INFLUENCE OF MUSCLE GLYCOGEN DEPLETION ON THE RATE OF RESYNTHESIS

In an effort to determine what effect the degree of muscle glycogen depletion has on the rate of resynthesis, six male cyclists completed an exercise protocol that involved both one- and two-legged cycling. One leg completed 30 min of single-leg cycling, ten one-min sprints, and 30 min cycling with both legs. This resulted in a large degree of depletion (LD). The contralateral leg completed only 30 min of double-leg cycling and experienced a small amount of depletion (SD). Following the exercise, the subjects rested quietly for 6 h and were fed a 24% carbohydrate (CHO) solution every 20 min in order to achieve a CHO intake of 0.7 g.kg-1.h-1. Biopsies taken from the vastus lateralis muscle immediately after exercise revealed that the glycogen content of the LD leg decreased 93.9 (+/- 11.6) (+/- 11.6) mmol.kg-1 w.w., whereas the SD leg used 49.3 (+/- 5.7) mmol. kg-1 w.w. (P < 0.01). Subsequent biopsies taken at 2 and 6 h of recovery demonstrated that the rate of muscle glycogen resynthesis was significantly greater in the LD leg, averaging 8.8 (+/- 2.4) mmol.kg-1.h-1 w.w., while the SD leg restored glycogen at a rate of 3.0 (+/- 1.0) mmol.kg-1.h-1 w.w. (P < 0.05). Glycogen synthase activity, expressed as its activity ratio (I/D), was also greater (P < 0.01) in the LD leg both immediately after exercise (0.45 +/- 0.05 vs 0.24 +/- 0.04) and at 2 h of recovery (0.54 +/- 0.06 vs 0.27 +/- 0.06). At 6 h of recovery, glycogen synthase activity did not differ between the legs; however, both values were significantly elevated above the pre-exercise level (P < 0.05). It is concluded that the magnitude of glycogen depletion does influence the rate of muscle glycogen resynthesis during the early hours of post-exercise recovery.