Motor cortex plasticity is greater in endurance-trained cyclists following acute exercise

Previous research using transcranial magnetic stimulation (TMS) has shown that plasticity within primary motor cortex (M1) is greater in people who undertake regular exercise, and a single session of aerobic exercise can increase M1 plasticity in untrained participants. This study aimed to examine the effect of an acute bout of exercise on M1 plasticity in endurance-trained (cyclists) and untrained individuals. Fourteen endurance-trained cyclists (mean ± SD; 23 ± 3.8 yr) and 14 untrained individuals (22 ± 1.8 yr) performed two experimental sessions. One session included an acute bout of high-intensity interval training (HIIT) exercise involving stationary cycling, whereas another session involved no-exercise (control). Following exercise (or control), I-wave periodicity repetitive TMS (iTMS) was used (1.5-ms interval, 180 pairs) to induce plasticity within M1. Motor evoked potentials (MEPs) induced by single and paired-pulse TMS over M1 were recorded from a hand muscle at baseline, after HIIT (or control) exercise and after iTMS. Corticospinal and intracortical excitability was not influenced by HIIT exercise in either group (all P > 0.05). There was an increase in MEP amplitude after iTMS, and this was greater after HIIT exercise (compared with control) for all subjects (P < 0.001). However, the magnitude of this response was larger in endurance cyclists compared with the untrained group (P = 0.049). These findings indicate that M1 plasticity induced by iTMS was greater in endurance-trained cyclists following HIIT. Prior history of exercise training is, therefore, an important consideration for understanding factors that contribute to exercise-induced plasticity.NEW & NOTEWORTHY We use a novel form of repetitive transcranial magnetic stimulation to show that motor cortex plasticity is increased after acute exercise and that this effect is bolstered in endurance-trained cyclists. These findings indicate that participation in regular endurance exercise (involving lower limb muscles) has widespread effects on cortical plasticity (assessed in unexercised upper limb muscles) following acute lower-limb cycling exercise. It also highlights that exercise history is an important factor in exercise-induced cortical plasticity.