High-intensity Aerobic Exercise Blocks the Facilitation of iTBS-induced Plasticity in the Human Motor Cortex

Acute exercise studies using transcranial magnetic stimulation (TMS) can provide important insights into the mechanisms underpinning the positive relationship between regular engagement in physical activity and cortical neuroplasticity. Emerging evidence indicates that a single session of aerobic exercise can promote the response to an experimentally induced suppressive neuroplasticity paradigm; however, little is known about the neuroplasticity response to facilitatory paradigms, including intermittent theta burst stimulation (iTBS). To more fully characterize the effects of exercise on brain plasticity we investigated if a single 30 min bout of high-intensity cycling (80% predicted heart rate reserve) modulated the response to an iTBS paradigm compared to rest. In 18 participants (9 females; 25.5 ± 5.0 years, range: 18-35 years) iTBS was applied using standard repetitive transcranial magnetic stimulation techniques immediately following exercise or 30 min of rest. Motor evoked potentials (MEPs) were recorded from the right first dorsal interosseous muscle at baseline, after the exercise/rest period but before iTBS, and at 5 time points following iTBS (0, 5, 10, 20 and 30 min). Contrary to our hypothesis, MEPs were suppressed following iTBS after a single 30 min bout of lower limb aerobic exercise compared to rest. These results indicate that acute aerobic exercise may not always enhance the response to an experimentally induced neuroplasticity paradigm. Further investigation of the factors that influence the relationship between exercise and neuroplasticity is warranted.