Glycogen storage, mobilization, and regulation in skeletal muscle metabolism during exercise enzymatic control and hormonal modulation

Abstract

Skeletal muscle glycogen represents the primary endogenous carbohydrate reservoir supporting physical activity. This research investigated the enzymatic mechanisms governing glycogen storage and mobilization during exercise, with particular emphasis on hormonal regulation patterns. Twenty-four trained male athletes participated in graded exercise protocols at the Exercise Physiology Laboratory, Lyon Institute of Biomedical Sciences, between March 2023 and September 2023. Muscle biopsies from the vastus lateralis were obtained at rest and during exercise at 30%, 60%, and 85% of maximal oxygen consumption. Glycogen phosphorylase activity increased from 12.4 ± 2.1 μmol/min/g protein at rest to 68.9 ± 5.2 μmol/min/g at high intensity, representing a 455% elevation. Conversely, glycogen synthase activity declined from 45.2 ± 3.8 μmol/min/g at rest to 11.7 ± 1.5 μmol/min/g during intense exercise. Plasma epinephrine concentrations correlated strongly with phosphorylase activation (r = 0.87, p