The Effect of a Vertical Load on Gluteus Medius Activity and Gait Characteristics during Walking

[Purpose] The present study examined the activity and the gait characteristics of the gluteus medius and the trunk stability muscles during the stance phase of gait on level ground when a vertical load corresponding to 0%, 1%, or 2% of body weight was placed on the lower extremities during the swing phase of the gait. [Methods] The subjects were 40 young males aged between 21 and 30 years. The vertical load, corresponding to 0%, 1%, 2% of weight, which was measured with an electronic scale, was placed bilaterally 3 cm above from the upper part of the lateral malleous. Electrodes were symmetrically attached to the gluteus medius, erector spinae, external oblique, and internal oblique muscles. [Results] There were significant differences in the activities of the left gluteus medius, bilateral external oblique, and right internal oblique muscles among the vertical loads of 0%, 1%, and 2% during gait. [Conclusion] Increases in vertical load were accompanied by changes in the activities of the internal and external oblique abdominal muscles to ensure the stability of the trunk under the different loads. Gait was only possible with the activity of the gluteus medius muscle and the trunk muscles resisting the different vertical loads rather than activating other muscles of the lower extremities in terms of energy efficiency.