Hip Strength and 3-D Mechanics During Running and Squatting in Asymptomatic Female Runners

Abstract

Diminished hip strength in females with patellofemoral pain syndrome (PFPS) has been linked to excessive hip internal rotation (HIR), hip adduction (HADD) and contralateral pelvic drop (CPD). These relationships have also been found in healthy females, but only in the frontal plane. There have been no studies of correlations between hip strength with 3D kinematics in healthy females. This information may be helpful in identifying individuals who may be at risk for PFPS.FIGUREPURPOSE: To establish a relationship between hip strength and 3-D mechanics in asymptomatic individuals. It was hypothesized that hip abductor strength (HABDS) would correlate with HADD and CPD, and hip external rotator strength (HERS) would correlate with HIR during both running and a single leg squat (SLS). METHODS: 40 healthy female runners (22.7 yrs, 15.2 miles/wk) were recruited. Peak isometric HABDS and HERS were collected via a hand-held dynamometer. Kinematic data were then collected at 200 Hz while subjects performed 5 SLS's to 45° knee flexion, and while they ran on a treadmill at 3.35 m/s. Peak HADD, HIR, CPD were calculated. RESULTS: Unexpectedly, HABDS was not significantly correlated with either HADD or CPD during running or during the SLS. In addition, HERS was not significantly correlated with HIR during either activity. CONCLUSIONS: The lack of correlation between hip strength and hip kinematics may be due to the fact that this study examined healthy individuals in a fresh state. These correlations may be stronger once a threshold of weakness is met, which may be present in a more fatigued state. Additionally, timing of hip muscle firing may be more strongly correlated with hip kinematics than isometric strength. Support: NIH 1 S10 RR022396, DOD W911NF-05-1-0097