Effects of a progressive loading exercise program on the bone and skeletal muscle properties of female osteopenic rats.

The aim of this study was to determine the effects of a progressive loading exercise program on the bone and skeletal muscle properties of female osteopenic rats. Forty female Wistar rats (12 weeks old) were divided into four groups (n=10): sham-operated sedentary (SS); osteopenic-sedentary (OS); sham-operated training (ST) and osteopenic training (OT). Osteopenia was induced by ovariectomy (OVX). The exercise program was performed every 48 h for 8 weeks and consisted of four bouts of 10 jumps. After 8 weeks, the animals were sacrificed and submitted to bone and muscle excision. The tibias were submitted to an evaluation of the physical properties and a biomechanical test. The soleus and tibialis anterior muscles were weighed and frozen for a cross-sectional area evaluation. Osteopenic sedentary animals showed a decrease in bone strength, weight and density. The OT group showed higher values for ash weights, bone mineral density and strength, as compared to the OS group. The soleus and tibialis anterior muscles of the OT group weighed more than those of the osteopenic sedentary and ST groups. Moreover the muscle weight showed a significant positive correlation to bone strength. The results of this study suggest that the exercise program had a stimulatory effect on the bone and muscle tissue of osteopenic rats, leading to the suggestion that muscle tissue hypertrophy could have a stimulatory effect on bone mass.