The purposes of this study were to assess the activity of selected muscles used during 4 sit-up exercises with and without the assistance of abdominal exercise devices and to determine what effect, if any, the devices have on muscle activity. Nineteen young, healthy subjects completed a series of unassisted abdominal exercises (basic crunch with arms up, basic crunch with arms down, oblique crunch, and reverse crunch). The same exercises also were performed using each of 4 exercise devices. Surface electromyography was recorded from the upper and lower rectus abdominis, external oblique, rectus femoris, and sternocleidomastoid during the concentric and eccentric phases of each repetition. Repeated-measures analysis of variance analyses were used to ompare mean electromyographic activity across conditions. Results showed few significant differences in abdominal muscle activation among the conditions. Some differences were noted in rectus femoris and sternocleidomastoid activity when comparing unassisted exercise and exercise using the devices. The results suggest that abdominal devices such as those tested in this study do not elicit any greater or lesser involvement of the abdominal musculature than does performing similar exercises unassisted.
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