Effect of hip position and breathing pattern on abdominal muscle activation during curl-up variations

Recent studies have indicated that applying different breathing pattern and changes of extremity positions could be a useful way of performing challenging exercises that include coactivation of the abdominal muscles. The aim of this study was to investigate the effects of changes of breathing pattern and hip position on abdominal muscle activity during curl-up exercises. Surface electromyography responses of the rectus abdominis (RA), internal oblique (IO), external oblique (EO) muscles and rectus femoris (RF), and Borg rating of perceived exertion (Borg RPE) score were investigated during the curl up exercises. A total of 20 healthy, physically active male volunteers completed two hip positions (45° and 90° hip flexion) and three breath types (slow expiration, maximal inspiration, and maximal expiration) for curl-up variations. The curl-up with 90° of hip flexion significantly increased the muscular activities of IO, EO, RF, and Borg RPE score (P<0.05). The curl-up with maximal expiration significantly elevated the IO and EO activity, compared to other breathing conditions. There were no significant difference in RA activities (P>0.05). The present study showed both the hip position and breathing pattern affect abdominal muscle activities during the curl-up exercise, especially of the oblique muscles. Among the breathing patterns investigated herein, the curl-up with maximum expiration produced greater activation of the oblique muscles compared to slow expiration and maximum inspiration.