High-velocity resistance training improves the force-velocity profile in middle-aged and older adults.

The main goal of the present study was to examine the effects of a high-velocity resistance training (HVRT) program on the force-velocity (F-V) profile of different groups of aging adults. An additional aim was to explore whether individual baseline F-V profiles were associated with training-induced improvements in muscle power and functional capacity. Middle-aged and older adults with and without mobility limitations (n = 36, 61 ± 13 years) completed a 12-week HVRT program (2 days/week, 40-60% 1-RM). F-V profiles were determined using leg press exercises at loads ranging from 30-90% 1-RM, and a linear position transducer. Functional capacity was assessed via maximal gait speed and 30-s Sit-to-Stand tests. HVRT significantly increased the theoretical maximal force (F0), maximal power (Pmax), and the F-V slope (all p < 0.001), while maximal movement velocity (V0) remained unchanged at the group level. Analysis of individual trajectories revealed substantial heterogeneity in F-V adaptations. Lower baseline V0 was associated with greater improvements in V0 (r = -0.629, p < 0.001), and this association was attenuated in an Oldham-style sensitivity analysis (r = -0.366, p = 0.028). Stratification by V0 tertiles showed that velocity-deficient individuals had lower baseline power but experienced the greatest V0 gains (+ 10.6% vs. -1.0%, p = 0.002). Within this subgroup, improvements in V0 were associated with improvements in maximal gait speed (r = 0.685, p = 0.010). These findings suggest that, in the present sample, HVRT enhances muscle power primarily via force-related adaptations, while velocity-related adaptations were heterogeneous and may be functionally relevant when they occur.