Metabolic And Physiological Responses To 120 Minutes Of Soccer-Specific Exercise

The metabolic and physiological responses to 90 minutes of soccer-specific exercise have been extensively reported. However, the responses to an additional 30 minutes of play (termed extratime; ET) are unclear. This is surprising as performance during ET can determine progression in specific tournament matches. PURPOSE: To profile the metabolic and physiological responses to 120 minutes of simulated soccer match-play. METHODS: Following habituation of protocol-specific practices, 22 university standard soccer players (21 ± 2 y) completed 120 minutes of a soccer-specific protocol. Venous blood was collected during exercise for analysis of blood glucose and lactate, plasma insulin, epinephrine, interleukin-6 (IL-6) glycerol, non-esterified fatty acids (NEFA) and plasma volume changes. Heart rate (HR), rating of perceived exertion (RPE), and 15-m sprint velocities were measured throughout exercise. RESULTS: Repeated measures analysis of variance highlighted that exercise significantly influenced all measured variables (p<0.001). Blood glucose, lactate and plasma insulin concentrations were lower (p<0.05) in ET compared to all time points up to, and including 90 minutes (-11%, -15%, -15%, compared to 90 min, respectively). Plasma IL-6, epinephrine, glycerol and NEFA were higher (p<0.05) in ET compared to all time points up to and including 90 minutes (+28%, +110%, +26%, +34%, compared to 90 min, respectively). There were no significant changes in plasma volume or HR during ET compared to the rest of exercise. RPE was higher (p<0.001) during ET compared to the first 90 minutes of exercise (16±2 vs. 13±2). Sprint velocities (15-m) were lower during ET compared to the first 90 minutes of exercise (4.98 ± 0.29 vs. 5.43 ± 0.38 ms-1; p<0.001). CONCLUSIONS: The ET period elicits different physiological and metabolic responses to those observed during the prior 90 minutes of soccer-specific exercise. Reductions in blood glucose and lactate with concomitant increases in plasma epinephrine, NEFA and glycerol may demonstrate a greater reliance on fat oxidation and a likely greater dependency on endogenous fuel sources (i.e., muscle and liver glycogen). With reductions in exercise performance (i.e., reduced sprint velocities) and a greater physiological challenge (i.e., increased RPE), interventions that seek to attenuate diminutions in performance provide future research opportunities.