EFFECT OF INTENSIVE TRAINING ON LOWER LEG STRUCTURAL STRENGTH - AN IN-VIVO STUDY IN OVARIECTOMIZED RATS

The aim of this study was to investigate the effect of training on the in vivo tibial structural strength during the development of post-ova riectomy osteoporosis. Seventeen mature Wistar rats (215 g) were ovari ectomized and randomized into two groups. The sedentary control group was kept cage confined, while 3 days postoperatively the trained group started treadmill running with high intensity for 1 h 5 days a week. All were given a low calcium diet (Ca 0.01%). After 8 weeks the animal s were anaesthetized and the right lower legs fractured during muscle contraction in three-point ventral bending. The left legs were fractur ed al the same level after removal of all soft tissues. Histomorphomet ry of the meta- and diaphysis of the distal tibiae was performed. Weig ht-gain was higher in sedentary (108 g) than in trained (61 g) rats (P <0.0001). There were no significant differences in mechanical results between the groups at in vivo or in vitro fracture. Correcting for wei ght-gain differences did not change these results. Histomorphometry sh owed no differences between the groups. Corticosterone was higher in t rained than in sedentary rats (P<0.02), and corticosterone may have ha d a negative influence both on muscle and bone. The study could not sh ow an effect of high intensity training in the early phase after ovari ectomy on in vivo or in vitro fracture strength.