Influence of the Menstrual Cycle on Performance in CrossFit®

The purpose of this study was to compare the fast maximal dynamic strength, maximal dynamic strength, and muscular endurance changes between the follicular phase (FP) and luteal phase (LP) in the menstrual cycle (MC). Fourteen healthy resistance-trained CrossFit® athletes and eumenorrheic women without oral contraception participated in this study (age: 29.64 ± 3.95 years; height: 1.62 ± 0.04 m and mass: 60.43 ± 6.56 kg). A double cross-sectional and descriptive study was developed to evaluate strength, power, and muscular endurance performance in the FP (days 5 to 7) and LP (days 20 to 23). In each assessment, the subjects performed three countermovement jumps (CMJs) for assessing fast maximal dynamic strength using My Jump 2, one-repetition maximum (1-RM) on deep squat for maximal dynamic strength, and the Karen® protocol for muscular endurance. The data were analyzed using a paired sample t-test to determine whether there were any significant differences between FP and LP for all the assessments and the significance was set at p ≤ 0.05. Results revealed no significant differences between the FP and LP in performance: (a) fast maximal dynamic strength (FP: 0.27 ± 0.04 m; LP: 0.29 ± 0.04 m; t = 0.98; p = 0.34; ES = 0.26); (b) maximal dynamic strength (FP: 88.14 ± 12.60 kg; LP: 87.07 ± 12.51 kg; t = 0.90; p = 0.38; ES = 0.24); and (c) muscular endurance (FP: 459.43 ± 92.71 s; LP: 456.93 ± 110.68 s; t = 0.27; p = 0.78; ES = 0.07). CrossFit® performance is not altered during the MC in CrossFit® trained athletes. However, monitoring the MC and its symptoms could be used to adapt the training prescription to the needs and preferences of the athletes.