Male and female gluteal muscle activity and lower extremity kinematics during running.

BACKGROUND: Patellofemoral pain is one of the most common lower extremity overuse injuries in runners and is significantly more common in females. This study evaluated differences in the timing and magnitude of gluteal muscle activity as well as hip and knee joint frontal and transverse plane kinematics between male and female runners in the context of this gender bias.
METHODS: Twenty healthy male and 20 healthy female runners were participants. Three-dimensional lower extremity kinematics, and gluteus medius and gluteus maximus muscle activation were recorded using motion analysis and electromyography as subjects ran at 3.7 m/s (+/-5%). Comparisons of hip and knee joint kinematic and gluteus muscle activation data were made using independent t-tests (α=0.05).
FINDINGS: Females ran with 40% greater peak gluteus maximus activation level (P=0.028, effect size=0.79) and 53% greater average activation level (P=0.013, effect size=0.93) than males. Female runners also displayed greater hip adduction (P=.001, effect size=1.20) and knee abduction (P=0.011, effect size=0.87) angles at initial contact, greater hip adduction at peak vertical ground reaction force (P<0.001, effect size=1.31), and less knee internal rotation excursion than males (P=0.035, effect size=0.71).
INTERPRETATION: Greater gluteus maximus activation levels during running may predispose females to earlier gluteus maximus fatigue, promoting altered lower extremity running kinematics thought to be associated with the etiology of patellofemoral pain. Gender differences in transverse and frontal plane hip and knee kinematics observed in this study may also contribute to the gender bias for patellofemoral pain among females.