Changes in force by repeated stretches of skeletal muscle in young and old female Sprague Dawley rats.
We examined whether the decline in isometric force and peak stretch force during repeated stretches of activated plantar flexor muscles was larger in old (24 months, N=5) compared with young (4 months, N=5) female Sprague Dawley rats. Thirty stretches were imposed on isometric contractions (stimulation time 1.9 s, rest periods 180 s) by ankle rotation from 90 degrees to 40 degrees at 50 degrees x s(-1). Even though muscle weights were similar [2094 +/- 54 (young) vs 2033 +/- 73 mg (old) (mean +/- SE)], the isometric force (IF) at 90 degrees before stretch 1 and peak stretch force (PSF) at 40 degrees for stretch 1 were lower in old rats [18.9 +/- 0.5 vs 15.5 +/- 1.4 N (p=0.024) and 25.8 +/- 1.3 vs 20.5 +/- 0.9 N (p=0.017)]. After the stretches, the IF deficit was similar [38.5 +/- 3.0% (young) vs 39.8 +/- 3.4% (old)] and did not recover after 1 hour of rest [35.1+/- 4.1% (young) vs 36.9 +/- 4.3% (old)]. The decline in PSF was/also similar [36.0 +/- 5.2% (young) vs 26.6 +/- 1.8% (old)]. Skeletal muscles of 24-month-old female Sprague Dawley rats were weaker than 4-month-old rats but had similar susceptibility to develop IF deficits after stretches of activated muscles.
Willems
M E
ME
Department of Physiology, West Virginia University, Morgantown 26506-9229, USA.
Stauber
W T
WT
D000375:Aging / Q000502:physiology*; D000818:Animals; D005260:Female; D006614:Hindlimb; D007537:Isometric Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley