Electromyographic activity of back musculature during Williams' flexion exercises.

The purpose of this investigation was to determine the pattern and magnitude of electromyographic activity recorded from paraspinal musculature at four different vertebral levels while subjects performed six Williams' flexion exercises with anterior and posterior pelvic tilt. Bipolar surface electrodes were placed on the right sides, at C5, T6, L3, and S1, of eight men and eight women. Integrated electromyographic activity was analyzed at the end of range of each exercise. A significant (P less than .05) interaction effect was found between exercises and types of tilt at each vertebral level. The difference in electromyographic activity between the two pelvic positions was most evident in the lumbar and sacral areas, where electromyographic activity recorded for anterior tilt was greater than for posterior tilt. The results support the following conclusions: 1) pelvic tilt, curl up, knees to chest, and hamstring stretch performed with posterior tilt minimize the electromyographic activity in the lumbar and sacral regions that occurs in conjunction with lengthening of these muscles during posterior pelvic tilt, 2) use of the standing exercises and anterior tilt positions should be avoided if minimizing electromyographic activity in the lumbar and sacral regions is desired, and 3) the electromyographic activity of each of the four different vertebral levels responded independently of every other level during performance of Williams' flexion exercises.