Influence of gender on the EMG power spectrum during an increasing force level.

The aim of the present study was to contrast, between men and women, the behavior of EMG power spectrum statistics (median frequency (MF) and mean power frequency (MPF) obtained across increasing force levels. Thirteen men and sixteen women produced ramp (single contractions with the force increasing linearly) elbow flexions and extensions from 0 to 100% of the maximum voluntary contraction (MVC). Each ramp was produced in a 5-s period. Surface EMG signals from triceps brachii (TB), anconeus (AN), and biceps brachii (BB) were recorded with miniature surface electrodes placed 6 mm apart. These signals were sampled at 2,000 Hz. The MPF and MF of power spectra, obtained from single 256-ms windows, were computed for each muscle at 10, 20, 40, 60, and 80% MVC. Significant differences (two-way analyses of variance (ANOVAs); p < 0.05) in the behaviors of the MPF and MF across force levels were found between men and women. In general, the MPF and MF showed more pronounced increases across increasing force levels for men than for women. It is proposed that this gender effect could be explained by differences in skinfold thickness and fiber type characteristics between the two groups of subjects.