Thomas J. O’Leary

Sex differences in neuromuscular fatigability in response to load carriage in the field in British Army recruits

OBJECTIVES Women are resistant to neuromuscular fatigue compared to men in response to a range of exercise tasks. The sex differences in the neuromuscular responses to load carriage have yet to be investigated. DESIGN Prospective cohort study. METHODS Twenty-three male and 19 female British Army recruits completed a 9.7km loaded march within 90min, with the weight carried dependent on military trade (16±2kg for men and 15±1kg for women). Isometric maximal voluntary contraction (MVC) force of the knee extensors and vertical jump (VJ) height were examined pre- and post-loaded march to examine neuromuscular fatigue. Heart rate (HR) was recorded throughout and ratings of perceived exertion (RPE) was recorded following the march. RESULTS HR was higher for women (173±9bmin-1, 83±6% heart rate reserve) than men (158±8bmin-1, 72±6% heart rate reserve) (p≤0.001). RPE following the march was also higher for women than men (6±2 vs 4±2, respectively, p<0.001). The loss in MVC force was greater for men than women (-12±9% vs -9±13%, respectively, p=0.031), however VJ height was impaired to a similar extent (-5±11% vs -5±6%, respectively, p=0.582). CONCLUSIONS The greater physiological stress during load carriage for women compared to men did not translate to a greater severity of knee extensor muscle fatigue, with women demonstrating fatigue resistance.