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Gender differences in force deficits after stretches of active rat skeletal muscles.
Willems MET; Stauber WT
Physiologist 2000 Aug; 43(4):358
Twenty stretches of plantar muscles, imposed on isometric contractions (80 Hz stimulation time 1.1 s, rest periods 3 min), were produced by dorsiflexion (a=3000 degrees s-2, ankle position 90 degrees to 40 degrees) in weight-matched anaesthetized female (F, n=6, bw 273 +/- 18 g, age 141 +/- 23 days, mean +/- SD) and male (M, n=6, bw 285 +/- 25 g, age 62 +/- 10 days) Sprague Dawley rats. Forces were measured at the plantar surface of the foot. Relative declines in isometric force at 90 degrees at 5, 10, 20, 40, 60, and 80 Hz before and after 1 hr of rest following the active stretches were measured. No gender differences were observed for isometric forces at each stimulation frequency before the stretch protocol. During the stretch protocol, the course of relative declines in isometric force and stretch force were similar for F and M rats. At the end of the stretch protocol, deficits in isometric force were 49.9 +/- 5.1% (F) and 45.9% +/- 5.3% (M) (P=0.2) and deficits in stretch force were 32.2 +/- 5.5% (F) and 35.0 +/0 4.4% (M) (P-0.4). One hour after the stretches, the remaining isometric force deficits at 5, 10, and 20 Hz were 18.6% (P<0.05) (F: 50.4 +/- 4.9%; M: 42.5 +/- 5.8%), 13.7% (P<0.05) (F: 51.0 +/- 4.3%; M 44.9 =/- 4.4%) and 16.3% (P<0.05) (F: 47.8 +/- 4.1%; M: 41.1 +/- 4.2%) larger for F than for M rats. In conclusion, the susceptibility of skeletal muscles to force deficits one hour following repeated active stretches is larger for 4 months old female rats than for male rats of comparable body weight.
Laboratory animals; Animals; Animal studies; Sex factors; Muscles; Skeletal system
Abstract; Conference/Symposia Proceedings
Issue of Publication
Disease and Injury: Musculoskeletal Disorders of the Upper Extremities
West Virginia University, Morgantown, West Virginia
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