Minimal influence of the menstrual cycle or hormonal contraceptives on performance in female rugby league athletes

Abstract

We examined performance across one menstrual cycle (MC) and 3 weeks of hormonal contraceptives (HC) use to identify whether known fluctuations in estrogen and progesterone/progestin are associated with functional performance changes. National Rugby League Indigenous Women's Academy athletes [n = 11 naturally menstruating (NM), n = 13 using HC] completed performance tests [countermovement jump (CMJ), squat jump (SJ), isometric mid-thigh pull, 20 m sprint, power pass and Stroop test] during three phases of a MC or three weeks of HC usage, confirmed through ovulation tests alongside serum estrogen and progesterone concentrations. MC phase or HC use did not influence jump height, peak force, sprint time, distance thrown or Stroop effect. However, there were small variations in kinetic and kinematic CMJ/SJ outputs. NM athletes produced greater mean concentric power in MC phase four than one [+0.41 W·kg^-1 (+16.8%), p = 0.021] during the CMJ, alongside greater impulse at 50 ms at phase one than four [+1.7 N·s (+4.7%), p = 0.031] during the SJ, without differences between tests for HC users. Among NM athletes, estradiol negatively correlated with mean velocity and power (r = -0.44 to -0.50, p < 0.047), progesterone positively correlated with contraction time (r = 0.45, p = 0.045), and both negatively correlated with the rate of force development and impulse (r = -0.45 to -0.64, p < 0.043) during the SJ. During the CMJ, estradiol positively correlated to 200 ms impulse (r = 0.45, p = 0.049) and progesterone to mean power (r = 0.51, p = 0.021). Evidence of changes in testing performance across a MC, or during active HC use, is insufficient to justify "phase-based testing"; however, kinetic or kinematic outputs may be altered in NM athletes.

Keywords: estrogen; female; progesterone; sex hormones; strength; women.

FIGURE 1

Study overview. Performance testing occurred at either (A) phases one [low estrogen/progesterone concentration (day 1.8 ± 0.4)], two [high estrogen and low progesterone (day 11.4 ± 1.4)] and four [moderate estrogen and progesterone (day 20.8 ± 1.6)] for athletesNM. The days reported refer to the cycle day on which the test was conducted; (B) three equally spaced timepoints for athletesHC utilizing the implant or hormonal injection or, three equally spaced timepoints avoiding the withdrawal bleed for athletesHC using the oral contraceptive pills. It should be noted that the concentration of exogenous progestin following the implant and injection gradually declines with time (Huber, 1998), and hence the exact hormonal profile is dependent on the date of the implant or injection. Time points are displayed according to an idealized 28‐day cycle. (C) Performance testing schedule. Figure created with BioRender.com. HC, hormonal contraceptives; IMTP, isometric mid‐thigh pull; NM, naturally menstruating; OCP, oral contraceptive pills.

FIGURE 2

Serum estradiol concentration across the three tests in (A) naturally menstruating athletes and (B) athletes using hormonal contraception (n = 1 outlier removed during test three). Serum progesterone concentration across the tests in (C) naturally menstruating athletes (n = 1 outlier removed during phase four) and (D) athletes using hormonal contraception. Calculated free testosterone across the tests in (E) naturally menstruating athletes and (F) athletes using hormonal contraception. Total testosterone across the tests in (G) naturally menstruating athletes and (H) athletes using hormonal contraception. Black lines denote mean values. *denotes significance p < 0.05, **denotes significance p < 0.001.

FIGURE 3

Performance outcomes at each test, alongside relative mean power during the countermovement jump and impulse at 50 ms during the squat jump, between naturally menstruating athletes (athletesNM) and athletes using hormonal contraception (athletesHC). *denotes significance p < 0.05.