Sl. Dodd et al., EFFECTS OF INTERMITTENT ISCHEMIA ON CONTRACTILE PROPERTIES AND MYOSINISOFORMS OF SKELETAL-MUSCLE, Medicine and science in sports and exercise, 30(6), 1998, pp. 850-855
Purpose: This study determined the effects of intermittent ischemia on
the contractile properties, fatigue (T-f), and myosin heavy chain com
position (MHC) in the rat gastrocnemius-plantaris-soleus 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. Ex
ercise in the E and SE groups consisted of running on a treadmill simi
lar to 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 th
ose 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 (V-max) was lower in the SE group compa
red with that in all others (10-14%). T-f was less in the S group comp
ared with that in C and E (28 and 30%, respectively). Type IIx MHC inc
reased and type IIb decreased in gastrocnemius and plantaris muscles i
n SE compared with those in C. Conclusions: These data indicate that i
ntermittent ischemia caused a decrease in muscle mass, maximal force d
evelopment, and V-max, but had no effect on T-f. The decrease in V-max
may have been related to myosin alterations in the muscles.