Effects of an acute bout of moderate-intensity aerobic exercise on motor learning and neuroplasticity. (2015)
Aerobic exercise has been promoted as a possible adjunct therapy to neurorehabilitation practice, given its positive effects on brain health. In healthy young adults, acute high-intensity cycling can enhance motor performance and learning of a complex motor task, and promote neuroplasticity in the motor system. However, clinical populations may not be able to participate in high-intensity exercise. To date there is inconsistent evidence for the efficacy of moderate-intensity aerobic exercise to alter motor learning and neuroplasticity in healthy young adults. Using two experiments, we aimed to determine how acute moderate-intensity cycling affects motor behavior and neuroplasticity in healthy young individuals. First, 16 participants practiced a complex motor skill after 30 minutes of moderate-intensity cycling or seated rest, on separate occasions. Motor performance was assessed at baseline, immediately after, and 5 minutes after exercise or rest. Twenty-four hours later, we assessed motor learning at a no-exercise retention test. Under the exercise condition, participants maintained performance over time, whereas, performance diminished over time under the rest condition, and became worse than post-exercise performance. Conditions did not differ at retention. Second, another group of 16 participants underwent paired associative stimulation (PAS) a transcranial magnetic stimulation (TMS) protocol known to induce neuroplasticity in the motor system. Effects of PAS were separately compared after a 30-minute bout of moderate-intensity cycling versus seated rest. At baseline, immediately after PAS, and 30 minutes post-PAS, we measured corticomotoneuronal excitability and excitability of intracortical neural circuits using TMS. We found that PAS increased corticomotoneuronal excitability when performed after exercise, but not rest. Exercise and PAS modulated activity in specific neural circuits post-intervention, without similar results under the rest condition. Moderate-intensity aerobic exercise can promote neuroplasticity in the motor system, but in this study similar effects did not transfer to behavioral measures of motor learning. In order to evaluate the clinical feasibility of this pairing moderate intensity exercise with skilled motor practice, we must first elucidate the dose-response effects of exercise on motor behavior, explore timing effects of exercise on motor learning, and examine how long-term pairing of exercise with practice impacts motor learning.