A Comparison Of The Lower Extremity Kinematics Between One- And Two-leg Landings

Abstract

When landing, eccentrically controlled hip flexion, knee flexion and ankle dorsiflexion contribute to energy absorption. A recent comparison (1) of ground reaction forces between landings onto one and two-legs suggest a lander alters technique to reduce the magnitude of forces imposed in different landing situations. Comparing the kinematics at the ankle, knee and hip joints is a preliminary step in understanding technique alterations utilized for different landing situations. PURPOSE To compare lower extremity joint kinematics between drop landings onto one and two-legs. METHODS Eighteen college age females, free of lower extremity trauma, volunteered as participants. In one session, ten successful trials of one- and two-leg landings from a 38 cm stool were performed in random order by each participant; instructions were to “land comfortably”. Position of the right hip, knee and ankle joints was calculated from a sagittal plane video recording (120 Hz) beginning before contact through to maximum joint position. Five kinematic variables (touch down angle, maximum angle range of motion, peak angular velocity, and time to peak angular velocity) were calculated for each joint for each trials. The subjects' 10-trial mean values for each kinematic variable was entered into a paired t-test (α=.05) to identify statistical differences. RESULTS At contact, participants exhibited a significantly more extended position at the knee and ankle joints during one-leg landings, but not at the hip joint. During a one-leg landing, significantly less range of motion (ROM) was utilized at the hip and knee joints but significantly greater ROM was utilized at the ankle joint; thus, a more extended position was present at the hip and knee at maximum joint flexion in a one-leg landing. Between contact and maximum joint flexion, significantly lower peak angular velocities were measured at all three lower extremity joints. There were no significant differences in times to minimal joint angle or time to peak joint angular velocity. The more extended positions measured during a one-leg landing may reflect balance considerations, while the lower angular velocity values suggest reduced energy absorption. CONCLUSIONS One leg landings are characterized by more extended joint positions and lower joint angular velocities. ACKNOWLEDGEMENT Jump Rope for Heart grant from the Illinois Association for Health, Physical Education, Recreation and Dance.