The effects of carbohydrate-protein supplementation on glycogen utilization and fatigue during a simulated soccer match

The purpose of this study was to examine if the addition of protein to a carbohydrate supplement (CHO+PRO), provided during a simulated soccer match, would reduce fatigue and muscle glycogen utilization in comparison to an isocaloric carbohydrate only supplement (CHO). Two female and eight male (n = 10) trained soccer players performed a modified version of the Loughborough Intermittent Shuttle Test (LIST) on two separate occasions, followed by a run to exhaustion (RTE). Supplements were provided 10 minutes before the simulated match and at the beginning of half-time, but not during exercise in order to create real-match conditions. Supplements were composed of 2.8% protein + 7% carbohydrate (CHO+PRO) or 9.8% carbohydrate (CHO). Muscle biopsies were performed before and at the end of the LIST, after which iv participants ran to exhaustion. No differences were found between treatments for RTE (489 ± 121 sec for CHO and 589 ± 186 sec for CHO+PRO) or glycogen utilization (37.9 ± 7.6 µmol•g wet wt-1 during the CHO and 29.1 ± 6.0 µmol•g wet wt-1 during the CHO+PRO). No differences were found for the other measurements such as sprint times, heart rate, RPE, blood glucose, lactate, and insulin. Blood Creatine kinase (CK), and overall muscle soreness were measured 24 hours after each trial in order to evaluate muscle damage but no differences between treatments were found. In accordance with these findings, the phosphorylation state of the protein FOXO3a was not altered differently by the treatments. These results suggest that the addition of protein to a traditional carbohydrate-only supplement provided immediately prior to and at the half of a simulated soccer match does not further improve the benefits of a CHO supplement.