Association of Sit-to-Stand Capacity and Free-Living Performance Using Thigh-Worn Accelerometers among 60- to 90-Yr-Old Adults

Purpose Five times sit-to-stand (STS) test is commonly used as a clinical assessment of lower-extremity functional ability, but its association with free-living performance has not been studied. Therefore, we investigated the association between laboratory-based STS capacity and free-living STS performance using accelerometry. The results were stratified according to age and functional ability groups. Methods This cross-sectional study included 497 (63% women) participants aged 60–90 years from three independent studies. A thigh-worn tri-axial accelerometer was used to estimate angular velocity in maximal laboratory-based STS capacity and in free-living STS transitions over 3-7 days of continuous monitoring. Functional ability was assessed with Short Physical Performance Battery (SPPB). Results Laboratory-based STS capacity was moderately associated with the free-living mean and maximal STS performance (r = 0.52 - 0.65, p < .01). Angular velocity was lower in older compared to younger and in low- versus high-functioning groups, both in capacity and free-living STS variables (all p < .05). Overall, angular velocity was higher in capacity compared to free-living STS performance. The STS reserve (test capacity – free-living maximal performance) was larger in younger and in high-functioning compared to older and low-functioning groups (all p < .05). Conclusions Laboratory-based STS capacity and free-living performance were found to be associated. However, capacity and performance are not interchangeable, but rather provide complementary information. Older and low-functioning individuals seemed to perform free-living STS movements at a higher percentage of their maximal capacity compared to younger and high-functioning individuals. Therefore, we postulate that low capacity may limit free-living performance.