Sit-up exercises: an electromyographic study.
The effect of 5 different sit-up regimens on the abdominal muscle activity were investigated by electromyography as well as the degree of lumbar flexion required with each type of sit-up. In the long-lying position the rectus abdominus muscles were only active an average of 34% of the sit-up cycle. The greatest duration of activity (90%) was found in the shoulder lift hook-lying (knees flexed) sit-up in which the subject elevates the trunk to the point where the scapula is lifted from the mat. In addition, this sit-up requires minimal flexion of the lumbar spine (3 degrees versus 38 degrees) and is less likely to result in increased forces across the lumbar disk. The evidence is that this sit-up is the most effective in terms of abdominal muscle activity and the safest in terms of causing lumbar spinal flexion.
D000009:Abdominal Muscles / Q000502:physiology*; D004576:Electromyography; D005260:Female; D006801:Humans; D005082:Physical Exertion