The influence of lateral body weight shift during single-leg raising in a sitting position while stepping into a bathtub on integrated electromyograms of the external abdominal oblique muscle alone, overlapping abdominal oblique muscles, and internal abdominal oblique muscle alone on the weight-bearing and nonweight-bearing sides were investigated in 14 healthy subjects. Each subject was seated on 2 body weight scales arranged under the buttocks and asked to raise one leg and shift their body weight onto the contralateral gluteal region. Electromyography revealed a significant increase in the electromyograms of the external abdominal oblique muscle alone, the overlapping abdominal oblique muscles, and the internal abdominal oblique muscle alone on the ipsilateral side of the raised leg (p<0.05). The muscle activity the internal abdominal oblique muscle alone on the weight-bearing side increased as the weight load increased to 80%, and then decreased to the initial level as the weight load increased to 90%-95%. These findings suggest that, to practice lateral body weight shift during single-leg raising in a sitting position during the early motion of stepping over something from a sitting position, the external abdominal oblique muscle alone, the overlapping abdominal oblique muscles, and the internal abdominal oblique muscle alone on the weight-bearing and non-weight-bearing sides should be individually evaluated because the actions of each muscle region are different.
