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) mmol.kg-1 w.w., whereas the SD leg used 49.3 (+/- 5.7) mmol.kg-1 w.w. (P less than 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.h1 w.w, while the SD leg restored glycogen at a rate of 3.0 (+/- 1.0) mmol.kg-1.h-1 w.w. (P less than 0.05). Glycogen synthase activity, expressed as its activity ratio (I/D), was also greater (P less than 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).(ABSTRACT TRUNCATED AT 250 WORDS)