Lower-Limb muscle power Determines reactive balance stability following Slip-Like perturbations in healthy young and older adults.

Lower-limb muscle power is considered a key determinant of neuromuscular performance, yet its relationship with reactive balance remains poorly understood across the adult lifespan. This study examined the association between countermovement jump (CMJ)-derived peak muscle power and center-of-mass (CoM) stability following a slip-like balance perturbation in young and older adults. Fifty-two healthy adults (27 older, ≥65 years; 25 younger, <65 years) underwent CMJ testing and unexpected platform perturbations. Reactive balance performance was quantified as CoM stability at first post-perturbation touchdown (TD1). Multiple linear regression was used to examine the association between peak muscle power and CoM stability. Secondary exploratory analyses assessed the discriminative capacity of peak muscle power for laboratory-observed falls using logistic regression and receiver operating characteristic (ROC) curve analysis. Peak muscle power was a significant predictor of CoM stability at TD1 (β = 0.013, p < 0.001), explaining 50.1 % of the variance in reactive balance performance (R2 = 0.501). Age group was not an independent predictor once muscle power was accounted for. Participants who experienced a laboratory fall showed substantially lower peak power than non-fallers, and exploratory ROC analysis indicated good discriminative ability (AUC = 0.843), suggesting a preliminary threshold of 26.0 W·kg⁻1. The association between muscle power and reactive balance was consistent across sexes. These findings suggest that neuromuscular capacity is more strongly associated with reactive balance performance than chronological age. CMJ-derived peak power may represent a practical and integrative marker for identifying individuals at heightened risk of balance failure.