Os efeitos de um programa de atividade física de carga progressiva nas propriedades físicas e na força óssea de ratas osteopênicas

SUMMARY Background: Many studies have shown that physical exercises are able to stimulate bone formation and increase bone mass, constituting a therapeutic modality for the treatment of bone loss due to osteoporosis. However, some points about the intensity, duration and frequency of the exercises remain confusing and contradictory. Thus, the aim of this study was to determine the effects of a progressive loading exercise program on femur of osteopenic rats. To induce osteopenia, we used the animal model of ovariectomy (OVX). Forty animals were studied and divided into 4 groups: sham-operated sedentary (SS); ovariectomy-sedentary (OS); sham-operated training (ST) and ovariectomy training (OT). The trained groups performed jumps into water: 4 series of 10 jumps each, with an overload of 50% to 80% of the animal's body weight, during 8 weeks. Femora were submitted to an evaluation of physical properties, a biomechanical test, calcium and phosphorus content measurement and a morphometric histological evaluation. Results: osteopenic animals showed a decrease of bone strength and lower values of bone weights, bone density and calcium con- tent. The exercised osteopenic rats showed higher values of geo- metrical, physical properties, bone strength and calcium content compared to controls. The results of the present study indicate that the progressive loading exercise program has stimulatory effects on osteopenic rats' femora. It seems that the intensity and duration of the used protocol produced bone structural adaptations, which contributed to revert bone loss due to ovariectomy.