Effects of Gender on Landing Mechanics in an Unanticipated Landing Task in Children

Abstract

PURPOSE: To investigate lower-extremity biomechanical differences between preadolescent boys and girls when performing a drop-landing. The landing task incorporated a visual cue provided just prior to ground contact directing the subjects to run in one of three possible directions after landing. METHODS: Forty-four subjects (20 males & 24 females) were recruited from a local youth soccer league to participate in this study. In this preliminary analysis, data from five females (mean age = 10.8 yrs, mean mass = 37.19 kg, mean ht. = 1.45 m) and five males (mean age = 11.4yrs, mean mass = 33.82 kg, mean ht. = 1.43 m) were examined. Three dimensional lower limb kinematics were recorded at 250 Hz using a commercial motion capture system. Subjects hung with both hands from a horizontal bar (mean drop distance = 30.5 cm) and on a verbal command released their grip and dropped onto one leg landing on one of two floor mounted force plates (landing leg determined before trial commenced). Upon landing, subjects were instructed to run as fast as possible to one of three floor mounted targets placed 3.66 m in front of the landing area. Run direction was unanticipated (UA) since subjects did not know until after bar release which one of the three targets would illuminate. The targets were located directly ahead of the landing area, 30° to the left, and 30° to the right. Three trials were collected for each direction for each landing leg, resulting in straight ahead, sidestepping, and crossover trials with the order of trials randomized for each leg (18 trials/subject). In this preliminary analysis, data from left leg landings with a sidestep to the right were analyzed for coronal, sagittal, and transverse plane kinematics at the hip, knee and ankle at the time of initial contact (IC) with the ground. Differences between boys and girls were assessed for each variable using a Student's t-Test. RESULTS: Our preliminary analysis found no significant kinematic differences at the hip and ankle between boys and girls at IC. However, a significant difference between boys and girls was found for knee flexion angle at IC (p <0.04) with girls landing with less flexion than boys. No difference was found on knee valgus or rotation, and no other significant kinematic differences were found. CONCLUSIONS: Our results conflict with recent research that found differences in knee valgus but not in knee flexion at IC in middle and high school aged athletes who performed an unanticipated cutting maneuver. These preliminary results indicate that differences in landing mechanics between genders may exist prior to pubescence.