Effects of the Different Movement Forms on Bone Mineral Metabolism in Rats

The constant influence of weightlessness during space flight leads to modifications of several physiological processes. Degradation of physical performance of astronauts after long-duration space missions in one of the topical but still unresolved problems of space medicine. The phenomenon is commonly interpreted as a consequence of deconditioning of not only anti-gravity muscle but also bone structure because of long absence or reduction of mechanic and gravitational loads. It is well known that osteoporosis are affected by aging and insufficiency gravity stimulus as the human walking. The present study investigate the influence of such gravitational exercise as drop jump compare to swimming exercise in improving of bone minerals.

The study was carried out with 21 wister rats divided into three groups each 7 rats, i.e. gravitational exercise(drop jump), low gravitational exercise(swimming) and  control. The experimenters were performed after basically 5weeks breeding. During experiments period for 8 weeks all animals were given standard laboratory diet and water available freely per day. It was increased gravitational effects on drop jump from 25cm(1 week), 30cm(2 week),35cm(3 week) to 40cm(4-8 weeks) as gravitational training. In swimming group as low gravitational exercise were performed swimming 1 hour per day in 5 times per week by automatically pumping wave. The present study was carried out in accordance with the Japanese law, which allows experiments on laboratory animals in Nippon Sports Science University accordance to the Princeples of laboratory animal care. After each one week exercise, hole femoris bone was isolated, bone density diagnosis both bone mineral content (BMC,g) and bone mineral density (BMD,g/cm²). One-way ANOVA was used for statistical analysis of data between difference group, and P<0.05 was accepted for significance.

No significant changes in both BMD and BMC in response from initial week to until 5 weeks were observed. Significant change in increasing was observed in 6 and 7 weeks training both BMD and BMC(P<0.05). Overall there were not show the trend in irder of decending both BMC and BMD for jump, swimming and control, respectively from inital week to 5 weeks. We found good exercise condition as gravitational effect for intensity and periods. The above-mentioned results indicate that the jump training can increase both BMC and BMD over 6 weeks, but not under 5 weeks. The gravity load but not swimming, is more susceptible to bone minerals transit time than the exercise intensity.