Lower-limb rate of torque development, but not peak torque, is associated with balance performance in older adults with and without Parkinson’s disease: a cross-sectional study

Abstract Background Aging and Parkinson’s disease (PD) are associated with impairments in rapid force production, physical function, and postural control. However, limited evidence exists regarding the relationship between lower-limb rate of torque development (RTD), physical function, and objective balance measures in older adults with and without PD. This study aimed to evaluate lower-limb peak torque and RTD during an isometric leg press task and investigate their relationship with physical function and balance. Methods This cross-sectional observational study included 20 older adults with PD (PDG) (71.7 ± 8.2 years; Hoehn and Yahr stages I–III) and 20 older adults without PD (CG) (68.2 ± 5.6 years). Peak torque and RTD were assessed using an isometric horizontal leg press with a load cell. Physical function was evaluated using the Short Physical Performance Battery (SPPB), Timed Up and Go test (TUG), and walking speed test. Static and dynamic balance were assessed using a force platform. Multiple linear regression analyses were performed to investigate associations among neuromuscular, functional, and balance variables. Results When compared with the CG, the PDG demonstrated lower RTD200 ( p = 0.022), poorer physical function (SPPB: p = 0.004; TUG: p = 0.002; walking speed: p = 0.001), and greater postural sway during static balance assessment, including greater mediolateral displacement ( p = 0.001), anteroposterior displacement ( p = 0.023), and 95% confidence ellipse area ( p = 0.005). RTD variables showed stronger associations with balance outcomes than peak torque. Higher RTD200 was associated with better static balance performance, while RTD measures were also associated with dynamic balance variables. In the PDG, higher peak torque was associated with lower motor impairment, whereas shorter disease duration and lower disease stage were associated with higher RTD50. Conclusion Older adults with PD exhibited lower RTD200, poorer physical function, and greater postural instability than controls. RTD showed stronger associations with balance variables than peak torque, suggesting that rapid force production may be an important neuromuscular parameter related to postural control and functional performance in older adults with and without PD.