The Effects of Curl-Up and Straight Leg Raising Exercises in Different Hip Joint Positions on Abdominal Muscle Thickness

Objective: The purpose of this study was to investigate the effect of combining 2 exercises at different angles of the hip joint on the thickness of the transverse abdominis and internal oblique muscles. Methods: Twenty-eight healthy adults (22.7 ± 2.5 years of age; 64.93 ±8.8 kg; body mass index: 22.2 ± 2 kg/m²) performed the curl-up exercise and straight leg raise with external rotation of the hip and dorsiflexion of the ankle simultaneously. The thicknesses of transverse abdominis and internal oblique muscles were measured from right and left sides while resting, in curl up, curl up with 10º flexion of hip, curl up with 15º flexion of hip, and curl up with 10º flexion and 15º abduction of the hip. The means of muscle thicknesses were compared using repeated-measures analysis of variance and post hoc Bonferroni tests in the 5 positions. Results: The thicknesses of transverse abdominis (P < .001) and internal oblique (P < .001) muscles were significantly greater in curl up with 10º flexion and 15º abduction of hip compared with the other positions. There was no significant difference between abdominal muscle thicknesses in measuring from either side. Conclusion: Doing the curl-up exercise with 10º flexion and 15º abduction of the hip may be beneficial in strengthening deep abdominal muscles.