Abstract:
This study evaluated sex-related differences in the tibialis anterior (TA) surface
electromyography (EMG) to force relationship. One-hundred participants (50 males and
50 females) performed three isometric contractions at 20, 40, 60, 80, and 100% of
maximal voluntary contraction (MVC) in an apparatus designed to isolate the action of
the dorsiflexors. The surface EMG signal was amplified (lOOOx), band-pass filtered
(10-500Hz), and sampled at 2048 Hz. The load cell signal was low-passed filtered at
100 Hz and sampled at the same rate. Males were stronger than females {P <0.05).
However, there was no significant difference in root-mean-square (RMS) values between
sexes {P <0.05). Both sexes exhibited a quadratic increase in RMS across force levels (P
<0.05). The mean power frequency (MNF) for males was greater than for females {P
<0.05). Males and females exhibited a linear increase in both frequency measures up to
80% of MVC (P <0.05). Between 80 and 100% MVC, the frequency values for the
females plateaued while males showed a decrease {P <0.05). The magnitude of the
difference in MNF between males and females was consistent with sex-specific TA
physiology. In general, the pattern of means for RMS and MNF between males and
females revealed no sex-related differences in the surface EMG/force relationship. We
therefore conclude that there are no sex-related differences in the gradation of muscle
force.
