BACKGROUND: Numerous physiological responses occur due to changing energy demands induced by exercise training, including changes in substrate sensing and utilization in the gastrointestinal tractn and extracellular sensing to optimize substrate availability. The gut microbiota can contribute up to 10% of the host’s energy demand via short-chained fatty acid production and modulate intestinal permeability and signaling. The interaction between gut microbiota and exercise is poorly understood.
PURPOSE: Characterize the gut microbiota in collegiate swimmers whom undergo a sequentially reduced volume of training.
METHODS: Fecal samples, body composition (air displacement plethysmography) and training logs were collected from Division I NCAA collegiate swimmers for six consecutive weeks for 2016 (n = 9) and 2017 (n = 7), starting just before the taper and proceeding into the off-season. The fecal microbiota was characterized with shotgun metagenomics sequencing followed by multivariate statistical analysis using Qiime v1.9.1 and R programming language. Permutational ANOVAs, supervised learning and Bayesian modeling was used to determine significance (p < 0.05) of host-microbe interactions.
RESULTS: Systematic reduction in practice volume from Phase 1 (mean = 23.7 km/wk) to Phase 3 (mean = 13.9 km/wk) did not show any significant shifts in body composition (p > 0.05). Yet the microbial community showed a moderate but significant shift in structure (Adonis, p < 0.05, R = 0.154) and predicted function (Adonis, p < 0.05, R = 0.352). During high levels of practice volume, swimmers were dominated by the Clostridiales order of Firmicutes. Despite interpersonal variation in community composition, its temporal shift was largely explained by Clostridium Cluster IV and XIVa, which are known short-chained fatty acid producers.
CONCLUSION: Acute reduction in exercise among collegiate athletes significantly shifts the sub-phylum of specific Clostridiales in gut microbiota, possibly due to reduced exercise volume or requisite alterations in the diet.