Is the Ability to Maximally Activate the Dorsiflexors in Men and Women Affected by Indwelling Electromyography Needles?

Brown RE, Bruce SH, Jakobi JM. Is the ability to maximally activate the dorsiflexors in men and women affected by indwelling electromyography needles? Arch Phys Med Rehabil 2009;90:2135-40, Objectives: To determine whether maximal force is similar between conditions with and without a microelectrode, and to evaluate potential sex differences when using invasive procedures. Design: Crossover trial. Setting: University laboratory. Participants: Young men (n=8; mean +/- SD age, 20.3 +/- 2.0y) and young women (n=8; mean age +/- SD, 19.8 +/- 0.4y). Interventions: Not applicable. Main Outcome Measures: Subjects randomly performed 5 ankle dorsiflexion maximal voluntary contractions (MVCs) with an indwelling microelectrode in the tibialis anterior and 5 MVCs with the twitch interpolation technique without a microelectrode. Strength and contractile properties were measured. No visual or oral feedback was provided. When the greatest MVCs from each condition differed by more than 5%, 3 additional attempts were given with feedback in the lesser of the 2 conditions. Results: Men were similar to 39% stronger than women, and contractile properties were similar to 11% faster, but maximal voluntary activation was similar between sexes (similar to 95%). However, in men and women, the greatest MVC did not differ between the microelectrode and activation conditions (P=.87). In 9 of the 16 subjects, MVC was about 5% less in 1 of 2 conditions. Five of these 9 subjects were able to match or exceed their highest MVC with the aid of visual feedback. Conclusions: This suggests that muscle strength and contractile properties differ between men and women. Indwelling microelectrodes do not hinder the ability to achieve MVC, but adequate feedback is necessary to achieve the highest force.