Tadayuki Tokunaga

Effect of stimulation of cold receptors with menthol on EMG activity of quadriceps muscle during low load contraction

Abstract Purpose: Facilitatory and inhibitory responses of spinal motor neurons are influenced by somatosensory input from the skin. The purpose of this study, employing electromyography, was to examine the neuromuscular changes that occur with menthol applied to the skin over the quadriceps muscle. Methods: Forty-two healthy volunteers performed isometric knee extensions at 35% maximum voluntary contraction (MVC) in three groups (Adult Placebo, Adult Menthol, Older Adult Menthol). Stimulation used was application of 5% menthol gel to the skin. Surface electromyography (sEMG) from the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) was recorded using miniature pair electrodes. Results: Root mean square electromyography (rmsEMG) in VL and VM significantly increased with menthol stimulation both in Adult and Older Adult, but no significant difference was observed between Adult Menthol and Older Adult Menthol. There was a significant decrease in mean power frequency (MPF) in VM with menthol stimulation in Older Adult, but no significant changes were observed in Adult Menthol. Conclusion: Neuromuscular modulation was observed with the application of menthol gel at low loads in the present study. These findings could lead to a new method of muscular training that targets the recruitment of fast type muscle safe for older adults.