Changes in lower extremity peak angles, moments and muscle activations during stair climbing at different speeds.

Stair climbing is a common daily activity, yet there is no basic knowledge on how lower extremity joint angles, moments or muscle activations are affected by stair climbing speed. This information will determine whether speed matching is necessary for stair climbing studies. Moreover, changes in lower extremity biomechanics during stair climbing at different speeds will aid in the clinical interpretation of a patient's maximal stair climbing speed. Thirty healthy participants provided consent. Kinematics, kinetics, and muscle activations were collected on a three step staircase. Subjects climbed the staircase at normal, slow and fast self-selected speeds. Linear mixed models for repeated measures were used to study the associations between speed and the lower extremity peak joint angles and moments, and muscle activations. The peak hip flexion and extension moments increased with increasing speed, while peak knee flexion moment did not vary consistently with speed. The peak muscle activations varied consistently with respect to the sagittal plane kinetics. These results suggest that in healthy subjects, the hip is the greatest contributor when modulating stair climbing speed, while additional knee contributions do not appear necessary to increase speed. Further stair studies should consider speed matching in order to accurately assess biomechanical differences.