Probiotic supplementation elicits favourable changes in muscle soreness and sleep quality in rugby players

Probiotic supplementation may offer team sport athletes a range of benefits beyond the immune and gastrointestinal systems. Objectives: To examine the effects of a probiotic formulation on perceptual markers of sleep quality and quantity, and muscle soreness, leg heaviness and motivation in elite rugby union athletes. Methods: A double-blind randomised controlled trial involving 19 elite male rugby athletes was conducted over 17 weeks encompassing both domestic and international competition. Psychometric variables and salivary biomarkers were assessed twice a week. Athletes were assigned either a daily probiotic (Ultrabiotic 60™) and Saccharomyces boulardii (during international competition) or a placebo. Associations between psychometric scores for perceptual and salivary biomarkers of sleep (melatonin) and inflammation C-reactive protein (CRP) were investigated. Results: Muscle soreness was ∼0.5 units lower (F(1, 343) = 42.646, p < 0.0001) and leg heaviness scores ∼0.7 units lower (F(1, 334) = 28.990, p < 0.0001) in the probiotic group compared to the placebo group. Across both groups, as self-reported muscle soreness scores and salivary CRP concentrations increased, sleep quantity, quality and motivation scores decreased. Conversely as muscle soreness scores and CRP decreased, sleep quantity and quality, and motivation scores improved. Conclusions: A long-term programme of probiotic supplementation in international-level rugby union players may yield favourable effects on self-reported muscle soreness and sleep quality associated with muscle soreness during training and competitions. © 2020 Sports Medicine Australia