The purpose of this study was to estimate the effect of horse riding exercise. Twenty female subjects exercised horse riding using SRIDER. Subjects exercised 30 min a day each mode, three days per week for 4 weeks in a constant temperature and humidity environment. We measured lumbar joint torque using the BIODEX System3 to estimating improvements in muscle strength and reaction. The results of muscle strengthening and muscular reaction showed that peak lumbar joint torque in whole body mode and abdomen mode were higher than the other modes. This mode of horseback riding movement would be stimulated sensory and motor nerves mostly, which improved muscle reaction. Also continuous movement of those modes of horseback riding can reduce muscle tonus and relax stiff muscles. We found that whole body exercise and abdomen exercise could be most improved muscle strength efficiently for muscle strength, and muscular reaction.