Anodal transcranial direct current stimulation combined with physical exercise increases postural sway in Parkinson’s disease: a double-blind and cross-over study

Transcranial direct current stimulation (tDCS) has shown promising effects on postural control in people with Parkinson’s disease (PwPD). However, the characteristics of the stimulation, such as the specific cortical area targeted and combination with exercise, seem to influence the tDCS effects. Therefore, analyzing these factors is essential for identifying key characteristics and optimizing rehabilitation protocols for postural control in PD.We aimed to analyze the efficacy of tDCS over the primary motor (M1) and pre-frontal cortices (PFC) combined with aerobic exercise on postural control in PwPD. Twenty-one PwPD participated in this crossover, randomized, and double-blind study. The intervention consisted of exercising on a treadmill at moderate intensity for 30 min while receiving the stimulation. tDCS was applied during the central 20 min of exercise over M1, PFC, or sham on 3 different days. Three one-minute trials were conducted with participants standing still on a force platform to assess the center of pressure parameters in anteroposterior (AP) and mediolateral (ML) directions in pre- and post-intervention. Time*stimulation interaction was observed for sway area (p = 0.038) and sway mean amplitude in both the AP (p = 0.009) and ML directions (p = 0.059, marginal effect). Post-hoc analysis indicated a larger sway area and mean amplitude in both directions post-intervention compared to pre-intervention after tDCS application to the M1 and PFC. No significant differences were observed for the sham condition. Our findings suggest that the combination of exercise and tDCS, regardless of the area stimulated, modifies postural control in PwPD, leading to a larger sway.