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Athletes appear to be at a greater risk of illness while undertaking arduous training regimens in preparation for endurance events. As infection susceptibility has been linked with increased proportions of differentiated and senescent T cells in the periphery, changes in the proportions of these cell types due to long-term high-volume exercise training could have important implications for athlete infection risk. This study examined the effects of 6-month training preparation for an Ironman triathlon on the proportions of naïve, memory and senescent T cells in resting blood. Ten club-level triathletes (9 males; 1 female: 43 ± 3 years) were sampled at 27 (December), 21 (January), 15 (March), 9 (May) and 3 (June) weeks before an Ironman Triathlon. An additional sample was collected 2-week post-competition (August). Four-colour flow cytometry was used for the phenotypic analysis of CD4+ and CD8+ blood T cells. Proportions of differentiated (KLRG1+/CD57-) CD8+ T cells and "transitional" (CD45RA+/CD45RO+) CD4+ and CD8+ T cells increased with training, as the values in June were elevated 37, 142 and 116%, respectively, from those observed in December. Proportions of senescent (KLRG1+/CD57+) CD4+ or CD8+ T cells did not change during the training phase. Two weeks post-race, proportions of differentiated CD8+ T cells had returned to baseline values, while the proportions of senescent CD4+ T cells increased 192% alongside a 31% reduction in naïve (CD45RA+/CD45RO-) cells. In conclusion, increases in differentiated and "transitional" T cells due to arduous exercise training could compromise host protection to novel pathogens and increase athlete infection risk, although whether or not the composition of naïve and differentiated T cells in blood can serve as prognostic biomarkers in athletes remains to be established. [ABSTRACT FROM AUTHOR]

The aim of the current study was to examine the effect of a moderate alteration in pre-exercise diet composition on the performance of, and metabolic response to, intermittent treadmill exercise in a group of normally menstruating females. Eight recreationally active women performed two intermittent, incremental exercise trials, one preceded by 2 days of a high [61 (1)%] carbohydrate (CHO) diet and the other by 2 days of a low [31 (1)%] CHO diet. Oxygen uptake (VO2) was measured during, and blood samples were obtained immediately after, each bout for the determination of blood lactate, glucose, glycerol, plasma free fatty acids and plasma ammonia. Performance, as assessed by time to exhaustion in the final bout, was found to be similar whether preceded by a high- or low-CHO diet [median (range): 28.0 (18-54) s, 29 (18-54) s, respectively]. No significant between trial differences were found in VO2, heart rate, or any of the blood metabolites. The results of the current, study indicate that moderate alterations of pre-exercise diet do not affect intermittent, high-intensity exercise performance in women, despite some evidence of an alteration in the pattern of the metabolic response to exercise.