Force-velocity profiling in older adults: An adequate tool for the management of functional trajectories with aging.

INTRODUCTION: The actual mechanisms leading to a reduced muscle power and functional ability in older adults are poorly understood. We investigated the association between different force-velocity (F-V) profiles and impaired muscle power, physical and cognitive function, frailty, and health-related quality of life (HRQoL) in older people.

METHODS: Physical function (habitual gait speed, timed up-and-go test, sit-to-stand and stair-climbing ability), cognitive function, HRQoL and frailty were evaluated in 31 older subjects (70-85 years). The F-V relationship and maximal muscle power (Pmax ) were assessed in the leg press exercise. The skeletal muscle index (SMI) and fat index, moderate-to-vigorous physical activity (MVPA) and sedentary time were obtained from DXA scans and accelerometry, respectively.

RESULTS: While some subjects showed a force deficit (FDEF ), others presented a velocity deficit (VDEF ), both leading to an impaired muscle power [Effect size (ES) = 1.30-1.44], and to a likely-very likely moderate harmful effect in their physical and cognitive function, HRQoL and frailty levels (except the VDEF group for cognitive function) [ES = 0.76-1.05]. Leg muscle mass and specific force were similarly associated with force at Pmax , while MVPA but not sedentary time was related to fat index, force at Pmax , and power values (all p < 0.05). A trend was found for the negative association between fat index and relative Pmax (p = 0.075).

CONCLUSION: Older subjects exhibited different mechanisms (force vs. velocity deficits) leading to impaired muscle power. Both deficits were associated with a lower physical function and quality of life, and a higher frailty, whereas only a force deficit was associated with a lower cognitive function. Interventions aimed at reversing age- and/or disuse-related impairments of muscle power might evaluate the specific responsible mechanism and act accordingly.