Sit-to-stand performance depends on sensation, speed, balance, and psychological status in addition to strength in older people

Background. Sit-to-stand (STS) performance is often used as a measure of lower-limb strength in older people and those with significant weakness. However, the findings of recent studies suggest that performance in this test is also influenced by factors associated with balance and mobility. We conducted a study to determine whether sensorimotor, balance, and psychological factors in addition to lower-limb strength predict sit-to-stand performance in older people. Methods. Six hundred and sixty nine community-dwelling men and women aged 75-93 years (mean age 78.9, SD = 4.1) underwent quantitative tests of strength, vision, peripheral sensation, reaction time, balance, health status, and sit-to-stand performance. Results. Many physiological and psychological factors were significantly associated with sit-to-stand times in univariate analyses. Multiple regression analysis revealed that visual contrast sensitivity, lower limb proprioception, peripheral tactile sensitivity, reaction time involving a foot-press response, sway with eyes open on a foam rubber mat, body weight, and scores on the Short-Form 12 Health Status Questionnaire pain, anxiety, and vitality scales in addition to knee extension, knee flexion, and ankle dorsiflexion strength were significant and independent predictors of STS performance. Of these measures, quadriceps strength had the highest beta weight, indicating it was the most important variable in explaining the variance in STS times. However, the remaining measures accounted for more than half the explained variance in STS times. The final regression model explained 34.9% of the variance in STS times (multiple R = .59). Conclusions. The findings indicate that, in community-dwelling older people, STS performance is influenced by multiple physiological and psychological processes and represents a particular transfer skill, rather than a proxy measure of lower limb strength.