Abstract
The purpose of this study was to investigate the effect of hip position on the peak torques produced during isokinetic flexion and extension of the knee. Twenty-three normal subjects participated in the study. Using the Cybex II Dual Channel Dynamometer. the peak torques of knee flexion and extension of the dominant lower limb were evaluated with the hip fixed at 5. 80. and 110 deg of flexion. Varying hip position did not significantly affect the peak torques of knee extension. However. the peak torque of knee flexion produced at 5 deg of hip flexion was dramatically (25%) less than that possible at 80 or 110 deg (torque at 80 deg > 110 deg > 5 deg). Consideration of the anatomy of the knee flexors and extensors demonstrated that the isokinetic torque curves conform to standard interpretations of length-tension relationships. It was concluded that (1) quadriceps femoris acts as a uniarticular muscle inasmuch as the peak torque of the isolated rectus femoris is minimally affected by hip position; (2) the peak torque of the biarticular hamstrings varies significantly with hip position; (3) the contribution of body weight should be considered when comparing peak muscle torques; and (4) length-tension relations must be considered in selecting test. exercise, and rehabilitative parameters for the knee.