The effect of leg length asymmetry on leg stiffness and dynamic postural stability in vertical landing

Abstract

Background: Assessment of asymmetries in dynamic postural stability and lower extremities kinetics during landing technique are considered factors for injury prevention and achieve optimal athletic performance. Nevertheless, the relationship between these factors has not been established. This study aimed to investigate the effects of leg length asymmetry on dynamic stability and leg stiffness upon initial contact with the ground after vertical landing. Methods: Twenty healthy adult men landed on the ground from a height of 30 cm; we measured leg length, leg stiffness, lateral pelvic tilt angle, peak vertical force (PVF), the loading rate, dynamic postural stability index (DPSI), and the correlations among these variables. Results: At initial contact, the right leg was significantly longer and showed greater lateral pelvic tilt than the left leg. These characteristics increased the loading rate at the time of PVF on the right leg, which in turn affected leg stiffness and pelvic tilt. The DPSI was also decreased for the right leg compared with the left leg. In the correlation analysis, we observed strong, positive correlations and high explanatory power for PVF, the loading rate, vertical stability index, and DPSI, with r ≥0.822 and R2 ≥57%. Conclusions: The identified associations support the validity of the result, showing that the right leg failed in its rapid stabilization strategy. The leg length asymmetry is suspected to affect asymmetrical impact patterns, DPSI, and leg stiffness. Given the number of individuals with leg-length inequalities who play sports relying on jumping and landing patterns, reducing the rate of injury possibly incurred.

Keywords

• vertical landing
• leg stiffness
• dynamic postural stability
• asymmetry