Exhaustive running: inappropriate as a stimulus of muscle glycogen super-compensation.

Muscle glycogen super-compensation, as demonstrated after exhaustive cycling, may be affected by mode of exercise and state of training. Hence, we studied the effect of exhaustive running on post-exercise changes in muscle glycogen concentration in untrained subjects and compared the effect of tapered running with an exhaustive bout of running in well-trained runners. Six trained runners (T), 6 untrained subjects (UT), and 6 physically active subjects participated. Four hundred grams of carbohydrate were given for 2 d (PX2 and PX1) before exercise and 600 g for 3 d (R1, R2, and R3) with rest afterwards. Before exercise, T and UT were restricted in physical activity. Biopsies were obtained from the gastrocnemius muscle on PX2 and PX1 in T, and before (PX0), immediately after exercise (R0), and on R1, R2, and R3 in all groups. Muscle glycogen increased from 110 (+/-14) on PX2 to 180 (+/-11) mmol X kg-1 on PX0 in T (P less than 0.001). This PX0 value was higher than the PX0 value for UT, which was 102 (+/-8) mmol X kg-1 (P less than 0.005). R0 values were 57 (+/-14) and 26 (+/-4) mmol X kg-1, respectively. On R1, the glycogen concentration had increased to 127 (+/-10) and 87 (+/-3) mmol X kg-1 (P less than 0.001). No changes occurred during R2 and R3. In a supplementary study, physically active subjects rested (series I) or ran lightly for 40 min (series II) on PX2 and PX1, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)