Sex Differences in Physical Fitness in Recreational CrossFit® Participants

CrossFit® requires the integration of strength, power, and cardiorespiratory fitness, although sex-related differences across these physical fitness components remain poorly characterized in recreational participants. This study compared anthropometric characteristics, body composition, neuromuscular performance, maximal strength, and cardiorespiratory fitness between male and female recreational CrossFit® participants. Twenty-three participants were included, comprising 11 males (29.5 ± 5.6 years; 79.4 ± 9.0 kg; 174.9 ± 5.3 cm) and 12 females (28.8 ± 5.2 years; 64.7 ± 6.8 kg; 163.3 ± 6.2 cm; mean ± SD). CrossFit® training experience was 20.7 ± 9.5 months in males and 13.3 ± 6.9 months in females. Participants completed a countermovement jump, drop jump, horizontal jump, one-repetition maximum back squat, deadlift, and thruster assessments, followed by the Yo-Yo Intermittent Recovery Test Level 1. Differences between sexes were examined using Welch’s independent-samples t-test, with Cohen’s d used to quantify effect sizes. Males had greater countermovement jump power (1369 ± 481 vs. 732 ± 119 W; Cohen’s d = 1.85), drop jump power (2056 ± 690 vs. 1040 ± 254 W; d = 1.99), horizontal jump performance (213 ± 30 vs. 161 ± 28 cm; d = 1.78), back squat (133 ± 20 vs. 78 ± 22 kg; d = 2.61), deadlift (164 ± 32 vs. 97 ± 36 kg; d = 1.99), and thruster strength (72.5 ± 21.4 vs. 37.3 ± 19.0 kg; d = 1.74; all p ≤ 0.006). Differences remained large when jump power and maximal strength were expressed relative to body mass (d = 1.27–1.77) and were further attenuated when normalized to estimated muscle mass (d = 0.72–0.98). The exploratory strength ratios did not reach statistical significance. However, the study had limited sensitivity to detect effects below Cohen’s d = 1.23. Males also covered ~40% greater distance in the Yo-Yo Intermittent Recovery Test Level 1 (p = 0.011; d = 1.18), corresponding to ~6% higher estimated maximal oxygen uptake. Sex differences were greatest in strength and neuromuscular performance, and smaller in cardiorespiratory fitness, highlighting the value of assessing both absolute and relative fitness measures in recreational CrossFit® participants.