Effect of load and carrying position on the electromyographic activity of the gluteus medius muscle during walking.

Physical therapists often teach people with hip osteoarthritis ways to decrease gluteus medius muscle activity of the stance limb during gait. The rationale for decreasing this muscle activity is that hip muscle contraction needed for frontal plane hip stabilization is responsible for a large component of the hip joint compressive forces during stance. The magnitude and carrying position of external loads during walking are both variables that influence requirements of gluteus medius muscle force. Therefore, the purpose of this study was to determine through EMG, the relative amounts of gluteus medius muscle electrical activity produced during the stance phase of gait when subjects used varying combinations of load size (10 and 20% of body weight) and carrying position of the hands (contralateral or ipsilateral to a given hip, or anterior or posterior to the chest). We studied 24 healthy subjects and used their EMG activity during the stance phase of gait as an indication of the relative amount of myogenic hip compression force. Results indicated statistical differences in EMG according to carrying condition with the contralateral position (with loads of 10 and 20% of body weight) producing the highest levels of EMG. We discuss the kinesiologic reasons for results and the prevention of hip osteoarthritis in occupational settings.