Moderate intensity aerobic exercise may enhance neuroplasticity of the contralesional hemisphere after stroke: a randomised controlled study

Abstract

Upregulation of neuroplasticity might help maximize stroke recovery. One intervention that appears worthy of investigation is aerobic exercise. This study aimed to determine whether a single bout of moderate intensity aerobic exercise can enhance neuroplasticity in people with stroke. Participants were randomly assigned (1:1) to a 20-min moderate intensity exercise intervention or remained sedentary (control). Transcranial magnetic stimulation measured corticospinal excitability of the contralesional hemisphere by recording motor evoked potentials (MEPs). Intermittent Theta Burst Stimulation (iTBS) was used to repetitively activate synapses in the contralesional primary motor cortex, initiating the early stages of neuroplasticity and increasing excitability. It was surmised that if exercise increased neuroplasticity, there would be a greater facilitation of MEPs following iTBS. Thirty-three people with stroke participated in this study (aged 63.87 ± 10.30 years, 20 male, 6.13 ± 4.33 years since stroke). There was an interaction between Time*Group on MEP amplitudes (P = 0.009). Participants allocated to aerobic exercise had a stronger increase in MEP amplitude following iTBS. A non-significant trend indicated time since stroke might moderate this interaction (P = 0.055). Exploratory analysis suggested participants who were 2-7.5 years post stroke had a strong MEP facilitation following iTBS (P < 0.001). There was no effect of age, sex, resting motor threshold, self-reported physical activity levels, lesion volume or weighted lesion load (all P > 0.208). Moderate intensity cycling may enhance neuroplasticity in people with stroke. This therapy adjuvant could provide opportunities to maximize stroke recovery.

Figure 1

Experimental protocol. Following screening and randomization, procedures are shown with top describing the intervention arm, and bottom the control arm. Abbreviations: iTBS, intermittent theta burst stimulation; MEPs, motor evoked potentials.

Figure 2

Individual MRI data showing level of greatest cross-sectional area of lesion. Lesion is shown in red.

Figure 3

Effect of exercise on iTBS response. X-axis shows time that motor evoked potentials were recorded, and Y-axis provides motor evoked potentials normalized to baseline (values > 1 indicate facilitation of motor evoked potentials by iTBS). Error bars are shown as shaded regions (SEM). The exercise condition appeared to promote a stronger facilitation of motor evoked potentials following iTBS. Abbreviations: iTBS, intermittent theta burst stimulation.

Figure 4

Exploration of the effect of time since stroke on modifying iTBS response following exercise. Top figures show grand average iTBS responses on the Y-axis (values > 1 indicate facilitation of motor evoked potentials by iTBS) and time since stroke on the X-axis for exercise and control groups respectively. For the exercise group (A), a hierarchical cluster analysis identified three distinct groupings in the data (shown as orange, black and blue data points). For the control group (B), a hierarchical cluster analysis identified two distinct groupings (shown as black and orange data points). Based on cluster analysis, iTBS responses were separated into 0–2 years post-stroke, 2–7.5 years post-stroke and > 7.5 years post-stroke for the exercise group. For the control group, data were separated as 0–8 years post-stroke and > 8 years post-stroke. Bottom figures show effect of exercise (C) or control (D) on iTBS response. Group averages are shown as per Fig. 3, with data further separated out based on time since stroke in determined by cluster analysis. It appeared that participants who were 2–7.5 years post stroke (black line) exhibited a stronger iTBS response following exercise. Error bars are SEM. Abbreviations: iTBS, intermittent theta burst stimulation.