Sit to stand from progressively lower seat heights -- alterations in angular velocity.

This study investigates the influence of chair height on the dynamics of sit-to-stand for two age groups. Eleven young (25-36 years) and 10 older (61-79 years) adults participated. Subjects rose from chairs set at four heights relative to knee height. Motion was quantified using a bilateral active-marker-based motion analysis system. Subjects appeared to increase trunk flexion angular velocity to overcome mechanical difficulties of decreasing chair heights. This variable showed a main effect for chair height (P = 0.0001). Time at which knee, hip, and trunk extension angular velocity were attained each demonstrated a chair by age interaction effect (P<0.05). Synchrony of body segment maximum extension angular velocities was altered for the older subjects at the lowest chair heights, suggesting that older individuals begin to change their performance as the task becomes more demanding. RELEVANCE:--Sitting to standing is one of the essential physical tasks used frequently throughout the day. Clinicians are frequently called upon to improve chair rise performance for those with functional limitations. Efforts are likely to be most successful if clinicians understand how healthy individuals accommodate to changing conditions (such as changing chair height) and use that information to interpret the performance of those with impairments and functional limitations.