Effects of functional ability and training on chair-rise biomechanics in older adults

Background. Difficulty in rising from a chair is common in older adults and may be assessed by examining the biomechanics of the rise. The purposes of this study were (i) to analyze the biomechanics of rise performance during chair-rise tasks with varying task demand in older adults with varying ris e ability and (ii) to determine whether a strength-training program might i mprove chair-rise success and alter chair-rise biomechanics, particularly u nder situations of increased task demand. Methods. A training group (n = 16; mean age, 82 years) completed a 12-week strength-training regimen while a control group (n = 14 mean age, 84 years) participated in a seated flexibility program. Outcomes included the abilit y to complete seven chair-rise tasks, and. if the chair-rise tasks were suc cessful, the biomechanics of these rises. Chair-rise task demand was increa sed by lowering the seat height. restricting the use of hands, increasing r ise speed, and hunting foot support. Results. At baseline. increased chair-rise task demand generally required i ncreased task completion time, increased anterior center of pressure (COP) placement, increased momentum, increased hip flexion, and increased hip and knee torque output. Those unable to rise at 100% knee height without the u se of their hands (task NH-100), compared with those able to rise during ta sk NH-100, followed this pattern in requiring increased time, more anterior placement of the COP, and increased hip flexion to rise in the least deman ding tasks allowing the use of hands. However, the unable subjects generate d less momentum and knee torque in these tasks. At 12 weeks, and compared w ith baseline and controls, the training group demonstrated changes in chair -rise biomechanics but no significant changes in rise success. The training subjects, as compared with the controls, maintained a more posterior COP, increased their vertical and horizontal momentum, maintained their knees in greater extension. and maintained their knee-torque output. Conclusions. These data demonstrate that subtle yet significant changes can be demonstrated in chair-rise performance as a result of a controlled resi stance-training program. These biomechanical changes may represent a shift away from impairment in chair-rise ability. and, although the changes are s mall, they represent how training may reduce rise difficulty.