Effects of intermittent ischemia on contractile properties and myosin isoforms of skeletal muscle.
OBJECTIVE
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 approximately 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.
Dodd
S L
SL
Department of Exercise and Sports Sciences, University of Florida, Gainesville, USA.
Vrabas
I S
IS
Stetson
D S
DS
D000818:Animals; D001835:Body Weight; D007511:Ischemia / Q000503:physiopathology*; D008297:Male; D018908:Muscle Weakness / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000737:chemistry; D018995:Myosin Heavy Chains / Q000032:analysis*; D010805:Physical Conditioning, Animal; D051381:Rats; D017207:Rats, Sprague-Dawley
D018995:Myosin Heavy Chains