title: Metabolic characteristics of skeletal muscle during detraining from competitive swimming.
abstract: After 5 months of intense training, eight male swimmers were studied during 4 wk of inactivity. Biopsy specimens from the deltoid muscle revealed that its respiratory capacity (QO2) decreased by 50% (5174 to 2559 microliter X h-1 X g-1) after 1 wk of inactivity. Subsequent weeks of detraining did not change the QO2. Although the trained swimmers' muscle phosphofructokinase and phosphorylase activities were significantly higher (P less than 0.05) than those from a group (N = 8) of untrained men, 4 wk of detraining had no effect on these enzyme activities. Mean (+/-SE) resting muscle glycogen concentrations were significantly higher (P less than 0.05) for the trained swimmers (153 +/- 3 mmol X kg-1) than for the untrained men (85 +/- 7.5 mmol X kg-1). Over the 4 wk of inactivity, the swimmers' muscle glycogen progressively decreased from 153 (+/- 3) to 93 (+/-7) mmol X kg-1. After a standard 183-m swim at 90% of the swimmer's best time for that distance, blood lactate rose from a mean of 4.2 (+/-0.8) at week 0 to 9.7 (+/-0.8) mmol X 1(-1) at week 4. These observations demonstrate dramatic changes in the metabolic characteristics of the swimmer's muscle with a 1-4-wk interruption in training.
authors.forename: D L
authors.initials: DL
authors.lastname: Costill
authors.forename: W J
authors.initials: WJ
authors.lastname: Fink
authors.forename: M
authors.initials: M
authors.lastname: Hargreaves
authors.forename: D S
authors.initials: DS
authors.lastname: King
authors.forename: R
authors.initials: R
authors.lastname: Thomas
authors.forename: R
authors.initials: R
authors.lastname: Fielding
mesh_terms: D000328:Adult; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D008297:Male; D009132:Muscles / Q000378:metabolism*; D010101:Oxygen Consumption; D010732:Phosphofructokinase-1 / Q000378:metabolism; D006005:Phosphorylases / Q000378:metabolism; D010806:Physical Education and Training; D013550:Swimming
chemical_list: D006003:Glycogen; D006005:Phosphorylases; D010732:Phosphofructokinase-1