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Gabriella Berwig Möller, Maria Júlia Vieira da Cunha Goulart, Bruna Bellincanta Nicoletto, Fernanda Donner Alves and Cláudia Dornelles Schneider

Probiotics are live microorganisms, usually lactic acid bacteria, that when administered in adequate amounts, bring health benefits to the host ( Rijkers et al., 2011 ). Their usage has widely increased, mainly as dietary supplements in capsules, powder or fermented milk ( Pyne et al., 2015

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Eric S. Rawson, Mary P. Miles and D. Enette Larson-Meyer

may help athletes to train and/or compete more effectively without performance impediments. These supplements include creatine monohydrate, beta-hydroxy beta-methylbutyrate (HMB), omega-3 fatty acids, vitamin D, probiotics, gelatin, and anti-inflammatory supplements such as curcumin or tart cherry

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Michael Gleeson, Nicolette C. Bishop, Marta Oliveira and Pedro Tauler

The purpose of this study was to examine the effects of a probiotic supplement during 4 mo of winter training in men and women engaged in endurance-based physical activities on incidence of upper respiratory-tract infections (URTIs) and immune markers. Eighty-four highly active individuals were randomized to probiotic (n = 42) or placebo (n = 42) groups and, under double-blind procedures, received probiotic (PRO: Lactobacillus casei Shirota [LcS]) or placebo (PLA) daily for 16 wk. Resting blood and saliva samples were collected at baseline and after 8 and 16 wk. Weekly training and illness logs were kept. Fifty-eight subjects completed the study (n = 32 PRO, n = 26 PLA). The proportion of subjects on PLA who experienced 1 or more weeks with URTI symptoms was 36% higher than those on PRO (PLA 0.90, PRO 0.66; p = .021). The number of URTI episodes was significantly higher (p < .01) in the PLA group (2.1 ± 1.2) than in the PRO group (1.2 ± 1.0). Severity and duration of symptoms were not significantly different between treatments. Saliva IgA concentration was higher on PRO than PLA, significant treatment effect F(1, 54) = 5.1, p = .03; this difference was not evident at baseline but was significant after 8 and 16 wk of supplementation. Regular ingestion of LcS appears to be beneficial in reducing the frequency of URTI in an athletic cohort, which may be related to better maintenance of saliva IgA levels during a winter period of training and competition.

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Riina A. Kekkonen, Tommi J. Vasankari, Timo Vuorimaa, Tari Haahtela, Ilkka Julkunen and Riitta Korpela

Heavy exercise is associated with an increased risk of upper respiratory tract infections. Strenuous exercise also causes gastrointestinal (GI) symptoms. In previous studies probiotics have reduced respiratory tract infections and GI symptoms in general populations including children, adults, and the elderly. These questions have not been studied in athletes before. The purpose of this study was to investigate the effect of probiotics on the number of healthy days, respiratory infections, and GI-symptom episodes in marathon runners in the summer. Marathon runners (N = 141) were recruited for a randomized, double-blind intervention study during which they received Lactobacillus rhamnosus GG (LGG) or placebo for a 3-mo training period. At the end of the training period the subjects took part in a marathon race, after which they were followed up for 2 wk. The mean number of healthy days was 79.0 in the LGG group and 73.4 in the placebo group (P = 0.82). There were no differences in the number of respiratory infections or GI-symptom episodes. The duration of GI-symptom episodes in the LGG group was 2.9 vs. 4.3 d in the placebo group during the training period (P = 0.35) and 1.0 vs. 2.3 d, respectively, during the 2 wk after the marathon (P = 0.046). LGG had no effect on the incidence of respiratory infections or GI-symptom episodes in marathon runners, but it seemed to shorten the duration of GI-symptom episodes.

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Michael Gleeson, Nicolette C. Bishop, Marta Oliveira, Tracey McCauley, Pedro Tauler and Claire Lawrence

The purpose of this study was to examine the effects of a probiotic supplement during 4 mo of spring training in men and women engaged in endurance-based physical activities on incidence of upper respiratory tract infections (URTI) and mucosal immune markers. Sixty-six highly active individuals were randomized to probiotic (n = 33) or placebo (n = 33) groups and, under double-blind procedures, received probiotic (PRO: Lactobacillus salivarius, 2 × 1010 bacterium colony-forming units) or placebo (PLA) daily for 16 wk. Resting blood and saliva samples were collected at baseline and after 8 and 16 wk. Weekly training and illness logs were kept. Fifty-four subjects completed the study (n = 27 PRO, n = 27 PLA). The proportion of subjects on PRO who experienced 1 or more wk with URTI symptoms was not different from that of those on PLA (PRO .58, PLA .59; p = .947). The number of URTI episodes was similar in the 2 groups (PRO 1.6 ± 0.3, PLA 1.4 ± 0.3; p = .710). Severity and duration of symptoms were not significantly different between treatments. Blood leukocyte, neutrophil, monocyte, and lymphocyte counts; saliva IgA; and lysozyme concentrations did not change over the course of the study and were not different on PRO compared with PLA. Regular ingestion of L. salivarius does not appear to be beneficial in reducing the frequency of URTI in an athletic cohort and does not affect blood leukocyte counts or levels of salivary antimicrobial proteins during a spring period of training and competition.

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Samantha K. Gill, Dean M. Allerton, Paula Ansley-Robson, Krystal Hemmings, Martin Cox and Ricardo J.S. Costa

The study aimed to determine if short-term high dose probiotic supplementation containing Lactobacillus casei (L.casei) attenuates the commonly reported exertional-heat stress (EHS) induced endotoxinaemia and cytokinaemia. Eight endurance trained male volunteers (mean± SD: age 26 ± 6 y, nude body mass 70.2 ± 8.8 kg, height 1.75 ± 0.05 m, VO2max 59 ± 5 ml·kg-1·min-1) completed a blinded randomized cross-over design, whereby oral ingestion of a commercially available probiotic beverage containing L.casei (volume equivalent for ×1011 colony forming units·day-1) (PRO) or placebo (PLA) was consumed for 7 consecutive days before exposure to EHS, which comprised of 2h running exercise at 60% VO2max in hot ambient conditions (34.0 °C and 32% RH). Blood samples were collected at baseline (7 days before EHS), pre-EHS, post-EHS (1 hr, 2 hr, 4 hr, and at 24 hr). Plasma samples were analyzed for gram-negative bacterial endotoxin, cytokine profile (IL-6, IL-1β, TNF-α, IFN-γ, IL-8, and IL-10) and plasma osmolality. Plasma osmolality did not differ between trials. Seven days of L.casei supplementation did not show significant changes in resting circulatory endotoxin concentration or plasma cytokine profile compared with PLA. A main effect of time was observed for IL-6, TNF-α, IL-10 and IL-8; whereby levels increased in response to EHS (p < .05). Relative to pre-EHS concentrations, higher plasma concentrations of endotoxin (p = .05), and a trend for higher plasma TNF-α concentration (p = .09) was observed on PRO compared with PLA throughout recovery. Short-term high dose supplementation of a probiotic beverage containing L.casei before EHS did not attenuate EHS induced endotoxaemia and cytokinaemia; nor is it more positively favorable over a placebo.

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Samantha Kirsty Gill, Ana Maria Teixeira, Fatima Rosado, Martin Cox and Ricardo Jose Soares Costa

The study aimed to determine whether high-dose probiotic supplementation containing Lactobacillus casei (L. casei) for 7 consecutive days enhances salivary antimicrobial protein (S-AMP) responses to exertional–heat stress (EHS). Eight endurance-trained male volunteers (age 26 ± 6 years, nude body mass 70.2 ± 8.8 kg, height 1.75 ± 0.05 m, VO2max 59 ± 5 ml·kg-1·min-1 [M ± SD]) completed a blinded randomized and counterbalanced crossover design. Oral supplementation of the probiotic beverage (PRO; L. casei × 1011 colony-forming units·day-1) or placebo (PLA) was consumed for 7 consecutive days before 2 hr running exercise at 60% VO2max in hot ambient conditions (34.0 °C and 32% RH). Body mass and unstimulated saliva and venous blood samples were collected at baseline (7 days before EHS), pre-EHS, post-EHS (1 hr, 2 hr, and 4 hr), and at 24 hr. Saliva samples were analyzed for salivary (S) IgA, α-amylase, lysozyme, and cortisol. Plasma samples were analyzed for plasma osmolality. Body mass and plasma osmolality did not differ between trials. Saliva flow rate remained relatively constant throughout the experimental design in PRO (overall M ± SD = 601 ± 284 μ1/min) and PLA (557 ± 296 μl/min). PRO did not induce significant changes in resting S-AMP responses compared with PLA (p > .05). Increases in S-IgA, S-α-amylase, and S-cortisol responses, but not S-lysozyme responses, were observed after EHS (p < .05). No main effects of trial or Time × Trial interaction were observed for S-AMP and S-cortisol responses. Supplementation of a probiotic beverage containing L. casei for 7 days before EHS does not provide any further oral–respiratory mucosal immune protection, with respect to S-AMP, over PLA.

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Takeshi Kokubo, Yuta Komano, Ryohei Tsuji, Daisuke Fujiwara, Toshio Fujii and Osamu Kanauchi

(muscle exhaustion) and modification to the central nerve system (central fatigue; Clark & Mach, 2016 ). Several probiotics improve immune function and decrease URTI symptoms in healthy adults ( Berggren et al., 2011 ; de Vrese et al., 2005 ); however, their potency, although promising in athletes

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David B. Pyne, Evert A. Verhagen and Margo Mountjoy

In this review, we outline key principles for prevention of injury and illness in aquatic sports, detail the epidemiology of injury and illness in aquatic athletes at major international competitions and in training, and examine the relevant scientific evidence on nutrients for reducing the risk of illness and injury. Aquatic athletes are encouraged to consume a well-planned diet with sufficient calories, macronutrients (particularly carbohydrate and protein), and micronutrients (particularly iron, zinc, and vitamins A, D, E, B6, and B12) to maintain health and performance. Ingesting carbohydrate via sports drinks, gels, or sports foods during prolonged training sessions is beneficial in maintaining energy availability. Studies of foods or supplements containing plant polyphenols and selected strains of probiotic species are promising, but further research is required. In terms of injury, intake of vitamin D, protein, and total caloric intake, in combination with treatment and resistance training, promotes recovery back to full health and training.

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David B. Pyne, Joshua H. Guy and Andrew M. Edwards

Heat and immune stress can affect athletes in a wide range of sports and environmental conditions. The classical thermoregulatory model of heat stress has been well characterized, as has a wide range of practical strategies largely centered on cooling and heat-acclimation training. In the last decade evidence has emerged of an inflammatory pathway that can also contribute to heat stress. Studies are now addressing the complex and dynamic interplay between hyperthermia, the coagulation cascade, and a systemic inflammatory response occurring after transient damage to the gastrointestinal tract. Damage to the intestinal mucosal membrane increases permeability, resulting in leakage of endotoxins into the circulation. Practical strategies that target both thermoregulatory and inflammatory causes of heat stress include precooling; short-term heat-acclimation training; nutritional countermeasures including hydration, energy replacement, and probiotic supplementation; pacing strategies during events; and postevent cooling measures. Cooperation between international, national, and local sporting organizations is required to ensure that heat-management policies and strategies are implemented effectively to promote athletes’ well-being and performance.