Faculty Publications


Quadriceps muscle group activity related to hip angle and load

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Clinical Kinesiology





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Rehabilitation of the knee requires attention to each of the three superficial quadriceps muscles the rectus femoris (RF), the vastus medialis (VM), and the vastus lateralis (VL). The bi-articular nature of the RF dictates that the angle of the hip joint will have an effect on the nature of the activity in this muscle. The nature of this effect was the focus of this study. Twenty-four female subjects were tested under three load and three hip angle conditions. The EMG activity in each of the three muscles (RF, VM and VL) was recorded during both concentric and eccentric contraction states. Weights attached to the foot provided resistance of either no load, 50% or 70% of the maximum lift weight. Across load conditions activity in the VM and VL muscles doing both concentric and eccentric contractions increased significantly (p < .001) at a 90° angle of hip flexion. There was no significant change in RF activity across hip flexion angles. It was concluded that a hip flexion angle of 90° provides for the greatest combined level of activity in all three of the superficial quadriceps muscles during knee extension, while hip flexion angles of 45° and 0° produce greatly reduced levels of activity in the VM and VL muscles.

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