The effect of exercise on brain function in people with stroke

Neuroplasticity as measured by a non-invasive brain stimulation paradigm. Neuroplasticity will be quantified as the effect of iTBS by measuring motor evoked potentials (MEPs) from the first dorsal interosseous (FDI) muscle. Stimulation was delivered using a Neuro-MS/D rTMS device (Neurosoft Ltd. Ivanova, Russia) that was connected to an oil cooled figure eight coil (wing diameter 70mm). Single pulses were delivered every five seconds to the contralesional motor cortex region. The coil was held tangentially to the scalp with the handle positioned at a 45-degree posterolateral angle. The optimal position (over the scalp) for evoking MEPs in the resting FDI muscle was located by systematically moving the coil in small increments, then marked with a permanent marker to ensure consistency for subsequent stimulation. An automated algorithm obtained RMT, defined as the lowest stimulus intensity to evoke a MEP of 0.05mV in the relaxed FDI muscle in at least 5 out of 10 consecutive stimulations. Corticospinal excitability was measured by recording MEPs at 120% RMT and measuring peak-to-peak amplitudes. Blocks of 20 MEPs were completed at each time point (pre-activity (exercise/control), post-activity (exercise/control), 0 minutes post-iTBS, 5 minutes post-iTBS, 10 minutes post-iTBS and 15 minutes post-iTBS) to ensure reliability of MEP amplitude. The FDI was chosen to avoid any potential effect of fatigue on the muscle’s response to stimulation, as it was not directly involved in exercise during the intervention.

The aim of this pilot study is to investigate whether moderate intensity exercise could increase neuroplasticity in people with chronic stroke. We specifically investigated people with chronic stroke to avoid the initial, brief, spontaneous period of enhanced neuroplasticity that emerges early after stroke. To evaluate capacity for neuroplasticity, we used a repetitive stimulation protocol, known as intermittent theta-burst stimulation (iTBS) which has been shown to modulate the efficiency of synapses within the cortex. Physiologically, this can be quantified as a change in cortical excitability. Therefore, the hypothesis was that if moderate intensity exercise increases capacity for neuroplasticity, then the physiological response to iTBS would be greater compared to people who do not undertake exercise. If moderate intensity exercise does increase neuroplasticity in people with stroke, then it might provide one method to explore as a technique to re-open a period of enhanced neuroplasticity. Future trials could use exercise as a brain priming therapy to increase responsiveness to rehabilitation.