The Influence of Hip Flexion and Isokinetic Velocity on Hamstrings-Quadriceps Strength Ratios in Healthy Females.

ABSTRACT

Context Measurements of the concentric hamstrings-quadriceps strength ratio (HcQc) are almost exclusively recorded in the upright, seated position (hip flexion 80-100°) on an isokinetic dynamometer at angular velocities ranging from 30°/s to 360°/s. Further, there is a scarcity of data examining HcQc ratio in females. Objective: To compare the effects of hip-flexion position (0°, 45°, and 90°) and isokinetic velocity (60°/s, 180°/s, and 300°/s) on knee-extension and knee-flexion torques and the HcQc ratio of females. Design: Single-session, repeated measures. Setting: Biomechanics laboratory. Participants: Twenty-seven healthy young female adults. Intervention Participants completed five repetitions of isokinetic, concentric knee-flexion and knee-extension at hip flexions of 0° (supine), 45° (midrange), and 90° (traditional), at 60°/s, 180°/s, and 300°/s. Main Outcome Measures: Knee extension and flexion average peak torque (PT) and resultant HcQc ratios. Results: Knee-extension average PT was significantly influenced by isokinetic velocity but hip-flexion position was not. Compared to 90°, knee-flexion average PT was significantly greater in the 45° and 0° hip positions, coupled with greater average PT decreases between 60°/s and 180°/s than between 180°/s and 300°/s. HcQc ratios in the 0° position were significantly greater than in the other positions and increased significantly as testing velocity increased. Conclusions: Exclusively using a seated, upright position during knee isokinetic testing on females may misrepresent knee strength at more-functional hip positions. We recommend evaluating isokinetic knee strength using a supine position to better reflect hip positions during daily and sporting activities, throughout movement specific velocities.