Five-Time Sit-To-Stand Lower Limb Muscle Power in Older Women: An Explorative, Descriptive and Comparative Analysis.

Background: Muscle power assessment entails the use of complex equipment which impacts its clinical applicability. Recently, equations to estimate lower-limb muscle power measures based on 5-repetition sit-to-stand (5STS) performance and anthropometric parameters were validated. However, their ability to discriminate physical performance status in older adults is still unknown. Moreover, the analysis of the biomechanical aspects of 5STS might represent a valid instrument to identify people with different physical statuses.

Objectives: Explore and examine the biomechanical aspects of 5STS performance, and compare the capacity of this measure and 5STS muscle power equations to discriminate older women with different physical function levels.

Design: Cross-sectional study.

Setting: Community.

Participants: Older women.

Measurements: 5STS using a linear encoder, Timed "Up-andGo" (TUG), isometric handgrip strength (IHG) and walking speed (WS).

Results: Results from ANOVA analysis indicated that peak concentric muscle power was reached in the first 5STS repetition and then declined significantly (P= 0.006). When participants were divided in high and low physical performance groups according to median results of TUG, IHG and WS tests, significant differences in 5STS biomechanical aspects were observed, according to independent t-test results (P< 0.05). However, no differences were found for 5STS muscle power equations. Pearson's correlation analysis indicated that 5STS biomechanical aspects (P< 0.05), but not 5STS muscle power equations, were significantly associated with physical performance.

Conclusion: Findings of the present study suggest that 5STS biomechanical aspects might contribute to discriminating older women with high and low physical performance.