Abstract
We hypothesised that probiotic supplementation (PRO) increases the absorption and oxidation of orally ingested maltodextrin during 2h endurance cycling, thereby sparing muscle glycogen for a subsequent time trial (simulating a road race). Measurements were made of lipid and carbohydrate oxidation, plasma metabolites and insulin, gastrointestinal permeability, and subjective symptoms of discomfort. Seven male cyclists were randomized to PRO (bacterial composition given in methods) or placebo (PLC) for four weeks, separated by a 14-day washout period. After each period, cyclists consumed a 10% maltodextrin solution (initial 8 mL·kg-1 bolus and 2 mL·kg-1 every 15 min) while exercising for 2h at 55% Wmax followed by a 100 kJ time trial. PRO resulted in small increases in peak oxidation rates of the ingested maltodextrin (0.84 ± 0.10 vs 0.77 ± 0.09 g·min-1, P = 0.016), and mean total carbohydrate oxidation (2.20 ± 0.25 vs 1.87 ± 0.39 g·min-1, P = 0.038), while fat oxidation was reduced (0.40 ± 0.11 vs 0.55 ± 0.10 g·min-1, P = 0.021) . During PRO small but significant increases were seen in glucose absorption, plasma glucose and insulin concentration and decreases in NEFA and glycerol. Differences between markers of GI damage and permeability and time trial performance were not significant (P > 0.05). In contrast to the hypothesis, PRO led to minimal increases in absorption and oxidation of the ingested maltodextrin and small reductions in fat oxidation, while having no effect on subsequent time trial performance.