sore throat, running nose). T-lymphocytes (T-cells) are important for orchestrating the immune response and can be categorised into subsets according to their phenotypical characteristics resulting from polarisation (i.e. type-1, type-2 and regulatory T-cells). Each T-cell subset has a unique functional role, including their capacity to produce pro- and anti-inflammatory cytokines in response to an immune challenge. Prolonged and exhaustive exercise typically reduces peripheral blood type-1 T-cell number and their capacity to produce the pro-inflammatory cytokine, interferon-γ. Moreover, heavy training loads are associated with elevated numbers of resting peripheral blood type-2 and regulatory T-cells, which characteristically produce the anti-inflammatory cytokines, interleukin-4 and interleukin-10, respectively. This appears to increase the risk of upper respiratory symptoms, potentially due to the cross-regulatory effect of interleukin-4 on interferon-γ production and immunosuppressive action of IL-10. Catecholamines significantly influence the number of peripheral blood T-cells in response to exercise. Whereas, glucocorticoids and prostaglandin E2 promote the production of anti-inflammatory cytokines by T-cells. In summary, strenuous exercise bouts and heavy training shifts T-cell immunity towards an anti-inflammatory state. This impairs the ability of the immune system to mount an inflammatory response to an immune challenge, which may weaken defences against intracellular pathogens (e.g. viruses), and increase the risk of infection and viral reactivation.

Leukocyte Populations are Associated with Heart Rate Variability After a Triathlon

The purpose of this study was to analyze cellular immune components and their association with heart rate variability in triathlon athletes. Twelve athletes were included (age 36.41 ± 5.57 years, body mass 81.84 ± 10.97 kg) and blood samples were taken one week before, immediately, at 2 and 48 hours, and one week after competition. Total lymphocytes and their subpopulations, neutrophils, basophils, eosinophils and monocytes were analyzed. At the same time, heart rate variability was recorded for 30 minutes using Polar Team2®. A significant difference between lymphocyte subpopulations and heart rate variability was found in the different study periods. A positive correlation was found between total lymphocytes and rMSSD (r = .736, p <0.05), CD3+ and rMSSD (r = .785, p <0.05), and CD4+ and rMSSD (r = .795, p < 0.05) at the end of the competition. After one week of competition, a negative correlation was found between eosinophils and MRR, SDNN, pNN50, and rMSSD (p <0.01); and basophils and MRR, SDNN, pNN50, and rMSSD (p <0.01); while a positive correlation was found between CD19+ (B cells) and pNN50 (r = .678, p <0.05). Our results suggest that it is possible to predict the effect of training with regard to the athlete's performance.

Non-professional marathon running: RAGE axis and ST2 family changes in relation to open-window effect, inflammation and renal function

Conflicting data exist on the relevance of marathon (M) and half marathon (HM) running for health. The number of non-professional athletes finishing M and HM events is steadily growing. In order to investigate molecular changes occurring in amateur athletes, we enrolled 70 non-professional runners finishing a single M (34) or HM (36) event at baseline, the finish line and during recovery, and 30 controls. The measurement of the Receptor for Advanced Glycation Endproducts, Interleukin 1 receptor antagonist, ST2 and cytokeratin 18 was combined with molecules measured during clinical routine. Results were analyzed in the light of blood cell analysis, lactate measurements, correction for changes in plasma volume and body composition assessments. There were intrinsic differences in body mass index, abdominal body fat percentage and training time between M and HM runners. C-reactive protein changes in M and HM runners. While soluble RAGE, AGEs and ST2 increased immediately after the race in HM runners, HMGB1 increased in HM and M after the race and declined to baseline after a recovery period. We give insights into the regulation of various molecules involved in physical stress reactions and their possible implications for the cardiovascular system or renal function.

Lymphocyte Redox Imbalance and Reduced Proliferation after a Single Session of High Intensity Interval Exercise

This study investigated whether an acute session of high-intensity interval training (HIIT) is sufficient to alter lymphocyte function and redox status. Sixteen young healthy men underwent a HIIT session on a cycloergometer, consisting of eight bouts of 1 min at 90-100% of peak power, with 75 seconds of active recovery at 30 W between bouts. Venous blood was collected before, immediately after, and 30 minutes after the HIIT session. In response to Staphylococcus aureus superantigen B (SEB) stimulation, lymphocyte proliferation decreased and the IL-2 concentration increased after the HIIT session. However, the HIIT session had no effect on lymphocyte proliferation or IL-2 response to phytohemagglutinin stimulation. The HIIT session also induced lymphocyte redox imbalance, characterized by an increase in the concentration of thiobarbituric acid reactive substances and a decrease in the activity of the antioxidant enzyme catalase. Lymphocyte viability was not affected by the HIIT session. The frequencies of CD25+ and CD69+ T helper and B lymphocytes in response to superantigen stimulation were lower after exercise, suggesting that superantigen-induced lymphocyte activation was reduced by HIIT. However, HIIT also led to a reduction in the frequency of CD4+ and CD19+ cells, so the frequencies of CD25+ and CD69+ cells within the CD4 and CD19 cell populations were not affected by HIIT. These data indicate that the reduced lymphocyte proliferation observed after HIIT is not due to reduced early lymphocyte activation by superantigen. Our findings show that an acute HIIT session promotes lymphocyte redox imbalance and reduces lymphocyte proliferation in response to superantigenic, but not to mitogenic stimulation. This observation cannot be explained by alteration of the early lymphocyte activation response to superantigen. The manner in which lymphocyte function modulation by an acute HIIT session can affect individual immunity and susceptibility to infection is important and requires further investigation.