Author(s): YAMASAKI, D., KANEKO, N., KATO, T., MASHIKI, Y., NAKAZAWA, K., Institution: THE UNIVERSITY OF TOKYO, Country: JAPAN, Abstract-ID: 624

INTRODUCTION:
Motor imagery (MI) is the mental simulation of a movement without any physical output. MI has been applied to sports training because MI induces neural activities similar to those during actual motor execution. However, many studies of MI have focused on basic movements such as single-joint movements or gait, and there are limited findings about neural mechanisms during MI of sports skills. Knowledge of neural mechanisms during MI of sports skills is needed to establish efficient imagery training. Therefore, we aim to examine the effects of various sports skill’s MI on corticospinal excitability of the upper limb muscles.
METHODS:
Twelve healthy males participated in this study. Electromyographic activity was recorded from the flexor carpi radialis (FCR), extensor carpi radialis (ECR), first dorsal interosseous (FDI), and abductor pollicis brevis (APB) muscles of the dominant hand. Transcranial magnetic stimulation (TMS) was applied over the primary motor cortex of the contralateral side of the dominant hand, and motor evoked potentials (MEPs) induced by TMS were used for assessing corticospinal excitability. MEPs were recorded under the following conditions: a) rest condition and b) MI condition. In the MI condition, subjects performed 5 imagery tasks: 1) baseball pitching (baseball-MI), 2) tennis serving (tennis-MI), 3) volleyball serving (volleyball-MI), 4) basketball free-throw (basketball-MI), and 5) soccer shooting (soccer-MI). All tasks except basketball-MI were imagined as full strength. We compared MEP amplitudes between the rest condition and MI condition (normalized by MEP amplitudes of the rest condition).
RESULTS:
The MEP amplitudes of APB were significantly increased in the baseball-MI (p<0.05) compared with those in the rest condition. The MEP amplitudes of FCR were significantly increased in the tennis-MI and volleyball-MI (p<0.05) compared with those in the rest conditions. However, there was no significant increase of MEP amplitudes of any muscles in the basketball- and soccer-MI.
CONCLUSION:
Significant facilitation in corticospinal excitability of APB occurred only in the baseball-MI, not in all other MI conditions. These results would be related to the fine motor skills in the hand muscles for baseball pitching. Although fine motor skills are involved in basketball free-throw, corticospinal excitability in the basketball-MI did not increase. This difference may be due to the intensity in the upper limb muscles for performing the imagined movement. Corticospinal excitability in FCR was significantly facilitated in the tennis-MI and volleyball-MI, which use forearm muscles as a prime mover. Furthermore, there were no significant changes in corticospinal excitability in the soccer-MI, which mainly involves the lower limbs. The observed differences in the corticospinal excitability of upper-limb muscles during MI of various sports skills would be considered to reflect the motion characteristics of each sport skill.