Endurance training and bone metabolism in middle-aged rats

This study was performed to observe the influence of moderate treadmill run ning on bone of middle-aged male rats. Seventy 15-month-old Wistar rats wer e used. Ten initial controls (IC) were killed on day 0. Among the 60 others , three groups of ten exercised rats (E) run 1 h/day, 6 days/week at 60% of their maximum aerobic capacity. On days 30, 60 and 90 of the training peri od, 20 rats, ten E and ten R (resting animals), were killed. Femoral failur e stress never varied and was never different in E and R during the experim ent. On day 90 whole body mineral content and mineral density were higher i n E than R. Simultaneously, total, diaphyseal and metaphyseal femoral densi ties were lower in R than IC or than in E. No difference was observed betwe en IC and E. In resting rats, urinary deoxypyridinoline excretion (a marker of bone resorption) increased between days 0 and 90, while it did not chan ge in runners. These results indicate that in middle-aged rats, moderate ru nning prevents decrease in bone mineral density, probably by inhibiting bon e resorption. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.