Sit-to-stand muscle power test: Comparison between estimated and force plate-derived mechanical power and their association with physical function in older adults

Objectives: This study aimed i) to assess the assumptions made in the sit-to-stand (STS) muscle power test [body mass accelerated during the ascending phase (90% of total body mass), leg length (50% of total body height) and concentric phase (50% of total STS time)], ii) to compare force plate-derived (FPD) STS power values with those derived from the STS muscle power test; and iii) to analyze the relationships of both measurements with physical function. Material and methods: Fifty community-dwelling older adults (71.3 +/- 4.4 years) participated in the present investigation. FPD STS power was calculated as the product of measured force (force platform) and velocity [difference between leg length (DXA scan) and chair height, divided by time (obtained from FPD data and video analysis)], and compared to estimated STS power using the STS muscle power test. Physical function was assessed by the timed-up-and-go (TUG) velocity, habitual gait speed (HGS) and maximal gait speed (MGS). Paired t-tests, Bland-Altman plots and regressions analyses were conducted. Results: Body mass accelerated during the STS phase was 85.1 +/- 3.8% (p < 0.05; compared to assumed 90%), leg length was 50.7 +/- 1.3% of body height (p < 0.05; compared to 50%), and measured concentric time was 50.3 +/- 4.6% of one STS repetition (p > 0.05; compared to assumed 50%). There were no significant differences between FPD and estimated STS power values (mean difference [95% CI] = 6.4 W [-68.5 to 81.6 W]; p = 0.251). Both FPD and estimated relative (i.e. normalized to body mass) STS power were significantly related to each other (r = 0.95 and ICC = 0.95; p < 0.05) and to MGS and TUG velocity after adjusting for age and sex (p < 0.05). Conclusions: Estimated STS power was not different from FPD STS power and both measures were strongly related to each other and to maximal physical performance.

Automated summary

The study evaluated the assumptions in the sit-to-stand (STS) muscle power test, compared force plate-derived (FPD) STS power values with those derived from the STS muscle power test, and analyzed the relationships of both measurements with physical function. The findings showed that estimated STS power was not significantly different from FPD STS power, and both measures were strongly related to each other and to maximal physical performance.