Hip Strength Correlates More With Frontal Plane Than Sagittal Plane Knee and Hip Kinematics During a Stop-jump

Abstract

Associations of hip strength and jump-landing kinematics have been proposed as modifiable risk factors for lower extremity injury. PURPOSE: The purpose of this study was to evaluate the association of isometric hip strength on knee and hip kinematics during a running stop-jump task (RS). METHODS: Lower extremity biomechanics of 15 female collegiate soccer athletes (19±.7 years, 1.67±.1 m, 61.7±8Kg) were obtained. Subjects performed five trials of an unanticipated RS task. Hip isometric strength (flexion (FLX), extension (EXT), abduction (ABD), and adduction (ADD)) were evaluated for the dominant leg utilizing a portable fixed dynamometer system (BTE Evaluator) in a standing position with data reported as normalized mean torque to height x weight. Kinematic variables measured at initial contact (IC) and peak vertical ground reaction force (PVGRF) consisted of abduction and flexion angles for the right knee and hip, respectively. Separate Pearson's product-moment correlation coefficients were conducted with an alpha level set at.05. RESULTS: Hip flexion angle at IC increased with a weak association (R2=.30) with increased hip ADD strength. Knee flexion angle at PVGRF increased with a weak association (R2=.28) with increased hip ADD strength. Knee abduction angle at IC increased with a weak to moderate association (R2=.28 to.49) with increased strength in all four directions at PVGRF increased with a moderate association (R2=.59) with increased hip FLX strength. Hip ABD angle at IC decreased with a moderate association (R2=.35 to.39) with increased hip FLX, EXT, and ADD strength at PVGRF decreased with a moderate association (R2=.44 to.50) with increased hip FLX, EXT, and ADD strength. CONCLUSION: Isometric hip strength measures had significant weak to moderate association with frontal plane knee and hip kinematics, yet were minimally associated with sagittal plane motions. Hip ABD strength values were moderately associated with knee abduction angles. Future evaluation of hip strength and its association to jump-landing kinematics needs to be conducted in a prospective study designed to evaluate those at increased risk for lower extremity injury to develop targeted prevention plans. National Institutes of Health RO3: PA 04-002 NIAMS Small Grant Program for New Investigators: 1R03AR054031-01