Skeletal Muscle Metabolism During Team-sport-specific Repeated High Intensity Intermittent Exercise In Trained Male Athletes

PURPOSE: Muscle metabolism during repeated high intensity exercise scenarios has been shown to be affected by exercise duration and previous exercise. However, muscle metabolism during team-sport-specific high intensity intermittent exercise has not been examined in relation to whether high-intensity exercise bouts occur early or late in a game. Therefore, we mimicked intense 5-min periods in a soccer game to investigate the muscle metabolic and fatigue responses to a peak intensity period occurring early and late in a game. METHODS: Trained male soccer athletes (n = 11) performed a modified simulated soccer game (the Copenhagen Soccer Test) with two 5-min peak-intensity period simulations consisting of repeated intense runs inserted early (PP1; 10-15 min) and late (PP2: 85-90 min) in the game-protocol. Muscle biopsies were obtained immediately prior and after each peak period. RESULTS: Muscle glycogen concentration was degraded by 62 ± 46 mmol·kg-1 d.w. (P < 0.001) during PP1 and only numerically by 25 ± 37 mmol·kg-1 d.w. during PP2 (P = 0.142). Muscle glycogen breakdown tended to be faster in PP1 vs. PP2 (P = 0.115). Muscle lactate accumulated to 47 ± 25 and 32 ± 12 mmol·kg-1 after PP1 and PP2, respectively (P < 0.001), with higher concentrations in PP1 compared to PP2 (P = 0.025). Muscle ATP concentrations declined by 3-5% during PP1 (P = 0.019) and PP2 (0.022), whereas phosphocreatine (PCr) levels were lowered by ~50% following both peak periods (P < 0.001). RPE was higher during PP2 (P < 0.001), while 10-m sprint performance declined by 10-11% during both peak periods (P < 0.001), with no differences in mean sprint time (P = 0.280). CONCLUSIONS: High intensity intermittent exercise occurring early in a team sport simulated game has a markedly different metabolism as compared to when repeated later in game, with larger muscle glycogen utilization and lactate accumulation early in a game. Both peak intense periods demonstrated a similar muscle ATP and PCr depletion. In contrast perceived exertion was higher late in the game. The Swedish Football Association