Linear- and nonlinear-electromyographic analysis of supracutaneous vibration stimuli of the forearm using diverse frequencies and considering skin physiological properties.

Numerous studies have reported the efficacy of vibration in sensory feedback or substitution devices for users of myoelectric hand prostheses. Although most myoelectric hand prostheses are presently manipulated by a surface electromyogram (sEMG), only a few studies have been conducted on the effect of vibration on an sEMG. This study aimed to determine whether vibration stimulation affects the linear and nonlinear properties of surface electromyography (sEMG) considering the skin properties. The vibration stimuli, with frequencies ranging from 37 to 258 Hz, were applied to the proximal part of the arms of the eight female and seven male subjects. The skinfold thickness, hardness, and vibration threshold at the stimuli loci were measured. The root mean square (rms) and fractal dimension (DF) of the sEMG were measured at a distance of 1 cm in the upward direction from the stimuli loci. Above 223 Hz there were no differences between the rms of the genders in between the vibration stimuli (p > 0.05). Moreover, no differences were observed between the DF of the genders for any frequency (p > 0.05). Above 149 Hz, there were correlations between the rms and the skin hardness in the females. Otherwise, no correlations were observed between the rms and DF and the skin properties in both genders for most of the frequencies (all p > 0.05). These results suggest that vibration stimuli affect the linear properties of the sEMG, but not the nonlinear properties.