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INFLUENCE OF MENSTRUAL CYCLE PHASE AND HORMONAL CONTRACEPTIVE USE ON RESISTANCE EXERCISE PERFORMANCE AND FATIGUE

Abstract

Little research is available on potential implications of endogenous vs exogenous female steroid hormones on resistance exercise performance. Examining fatigue outcomes while considering these female specific factors could help maximize training performance. PURPOSE: To examine performance fatigability and muscular endurance during deadlift repetitions performed to failure at a moderate intensity between oral contraceptive pill (OCP) users and naturally menstruating (NM) females across two cycle phases: a low hormone phase (P1) and a high hormone phase (P2). METHODS: 9 monophasic OCP users (22.4 ± 5.0 yrs) and 11 NM females (20.7 ± 1.0 yrs) performed a one-repetition maximum (1RM) for the deadlift and repetitions to failure at 40% 1RM during phase 1 (P1 OCP: placebo week, NM: menstruation) and phase 2 (P2; OCP: active pill week 1-2, NM: ovulation) on separate days. Females completed pre- and post- exercise maximal voluntary contractions (MVC) with a mid-thigh pull dynamometer to determine performance fatigability (%change pre- to post-MVC). Separate 2 (group: OCP, NM) x 2 (phase: 1, 2) repeated measures ANOVAs were used to determine differences in repetitions completed and performance fatigability, and a< 0.05. RESULTS: There was no significant interaction (p = 0.385) or main effect of group (p = 0.969) or phase (p = 0.973) for repetitions completed (P1 OCP: 52 ± 16 reps, NM: 55 ± 23 reps; P2 OCP: 54 ± 13 reps, NM: 52 ± 18 reps). There was a significant interaction for performance fatigability (p = 0.012, pη2 = 0.300). Follow-up independent samples t-tests indicated OCP experienced greater fatigability than NM during P2 (%change OCP: 47.9 ± 19.4%, NM: 30.1 ± 10.6%, p = 0.030), but not P1 (%change OCP: 37.3 ± 23.9%, NM: 38.0 ± 9.8%, p = 0.934). Follow-up paired samples t-tests showed no difference between P1 and P2 for OCP (p=0.103) or NM (p=0.063). CONCLUSION: Total repetitions completed in a single session were not impaired, but the ability to generate force following exhaustive exercise was diminished during the high hormone phase of OCP users when compared to NM females. NM females did not experience changes due to phase. Thus, coaches and practitioners should not program resistance training around the menstrual cycle or OCP phase but should be mindful of the recovery of force-generating capacity in OCP users during the active pill phase.

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