Effects of intermittent ischemia on contractile properties and myosin isoforms of skeletal muscle. Med. Sci. Sports Exerc., Vol. 30, No. 6, pp. 850-855, 1998.
Purpose: This study determined the effects of intermittent ischemia on the contractile properties, fatigue (Tf), and myosin heavy chain composition (MHC) in the rat gastrocnemius-plantarissoleus muscle (GPS) complex.
Methods: Fifty rats were divided into four groups: control (C, N = 12), severed (femoral artery) (S, N = 12), exercise (E, N = 13), and severed/exercise (SE, N = 13). Ischemia was elicited only in the SE group by daily exercise and the other groups served as controls. Exercise in the E and SE groups consisted of running on a treadmill ∼ 35 min·d−1, 5 d·wk−1 for 7 wk.
Results: Body weight, muscle weight, and absolute force were less in the SE group compared with those in C (12, 18, and 12% respectively). However, relative force (N·g−1 of muscle) was greater in the SE group compared with that in C (8%). Maximal shortening velocity (Vmax) was lower in the SE group compared with that in all others (10-14%). Tf was less in the S group compared with that in C and E (28 and 30%, respectively). Type IIx MHC increased and type IIb decreased in gastrocnemius and plantaris muscles in SE compared with those in C.
Conclusions: These data indicate that intermittent ischemia caused a decrease in muscle mass, maximal force development, and Vmax, but had no effect on Tf. The decrease in Vmax may have been related to myosin alterations in the muscles.
Department of Exercise and Sports Sciences, University of Florida, Gainesville, FL
Submitted for publication April 1997.
Accepted for publication December 1997.
Address for correspondence: Stephen L. Dodd, Ph.D., Department of Exercise and Sports Sciences, #118 FLG, University of Florida, Gainesville, FL 32611.