Effect of long-term vibration stimulus on skeletal muscle mass and body composition in rats

Background and objectives: Many studies are being conducted on the effects of nutrient intake on exercise effects such as the promotion of muscle hypertrophy, but it is not easy to make experimental animals exercise. The main method of exercise model applied to animals is forced muscle contraction by treadmill running or electrical stimulation. However, these methods have problems in that they put excessive stress on rats and cost a lot of equipment. Therefore, it is necessary to create a model that is more affordable and has a high exercise effect. In human studies, whole-body vibration stimulus by a vibration machine has been confirmed to have effects such as improvement of muscle strength and prevention of bone density decrease. However, the effects of long-term exposure to vibrational stimulus on skeletal muscle mass, body composition, and blood components have not been fully verified, and there are few studies using rats. In this study, we examined the effect of long-term vibration stimulus on rats for 12 weeks and whether vibration stimulus was appropriate as an animal exercise model. Methods: Twenty male Wistar rats (3 weeks old) were randomized into two groups of ten rats, the control group (C) and vibration group (V), and fed with a commercial diet ad libitum for 12 weeks. Only the V group performed an exercise program using a vibration machine every day. The vibration stimulus was gradually increased from 5 min at 9 Hz to 30 min to 15 Hz. After the experimental period, all rats were sacrificed by beheading. The hind skeletal muscle, heart, liver, and abdominal adipose tissues were quickly removed and stored at −80°C until analysis. The carcass samples were stored at −20°C until analysis. Results: The relative weights of the heart, soleus muscle, and flexor halluces longus muscle were significantly higher in the V group than in the C group. However, the weight of abdominal adipose tissues and carcass fat did not differ between the two groups. Conclusion: These results suggest that long-term vibration stimulus may be an effective exercise program with aerobic and resistance exercise effects in rats.