The purpose of this study was to evaluate the effects of ovariectomy on intramuscular energy metabolism in young rats. Twenty-four Sprague-Dawley rats (7 weeks old) were used. Twelve of them underwent ovariectomy (OVX), and the others were sham-operated on. Seven OVX rats were examined 1-week after surgery (OVX-1 group), and the other five, 4 weeks after surgery (OVX-4 group). The gastrocnemius-plantaris-soleus (GPS) muscles group was subjected to the following measurements, and the data were compared with those of the sham group (Sham-1: n = 7, or Sham-4 group: n = 5). From the 31P-MR spectra of the GPS muscles group at rest and during electric stimulation, the muscular oxidative capacity was measured. Maximum tension and wet weight of the whole GPS muscles group were also measured. Body weight in the OVX-4 group was significantly (p < 0.01) larger than that in the Sham-4 group. The weights of the whole GPS muscles group in the Sham-1, Sham-4, OVX-1 and OVX-4 groups were 1.17, 1.51, 1.25 and 1.71 (g), respectively. The muscle weight in the OVX group tended to be greater than that in the Sham group (p < 0.10). The maximum tension and oxidative capacity did not differ significantly among the groups. These data indicated that in young rats, ovariectomy induced an increase in body and muscle weight, but did not affect the maximum tension nor oxidative capacity.