title: Muscle glycogen utilization and the expression of relative exercise intensity.
abstract: Previous research has shown that the rate of muscle glycogen utilization is related to exercise intensity expressed relative to maximal aerobic power (%VO2max). The purpose of this study was to compare the relationship between glycogen utilization and %VO2max to that between glycogen utilization and intensity expressed relative to the onset of blood lactate accumulation (%OBLA) during cycle exercise. It was hypothesized that the rate of glycogen utilization would be related more closely to intensity expressed as %OBLA than to intensity expressed as %VO2max. Nineteen subjects (15 males and 4 females) performed two separate tests to determine VO2max and OBLA during continuous incremental exercise. On a third occasion biopsies were taken from the m. vastus lateralis before and after 30 min of exercise at randomly assigned intensities ranging from 50-80% VO2max, corresponding to 67-117% OBLA. There was a large inter-subject variation in aerobic fitness with VO2max ranging from 34 to 66 mL.kg-1.min-1 and OBLA ranging from 64-84% VO2max. Absolute VO2max and the VO2 at OBLA were correlated strongly (r = 0.90). The change in glycogen concentration during the 30-min exercise bout ranged from an increase of 58 to a depletion of 200 mmol glucose units.kg-1 dry muscle weight. Neither absolute nor relative glycogen utilization was significantly related to the exercise intensity expressed as either %VO2max or %OBLA. Stepwise multiple regression was used to identify variables which could account for the variation in glycogen depletion.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Biosciences Division, Defence and Civil Institute of Environmental Medicine, Downsview, Ontario, Canada.
authors.forename: T M
authors.initials: TM
authors.lastname: McLellan
authors.forename: I
authors.initials: I
authors.lastname: Jacobs
mesh_terms: D005260:Female; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D008297:Male; D009132:Muscles / Q000378:metabolism*; D010101:Oxygen Consumption; D010809:Physical Fitness / Q000502:physiology*; D012044:Regression Analysis; D012737:Sex Factors
chemical_list: D007773:Lactates; D019344:Lactic Acid; D006003:Glycogen