Relationship between surface EMG and force with skin cooling in the tibialis anterior

抄録

  The purpose of this study was to examine changes in muscle activation with skin cooling (SC) to determine the optimal levels of force at which skin cooling has an effect on the recruitment of fast twitch muscle fiber. Subjects performed an isometric dorsiflexion with SC and without SC at 10%, 20%, 30%, 40%, 50%, 60%, and 70% of maximal voluntary contraction, in random order. Surface electromyography (EMG) were obtained from the tibialis anterior muscle. Skin temperature was maintained at 25℃ using a gel-cooling pad. Muscle temperature did not change with skin cooling. The root mean square of the EMG (rmsEMG) with SC was significantly greater than without SC in contractions from 10% to 50% MVC. Skin cooling displayed significantly lower mean power frequency (MPF) values than without SC at the seven different force levels. Changes in rmsEMG and MPF may indicate a reduction in the threshold of high threshold motor units (HT-MUs), along with inhibition of low threshold motor units (LT-MUs) and substitution of LT-MUs with HT-MUs. We propose that skin cooling can be used as a form rehabilitative training, optimally targeting the recruitment of fast twitch muscle fiber.