title: Glycogen depletion of human skeletal muscle fibers in response to high-frequency electrical stimulation.
abstract: The purpose of the present study was to evaluate the pattern of change in muscular glycogen content in response to high-frequency electrical stimulation (HFES). Muscle biopsies were taken from the vastus lateralis muscle of 7 healthy young men before, 15 min after, and 30 min after electrical stimulation delivered at a 50-Hz frequency (15 s on, 45 s off) at an intensity of 100 mA. The glycogen content of type I, IIA, and IIB muscle fibres was evaluated using microphotometry of periodic acid Schiff (PAS) stained fibres. After 15 min of electrical stimulation, the glycogen content in type I, IIA, and IIB muscle fibres significantly decreased from 113 +/- 10 (mean +/- SE) to 103 +/- 10 (p < or = 0.05), 129 +/- 9 to 102 +/- 12 (p < or = 0.01), and 118 +/- 8 to 90 +/- 13 (p < or = 0.01) arbitrary relative units, respectively. No further decrement in glycogen content was observed in all three fibre types following an additional 15 min of HFES. In addition, isometric force decreased by approximately 50%, from 125.9 +/- 20.0 N to 64.2 +/- 7.7 N (p < or = 0.01), during the first 15 contractions. No further decrease in isometric force was observed following an additional 15 contractions of HFES. These results reveal that significant reductions in isometric force of knee extensor muscles and glycogen content of all human skeletal muscle fibre types in vastus lateralis muscle are observable after 15 min of neuromuscular high-frequency transcutaneous electrical stimulation.
authors.affiliation: Dept. of Social and Preventive Medicine, Faculty of Medicine, Laval University, Ste-Foy Quebec, G1K 7P4.
authors.forename: Michel J
authors.initials: MJ
authors.lastname: Johnson
authors.forename: Gilles
authors.initials: G
authors.lastname: Lortie
authors.forename: Jean-Aimé
authors.initials: JA
authors.lastname: Simoneau
authors.forename: Marcel R
authors.initials: MR
authors.lastname: Boulay
mesh_terms: D004558:Electric Stimulation / Q000379:methods; D004734:Energy Metabolism; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007717:Knee / Q000502:physiology; D008297:Male; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D018657:Muscle Fibers, Slow-Twitch / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism*; D013848:Thigh; D013997:Time Factors
chemical_list: D006003:Glycogen