title: Glycogen degradation during isometric exercise at low contraction force.
abstract: The glycogen content was measured in biopsy sample of human vastus lateralis muscle during prolonged isometric contraction with low force generation. In the first experiment 15% of the maximum voluntary contraction force (MVC) was held for 10 min. Glycogen utilization was 68.1 mmol glucosyl units.kg-1 dry muscle (d.m.). The study was continued by intermittent contractions of 50 s duration and 10 s rest repeated for 50 min. This resulted in a total glycogen utilization of 167.5 mmol glycosyl units.kg-1 d.m. The study was repeated with a force set of 7.5% MVC starting with 20 min continuous contraction followed by the same intermittent contractions for a further 100 min. The glycogen decrease was 15 mmol after the continuous contraction and totally 50 mmol after 2 h with the lower force. Thus the glycogen degradation rate even at low contraction force was related to the force level, being 6 times higher when the force was increased from 7.5 to 15% MVC. With prolonged isometric work periods at work loads corresponding to 15% MVC or higher depletion of the glycogen store can limit work performance capacity.
authors.affiliation: Department of Clinical Chemistry II, Huddinge University Hospital, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Hultman
authors.forename: K
authors.initials: K
authors.lastname: Söderlund
mesh_terms: D000328:Adult; D015444:Exercise; D005260:Female; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D009132:Muscles / Q000378:metabolism*
chemical_list: D006003:Glycogen