The effects of different sit- and curl-up positions on activation of abdominal and hip flexor musculature.

The purpose of this study was to evaluate abdominal muscle activation with variations in trunk flexion (sit or curl up) positions, including the protocol currently used by the Canadian Society of Exercise Physiology (CSEP) Health and Fitness Program. Electromyographic (EMG) data were collected during isometric contractions from the upper rectus abdominis (URA), lower rectus abdominis (LRA), external obliques (EO), lower abdominal stabilizers (LAS), rectus femoris (RF), and the biceps femoris (BF) in 14 subjects. Sit-up positions were varied and randomized through 3 variables: the distance the hand traveled along the floor (5, 10, or 15 cm), bent knee or extended knee, and fixed or non-fixed feet. In regard to the distance the hand traveled along the floor, the 10 cm position produced the highest activation of the LRA (p = 0.02), the 5 cm distance produced the lowest RF activation (p = 0.001), and the 15 cm distance produced the lowest activation of the URA (p = 0.001). There was no significant difference between bent-knee and extended-leg sit-up positions; however, there was a trend (p = 0.1) showing that the bent-knee sit-up position produced higher levels of LAS activation and lower levels of RF activation. Foot fixation resulted in significantly lower activation levels of all abdominal sites and higher levels for the RF (p < 0.0001). The technique used for the CSEP Health and Fitness program partial curl- or sit-up test produced the highest or equal activation levels for all abdominal muscle sites.