Sex-Specific Relationships Between Hip Strength and Hip, Pelvis, and Trunk Kinematics in Healthy Runners.

Weak hip muscle strength and excessive hip motion during running have been suggested as potential risk factors for developing patellofemoral pain syndrome (PFPS) in females, but not males. There is conflicting evidence on the relationship between hip strength and hip kinematics, which may be partly due to sex differences in the relationship between these parameters. Hip, pelvis, and trunk kinematics were collected while 60 healthy, habitual runners (23 females, 37 males) ran overground, and isometric hip abduction and external rotation strengths were measured bilaterally. Pearson correlation coefficients quantified sex-specific correlations between hip strength and kinematics, and unpaired t tests assessed sex differences in hip strength and kinematics. Hip abduction strength was moderately and inversely correlated to hip adduction excursion in females, and pelvic internal rotation excursion in males. Hip external rotation strength was moderately and inversely correlated to trunk flexion excursion in females. Finally, females displayed less hip external rotation strength and greater excursion at the hip and trunk during running compared to males. Despite the significant correlations, the relatively low r values suggest that additional factors outside of strength contribute to a substantial portion of the variance in trunk, pelvis, and hip kinematics.