Effect of simple motor exercise on motor adaptation in complex dynamic tasks: exploring age-related variations.

Dexterous manual actions rely on the integration of precise sensorimotor control and adaptive learning. However, it remains unclear how repetition of simple motor tasks influences subsequent adaptation to force perturbations in a dynamic manipulation task. This study examined whether different types of motor repetition, force-based or movement-based, affect the adaptation process in young and older adults. Sixty right-handed participants (30 young and 30 older) performed a dynamic manipulation task using a robotic interface, where they had to counteract perturbation torques during a handle-lifting movement. Before the perturbation trials, participants engaged in either force repetition, which required producing discrete isometric torque pulses, or movement repetition, which involved continuous wrist rotations. We found that young adults who performed force repetition exhibited enhanced adaptation in the dominant hand, whereas movement repetition did not yield the same benefit. However, older adults showed no significant modulation of adaptation based on repetition type. In addition, across all participants, adaptation performance differed between supination and pronation directions, with greater accuracy observed in the supination condition. This asymmetry was more pronounced in young adults and in the nondominant hand. These findings suggest that the benefits of force repetition for predictive motor control may depend on both age and limb dominance, with implications for motor training and rehabilitation strategies.