Pitching-specific facilitation of upper-limb corticospinal excitability during motor imagery of sports motor skills

Pitching is an essential skill in baseball, requiring precise and well-coordinated neural control. However, elucidating its underlying neural mechanisms remains challenging because of the methodological difficulties in assessing neural activity during dynamic movement. Motor imagery (MI) provides a potential approach for investigating neural control in pitching, as MI of basic movements activates neural processes similar to those during actual movement. This study examined how MI of pitching, with and without visual guidance, modulates corticospinal excitability in muscles involved in pitching. Electromyographic activity was recorded from the flexor carpi radialis (FCR), extensor carpi radialis, first dorsal interosseous, and abductor pollicis brevis (APB) muscles. Corticospinal excitability was evaluated by motor-evoked potential (MEP) amplitudes, elicited by transcranial magnetic stimulation to the primary motor cortex. MEPs were measured during kinesthetic MI across five sports skills, using only MI in Experiment 1 and using MI with a model video (vMI) in Experiment 2. Results showed that both types of baseball-MI significantly facilitated corticospinal excitability in APB, and baseball-vMI significantly facilitated corticospinal excitability in FCR, but not in other recorded muscles compared with those at rest. These results likely reflect the relative contribution and functional role of each muscle and fine motor control in actual pitching. The facilitation in APB was specific to baseball-MI/vMI, and this specificity is further supported by the findings that each sport's MI/vMI selectively facilitated corticospinal excitability in the muscle involved in the imagined movements. These findings provide foundational knowledge and a methodology for investigating the modulation of corticospinal excitability during pitching.