Rate of force development in ankle extensors correlates with performance on functional tests that demand speed and power in older women.

Purpose: Despite the background of decreased ankle extensor muscle strength with aging, there is still debate regarding whether the rate of force development has any relationship with musculoskeletal and functional characteristics. Therefore, we investigated the correlation between the rate of force development (RFD) in ankle extensors during heel rise (HR) and musculoskeletal characteristics and performance in functional tests in community-dwelling older women. Additionally, determine the correlation by decades of age (60-90 years).

Methods: Correlational cross-sectional design analyzed 61 older women (72.8 ± 6.9 years, 29.4 ± 4.9 kg/m²). HR was evaluated on a force platform. In addition, anthropometric, musculoskeletal characteristics, and functional tests were measured. RFD was defined in three-time intervals (0-50 ms, 0-100 ms, and 0-peak). Peak force (Fpeak) and time to peak were also determined. Relative power-STS (STS-power), calf circumference, and skeletal muscle mass were considered musculoskeletal characteristics. Functional tests were timed up-and-go (TUG), walk speed (WS), grip strength, five sit-and-stand (5-STS), sit-and-reach, and single-leg stance.

Results: The RFD and the STS-power were correlated, and the Fpeak with the musculoskeletal characteristics except with the skeletal muscle mass. RFD was correlated with the TUG, WS, and 5-STS, particularly with early RFD (0-50 ms). Oldest old women (80-90 years) only showed correlations between early RFD and the two walk-related tests (TUG and WS), compared to younger old women.

Conclusion: RFD during HR correlates with functional tasks involving ankle extensor's speed and power demands. Impaired RFD of ankle extensors would expose older women to more significant risks of functional loss, especially at older ages.