Modulating Brain Excitability with Cardiovascular Exercise in Chronic Stroke: A Randomized Controlled Trial

BACKGROUND: Corticospinal excitability (CSE) is a surrogate measure of neuroplasticity within the corticospinal tract measured with transcranial magnetic stimulation (TMS). A single bout of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) cardiovascular exercise (CE) have been both demonstrated to transiently augment CSE in people with stroke. However, the effect of multiple sessions of CE and exercise intensity is unknown. OBJECTIVES: We conducted a randomized controlled trial (NCT03614585) to examine the effect of a HIIT vs. MICT CE program on CSE measures obtained using TMS applied on the ipsilesional (ILH) and contralesional (CLH) hemispheres. METHODS: Fifty-six individuals with cortical and/or subcortical stroke lesions in the chronic phase of stroke recovery (>6 months) were randomly assigned to a 12-week HIIT (n = 28) or MICT (n = 28) program. CSE measures were obtained at baseline and post-intervention. Linear mixed model analyses were conducted to compare changes in CSE measures and their respective interhemispheric ratios. RESULTS: CSE changes were not significantly different between HIIT and MICT but exploratory analyses showed that, when analyzed together, both groups increased resting motor evoked potential (MEP) amplitude (P = .003), decreased resting motor threshold (rMT) (P = .030), and reduced intracortical facilitation (ICF) (P = .049) in the ILH. No CSE changes in the CLH were observed. HIIT and MICT rebalanced interhemispheric rMT (P = .020) and ICF ratios (P = .040), and increased resting MEP amplitude ratio (P = .020). CONCLUSIONS: Chronic CE increases excitatory ILH CSE measures and reduces interhemispheric imbalances but intensity does not have a moderating effect. More studies are needed to determine the functional relevance of exercise-induced changes in CSE in post-stroke recovery.