Sagittal plane center of mass movement strategy and joint kinetics during sit-to-walk in elderly fallers

Biomechanical studies have shown that the horizontal center of mass momentum at seat-off during sit-to-walk is reduced among elderly adults. However, the underlying mechanism of this phenomenon is still lacking. The purpose of this study was to examine differences in center of mass movement strategies and lower extremity joint kinetics in the elderly during sit-to-walk.

Fifteen healthy young adults, fifteen healthy elderly adults (70 years or older) and fifteen elderly fallers performed Timed Up and Go test. Biomechanical data collected from sit-to-walk phase of Timed Up and Go test were analyzed. Outcome measures included center of mass-ankle inclination angles, hip, knee and ankle joint moments, and ground reaction forces of the stance limb.

Results reported here are from 10 participants in each group due to missing force place data. Elderly fallers adopted a movement strategy that included a posterior foot placement at seat-off, a longer duration, and a shorter initial step length. When compared to healthy individuals, elderly fallers demonstrated a greater ankle plantarflexor moment at seat-off.

Increased ankle plantarflexor moment in elderly fallers could be a movement strategy to improve stability during sit-to-walk and may be related to the reduced ankle dorsiflexor strength commonly reported in elderly fallers. Results of this study enhance our understanding on the underlying mechanisms of the altered sit-to-walk movement and could aid in developing effective screening and rehabilitation programs to prevent falling in the elderly.