2004 Volume 31 Issue 1 Pages 9-14
The aim of the present study was to investigate the differences in activity among the three parts of the gluteus medius (GMed), tensor fasciae latae (TFL) and the superior part of the gluteus maximus (Gmax) muscles. Seven healthy volunteers participated in this study. The individual EMG activities of the hip abductor muscles, i.e., the anterior part of the GMed, the middle part of the GMed, the posterior part of the GMed, TFL and the superior part of the Gmax muscles, were detected using a bipolar fine wire electrode. And the integrated EMG (IEMG) of each muscle-hip position relationship, the maximum hip abduction torque-hip position relationship and the isometric hip abduction torque-IEMG relationship were analyzed.
As results, during the maximum isometric hip abduction, the IEMG of the anterior part of the GMed muscle and maximum hip abduction torqe decreased significantly as the hip flexion angle increased (p < 0.01). The EMG activities of the hip abduction muscles varied with the change in hip rotation angle except for the superior part of the Gmax muscle under the maximum isometric hip abduction. And the IEMG of the three parts of the GMed and TFL detected at a hip position of external rotation were significantly lower than those at a hip position of neutral and internal rotation. In addition, the maximum hip abduction torque was the largest at a hip neutral position.
The relationship between the isometric hip abduction torque and the IEMG of the three parts of GMed muscle showed a linear relation, and the IEMG of these parts of GMed and TFL muscles increased as the hip abduction torque increased from 0 to 80% maximum voluntary contraction. However, the IEMG of the superior part of the Gmax muscle did not vary as the hip abduction torque increased.
These results were considered to demonstrate a part of functional difference among the three parts of the GMed, TFL and the superior part of the Gmax muscles.
