Effects of two non-endurance exercise protocols on established bone loss in ovariectomized adult rats

Summary The effects of non-endurance exercise on bone properties were evaluated in 9-month-old sham-operated (SH) and ovariectomized (OVX) rats. The studies were started 3 months postsurgery, after bone mass was decreased in OVX rats. The sham and OVX rats were either kept sedentary (SED) or were trained to run with one of two protocols: 12 m/minute, 50 minutes/day, 4 days/week (low intensity, frequent, EX-1); or 21 m/minute, 40 minutes/day, 1 day/week (moderate intensity, infrequent, EX-2). A group of seven rats evaluated at the beginning of the study served as baseline control. The bone mineral was assessed by the ash weight of the left femur, tibia, and 4th lumbar vertebra. Biomechanical (strength, deformation, stress, strain, and stiffness) and morphometric (length, cortical and medullary area, moment of inertia) properties were evaluated for the right femur. There was a significantly lower bone mineral and mechanical properties in OVX-SED (n=7) than in SH-SED (n=10) rats. The OVX-EX-1 (n=6) rats had higher ash content of femur and tibia than OVX-SED rats, but the change was significant only for tibia. The EX-2 had no effect on the ash content, but femur stress was higher in OVX-EX-2 (n=8) than in OVX-SED rats. The femur yield force and deformation were improved in OVX rats with both exercise protocols, whereas the vertebra ash weight, femur strain, modulus of elasticity, length, cortical area, and moment of inertia were not changed. Non-endurance exercise did not affect bone properties in either SH-EX-1 (n=7) or SH-EX-2 (n=8) groups. We conclude that non-endurance exercise has beneficial effects on established osteopenia in ovariectomized rats.