The purpose of this study was to evaluate the effects of ovariectomy on intramuscular energy metabolism in adult rats. Based on the results, we discussed the skeletal muscle metabolism in female athlete with sports related amenorrhea. Twenty-five adult (20-week-old) Sprague-Dawley female rats were used. Fifteen rats underwent ovariectomy (OVX group), and the other ten rats were sham-operated (Sham group). One and four weeks after surgery, muscular oxidative capacity was measured using ³¹P-MR spectra of the gastrocnemius-plantaris-soleus (GPS) muscles group at rest and during electric stimulation. Wet weight and maximum tension of the whole GPS muscles group were also measured. From the MRS measurements, the muscle oxidative capacity in the OVX group was significantly lower than that in the Sham group (p < 0.05) at both one and four weeks after surgery. The muscle's wet weight one week after surgery in the OVX group was the same as the Sham group, while four weeks after surgery it was significantly greater than that in the Sham group (p < 0.05). There were no significant differences in maximum tension among the groups. In conclusion, in adult rats the oxidative capacity decreased due to ovariectomy despite the increase in muscle weight. It is suggested that the muscular endurance capacity in female adult athletes with sports related amenorrhea may deteriorate.

KEY WORDS: Sports-related-amenorrhea, skeletal muscle, oxidative capacity, ³¹P-MRS, ovariectomy.