The purpose of this study was to investigate the effects of horizontal alignment of lower limb segment during hip abduction in side-lying (ABD) and clamshell (CL) exercise.
The subjects of the study were twenty healthy men without low back pain or lower limb pain. Subjects performed four gluteus medius exercises : hip abduction in side-lying (ABD), hip abduction in side-lying with horizontal alignment of lower limb segment (ABD-H), clamshell (CL), clamshell with horizontal alignment of lower limb segment (CL-H).
Surface EMG was used to measure hip abductor muscle activity and recruitment pattern from the five muscles : gluteus medius (Gmed), tensor fascia latae (TFL), gluteus maximus upper fiber (GmaxU), gluteus maximus lower fiber (GmaxL), and quadratus lumborum (QL).
A two-way repeated measures analysis of variance was used to determine the statistical significance of the Gmed, TFL, GmaxU, GmaxL, QL.
TFL EMG activity was significantly greater in ABD than in ABD-H. Gmed EMG activity was significantly greater in CL than in CL-H. Gmed, TFL, QL EMG activities were significantly greater in ABD type of exercises than in CL type of exercises. GmaxU, GmaxL EMG activities were significantly greater in CL type of exercises than in ABD type of exercises.
In terms of the order in muscle recruitment, there was a difference between ABD type of exercises and CL type of exercises. However, there was no significant difference in each type of exercises in horizontal alignment of lower limb segment factor.
The results of this study suggest that the CL type of exercises can lower the activities of the TFL and QL, more than ABD type of exercises. Moreover, in respect of the muscle recruitment order, the CL type of exercises have more advantages than ABD type of exercises. In addition, in CL type of exercises, the CL exercise was found to be effective in strengthening the Gmed rather than the CL-H exercise. However for the sole purpose in strengthening Gmed, ABD type of exercises are more suitable than CL type of exercises. In addition, in ABD type of exercises, ABD-H can lower the activity of the TFL than ABD.