Effectiveness of muscle vibration in modulating corticospinal excitability.

This study explored the effect of vibration of the forearm extensors on motor cortical excitability and the influence of stimulus duration. Sixteen healthy volunteers between 23 and 42 years old participated in one or two studies. We applied 15 or 30 min of 100 Hz, 0.5 mm-amplitude vibration to the extensor carpi radialis longus (ECRL) muscle. Cortical excitability was measured as the magnitude of the motor-evoked potentials (MEPs), and the size of the representation area associated with ECRL and flexor carpi ulnaris muscles was determined with the use of transcranial magnetic stimulation. A 33% increase in MEP size and enlarged area of cortical excitability was detected 5 min after 15 min of vibration in the ECRL only. No changes were associated with 30 min of vibration in either muscle. These findings indicate that the facilitatory effects of vibration in healthy subjects depend on stimulus duration and provide impetus for testing the extent to which short-duration vibration augments corticospinal excitability to improve muscle function in people with central motor disorders.