Relative strength explains the differences in multi-joint rapid force production between sexes

The primary aim of this study was to determine whether relative strength explains the differences in the rapid force production (force developed during first 150-, 200-, and 250 ms) of females and males, and to evaluate the relationships between peak force and rapid force production. Sixty-three team sport athletes (females: n = 25, age = 21.5 ± 1.3 years, stature = 166 ± 5 cm, body mass = 60.65 ± 10.04 kg; males: n = 38, age = 21.9 ± 1.1 years, stature = 178 ± 7 cm, body mass = 76.55 ± 12.88 kg) performed a series of isometric mid-thigh pull (IMTP) trials, with all participants' data used for correlational analysis. After testing, females and males were divided into 20 strength-matched pairs, based on their relative peak force (peak force ∙ body mass). There were no meaningful differences between sexes for relative force at 150 ms (g = 0.007 [95% CI -0.627, 0.648]), 200 ms (g = -0.059 [95% CI -0.695, 0.588]) and 250 ms (g = -0.156 [95% CI -0.778, 0.473]). Similarly, when expressed as a percentage of peak force there were no meaningful differences in force at 150 ms (g = -0.015 [95.0%CI -0.650, 0.680]), 200 ms (g = -0.099 [95.0%CI -0.714, 0.559]) or 250 ms (g = -0.272 [95.0%CI -0.856, 0.328]) between strength-matched females and males. Based on the correlations, there were very large to nearly perfect relationships (r = 0.77-0.94, p <0.001) between peak force and rapid force production, with peak force explaining 59%, 77% and 89% of the variance in force at 150-, 200- and 250 ms, respectively. When comparing females and males, relative strength (based on body weight or a percentage of peak force) should be considered, and practitioners should be aware of the role of peak force in rapid force production.