Regulation of human skeletal muscle phosphorylase and glycogenolysis during maximal exercise

In six subjects, the transformation of phosphorylase and glycogenolytic rate were studied in the first and third of three 30-s bouts of maximal cycling, separated by 4 min of rest. Vastus biopsies were taken before, at 15s and 30s of bouts 1 and 3. In bout 1, the mole fraction of active phosphorylase (PHOS a) was 9.9+2.2% at rest, increased to 47.4±6.4% at 15s and by 30s, decreased to 21.8+4.2%. During the first and last 15s of bout 1, …