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Metabolic characteristics of skeletal muscle during detraining from competitive swimming

COSTILL D. L.; FINK, W. J.; HARGREAVES, M.; KING, D. S.; THOMAS, R.; FIELDING, R.
Medicine & Science in Sports & Exercise: June 1985
ORIGINAL INVESTIGATIONS: PDF Only

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 μ1.h-1 · 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 < 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 < 0.05) for the trained swimmers (153 ± 3 mmol · kg-1) than for the untrained men (85 ± 7.5 mmol·kg-1). Over the 4 wk of inactivity, the swimmers' muscle glycogen progressively decreased from 153 (± 3) to 93 (±7) mmol·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·l-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.

©1985The American College of Sports Medicine