Abstract
[Purpose] The purpose of this study is to compare the rectus abdominis and multifidus muscle activity and rectus abdominis/multifidus ratio ratios during various leg-raising exercises. [Subject and Methods] This study was conducted on 10 healthy males. Leg-raising exercises were performed in four different positions. [Results] The activity of the rectus abdominis was greatest for raising the legs while flexing the trunk. The rectus abdominis/multifidus ratio value of co-contraction of the rectus abdominis and multifidus was lowest for raising the legs while flexing the knees. [Conclusion] Raising the legs while flexing the knees, which provides the significant co-contraction of the rectus abdominis and multifidus, is recommended for treating vertebral instability in patients with back pain.