Sagittal and frontal lower limb joint moments during stair ascent and descent in young and older adults.

Stair negotiation is an essential skill required for independent mobility, and is described by older adults as a challenging task that is associated with high fall risk. Little is known about the age-related changes in joint kinetics and the relative contribution of lower limb joint moments during stair negotiation. This study characterized lower extremity joint kinetics and their variability associated with stair ascent and descent in young and older adults. Twenty three young and 32 older adults (>55 years) participated. Three dimensional, bilateral gait analysis provided ankle, knee, and hip moment profiles, which in the sagittal plane were summed to provide the support moment. In addition, intra- and inter-subject coefficients of variation were calculated for ensemble averaged curves. Age-related differences were found in the magnitudes of the moment contributions during event transitions for stair ascent and descent. Within groups, the moment profiles were generally consistent. Ankle and knee moments predominantly contributed to extensor support in the sagittal plane. In the frontal plane, proximal joint abductor moments maintained lateral stability and were larger at the hip in older adults. Understanding age-related alterations in movement control during functional tasks can help inform the rehabilitation management and assessment of patient populations.