Physical Inactivity + tDCS

The purpose of this study is to investigate the influence of a single session of moderate aerobic exercise on motor cortex neuroplasticity in older adults, both alone and in combination with transcranial direct current stimulation (tDCS), and to compare these effects with those observed in young adults. Normal aging is associated with changes in the central nervous system that can affect motor function, sensorimotor integration, and cortical inhibitory mechanisms. These alterations may reduce the brain's capacity for neuroplasticity, which is essential for motor learning and functional adaptation. Physical exercise has been proposed as a potential strategy to counteract age-related decline in neuroplasticity. In this study, healthy young and older adults will participate in three experimental sessions. Participants will complete two experimental conditions in a randomized crossover design: (1) aerobic exercise followed by transcranial direct current stimulation (tDCS), and (2) physical inactivity followed by tDCS and a third session will assess the effects of exercise alone. Moderate aerobic exercise will consist of 20 minutes of cycling on an ergometer. Corticospinal excitability and intracortical and sensorimotor circuit function will be assessed using transcranial magnetic stimulation (TMS) before and after each intervention. Neuroplasticity will be evaluated by measuring changes in motor evoked potentials recorded from a hand muscle of the dominant side. The primary objective is to determine whether aerobic exercise enhances tDCS-induced plasticity, and whether this enhancement differs between young and older adults. Secondary objectives include evaluating age-related differences in intracortical inhibitory and facilitatory mechanisms and sensorimotor integration processes. By improving understanding of how exercise interacts with brain stimulation to modulate motor cortex plasticity, this study may help inform strategies aimed at preserving motor function and functional independence in aging populations.