Aerobic exercise (AE) and transcranial direct current stimulation (tDCS) are priming techniques that have been studied for their potential neuromodulatory effects on corticomotor excitability (CME); however, the synergistic effects of AE and tDCS are not explored in stroke. Here we investigated the synergistic effects of AE and tDCS on CME, intracortical and transcallosal inhibition, and motor control for the lower limb in stroke. Twenty-six stroke survivors participated in 3 sessions: tDCS, AE, and AE+tDCS. AE included moderate-intensity exercise and tDCS included 1 mA of anodal tDCS to the lower limb motor cortex with or without AE. Outcomes included measures of CME, short-interval intracortical inhibition (SICI), ipsilateral silent period (iSP) (an index of transcallosal inhibition) for the tibialis anterior, and ankle reaction time. Ipsilesional CME significantly decreased for AE compared with AE+tDCS and tDCS. No differences were noted in SICI, iSP measures, or reaction time between all 3 sessions. Our findings suggest that a combination of exercise and tDCS, and tDCS demonstrate greater excitability of the ipsilesional hemisphere compared with exercise only; however, these effects were specific to the descending corticomotor pathways. No additive priming effects of exercise and tDCS over tDCS was observed. Novelty: An exercise and tDCS paradigm upregulated the descending motor pathways from the ipsilesional lower limb primary motor cortex compared with exercise. Exercise or tDCS administered alone or in combination did not affect intracortical or transcallosal inhibition or reaction time.
Keywords: aerobic exercise; amorçage cortical; cortical priming; corticomotor excitability; excitabilité corticomotrice; exercice aérobie; reaction time; stimulation transcrânienne en courant continu; temps de réaction; tibial antérieur; tibialis anterior; transcranial direct current stimulation.