Effects of abdominal hollowing and abdominal bracing during side-lying hip abduction on the lateral rotation and muscle activity of the pelvis

It is important that compensatory lateral movement of the pelvis does not occur during side-lying hip abduction (SHA). The purpose of the present study is to investigate the effects of abdominal hollowing and abdominal bracing during SHA on pelvic lateral rotation (PLR) and the electromyography activity of the gluteus medius, quadratus lumborum (QL), external oblique abdominis (EO) and internal oblique abdominis (IO). A total of 22 healthy male adults participated in the study. The subjects performed three conditions in side-lying in random order: SHA with abdominal hollowing (SHA-AH), SHA with abdominal bracing (SHA-AB), and SHA without any condition (SHA-WC). The angle of PLR in SHA-AB was significantly lower compared to SHA-AH and SHA-WC, and angle of PLR in SHA-AH was significantly lower than that in SHA-WC. The muscle activity of the QL was significantly greater for SHA-AB compared to SHA-AH and SHA-WC. The muscle activity of the EO was significantly greater for SHA-AB compared to SHA-AH and SHA-WC. And the muscle activity of the EO for SHA-AH was significantly greater than that for SHA-WC. The muscle activity of the IO was significantly greater for SHA-AH and SHA-AB compared to SHA-WC. Based on these results, we suggest that abdominal bracing increases the muscle activity of QL, EO, and IO, and decreases the angle of PLR compare to abdominal hollowing during SHA.