Activation of abdominal muscles during some physiotherapeutic exercises.

The aim was to evaluate the theoretical efficiency of some abdominal muscle exercises for strength training. Sit-up with rounded back (curl-up) from the supine position up to 45 degrees activates the straight and oblique abdominal muscles to 50% of the values for maximum isometric contraction measured as integrated EMG. This exercise was compared with two previously suggested exercises: curl-up with simultaneous activation of the plantar-flexors of the ankle activated the abdominal muscles to the same level and curl-up from a position with dorsally extended spine did not activate the muscles more. Curl-up with lateral rotation of the trunk gave a high activation of the oblique muscles. This exercise was compared with two completely isometric exercises suggested for patients with back pain: only somewhat lower activation was obtained during an exercise in supine position with lateral resistance to the knees, but with lateral resistance against the elevated forearms there was only little activation.