Purpose: The purpose of this experimental study have been testifying about reactive muscle control regarding sternocleidomastoid and psoas. Low back pain patient do not sit-up exercise without abnormality of trunk flexor. The reason of problem is unbalance sternocleidomastoid and psoas. According to George J, Goodheart who have been developing Applied Kinesiology (A. K.) since reactive muscle recognized gait testing in 1964. Materials and Methods: From September, 2004 to February, 2005, I have controled sternocleidomastoid and psoas. It is applied to the patients who are unable sit up exercise at Yang-Dong local clinic, Yang-Pyung county, Kyung-Gi Do province in Korea. 24 Patients divided 2 groups. A group is applied general physical therapy. Also B group is added reactive muscle control from M.E.M.P.T.(Korean society of muscle and energy monitoring physical therapy) Results : The results of this study follow. 1. Possible sit up group 8 persons of the second group. 2. Not possible sit up group the others. Conclusion: The study present that reactive muscle control sternocliedomastoid and psoas is useful in patient with low back pain is difficult to sit up.