Electrically evoked knee flexion torque increases with increased pelvifemoral angles

This study was designed to determine the extent to which knee flexion torques would differ when submaximal hamstring muscle contractions were evoked by constant levels of electrical stimulation and when the pelvifemoral angle was increased. Nineteen healthy subjects (ten women and nine men) underwent electrical stimulation of the hamstring muscles while randomly positioned either supine, sitting upright, or sitting leaning forward. The pelvifemoral angle for each position was measured from lateral photographs: the knee flexion torque was calculated from the knee flexion force, and lever arms measured directly at a constant knee angle. A repeated measures ANOVA demonstrated significant differences for pelvifemoral angles (F = 485·00, P < 0·001) and knee flexion torques (F = 21·97, P < 0·001) among the positions. The mean torques in the upright and leaning forward positions were 2·2 and 3·7 times greater, respectively, than mean torques in the supine position. The increase between the supine and leaning forward positions exceeded the increase previously reported in the literature for subjects performing maximal voluntary knee flexion efforts.