Modulation of frontal-plane knee kinematics by hip-extensor strength and gluteus maximus recruitment during a jump-landing task in healthy women.

CONTEXT Abnormal lower extremity kinematics during dynamic activities may be influenced by impaired gluteus maximus function. OBJECTIVE To examine whether hip-extensor strength and gluteus maximus recruitment are associated with dynamic frontal-plane knee motion during a jump-landing task. DESIGN Exploratory study. SETTING Biomechanics laboratory. PARTICIPANTS 40 healthy female volunteers. MAIN OUTCOME MEASURES Isometric hip-extension strength was measured bilaterally with a handheld dynamometer. Three-dimensional hip and knee kinematics and gluteus maximus electromyography data were collected bilaterally during a jump-landing test. Data were analyzed with hierarchical linear regression and partial correlation coefficients (α = .05). RESULTS Hip motion in the transverse plane was highly correlated with knee motion in the frontal plane (partial r = .724). After controlling for hip motion, reduced magnitudes of isometric hip-extensor strength (partial r = .470) and peak gluteus maximus recruitment (partial r = .277) were correlated with increased magnitudes of knee valgus during the jump-landing task. CONCLUSION Hip-extensor strength and gluteus maximus recruitment, which represents a measure of the muscle's neuromuscular control, are both associated with frontal-plane knee motions during a dynamic weight-bearing task.