Gender Differences in Lower Limb Biomechanics During Stair Ascent in Young Subjects

The aim of this study was to investigate gender differences in the biomechanics of lower limb joints during stair ascent, focusing on the distribution of joint loads. Thirty-six young subjects (18 males and 18 females) ascended instrumented stairs while kinematic and kinetic data were measured. Mechanical variables of the lower limb joints and body posture on the sagittal plane were compared between genders, and their associations were also investigated. Female subjects exerted more mechanical work, power, and joint moment than male subjects at the knee joint, while males exerted more at the hip joint. Females and males showed a longer moment arm of ground reaction force at the knee and hip joints, respectively. The moment arm, but not the magnitude, of ground reaction force was strongly associated with the joint moment (r = 0.80–0.97). Females exhibited a more crouched stance limb (lower heel lift, greater ankle dorsiflexion, and knee flexion) than males. A more crouched and extended lower limb posture was found to be correlated with a longer moment arm at the knee and hip joints, respectively. Half of the variance in moment arm could be explained by the heel lift angle. The results indicate that females allocate greater work to the knee joint but less to the hip joint than males do in order to elevate body mass to a higher step during stair ascent. The work distribution strategy appears to be influenced significantly by posture, particularly the choice of foot contact method: heel-toe standing in females and toe standing in males.