An electromyographic comparison of abdominal muscle synergies during curl and double straight leg lowering exercises with control of the pelvic position.

STUDY
DESIGN: This prospective study evaluated the abdominal muscle activity during the Isometric bent knee curl and double straight leg lowering exercise.
OBJECTIVES: To compare the magnitude of the electromyographic activity across the curl and double straight leg lowering exercise and determine if the muscle synergies were specific to a given exercise. SUMMARY OF BACKGROUND DATA: Abdominal muscle strengthening exercises are frequently recommended in the prevention and rehabilitation of individuals with low back pain. Previous studies comparing the curl exercise with the double straight leg lowering exercise did not support the notion that the double straight leg lowering exercise is more demanding on the abdominal muscles. No previous study examined these two exercises while maintaining a constant pelvic position.
METHODS: Fifteen male subjects had the electromyographic activity of the rectus abdominis, the external oblique, and the internal oblique abdominal muscles evaluated during the curl and double straight leg lowering exercise. The same position of the posterior pelvic tilt was maintained between each exercise using feedback from an electrogoniometer attached to the pelvis.
RESULTS: The double straight leg lowering exercise resulted in significantly greater activation of the abdominal muscles compared with the curl. Two abdominal muscle synergies emerged during the double straight leg lowering exercise: synergy I exhibited high rectus abdominis, high external oblique, and low internal oblique muscle activity, whereas synergy II exhibited low rectus abdominis, high external oblique, and high internal oblique.
CONCLUSIONS: The results support the use of the double straight leg lowering with the posterior pelvic tilt for achieving greater abdominal muscle coactivation in an exercise program.