Exploring the Impact of Ovarian Hormones on Cortical Drive and Quadriceps Performance in Uninjured Female Athletes.

BACKGROUND

Ovarian hormones fluctuate across the menstrual cycle (MC) and differ between oral contraceptive (OC) users and naturally menstruating (NM) individuals. Hormones may affect cortical drive to peripheral muscles through excitatory effects of estradiol and inhibitory effects of progesterone on the central nervous system. The impact of hormones on cortical drive is poorly understood. This study aimed to (1) determine the effects of MC phase and OC use on cortical drive and quadriceps performance and (2) determine the relationship between ovarian hormones and these outcomes. We hypothesized that cortical drive will differ between MC phases in NM individuals but not in OC users. Cortical drive will be positively associated with circulating estradiol.

METHODS

Fourteen NM individuals and 11 OC users completed two time points (high hormone: NM mid-luteal, OC active pill and low hormone: NM early follicular, OC placebo). Hormone concentrations were quantified using enzyme-linked immunosorbent assays. Quadriceps performance (isometric peak torque [PTISOM] and rate of torque development) was measured using an isokinetic dynamometer. Corticospinal excitability and intracortical excitability (short-interval intracortical inhibition [SICI] and intracortical facilitation) were assessed using transcranial magnetic stimulation. Linear mixed-effect models were used to examine hormone status, phase, and interaction effects. Linear regression determined associations between hormones, cortical drive, and strength.

RESULTS

There were no significant main effects or interactions for any cortical drive measure. There was a phase by hormone status interaction on the rate of torque development from 0 to 100 ms (RTD100), with a greater RTD100 at the high hormone phase than at the low hormone phase in the NM group but no difference between time points in the OC group. There was a main effect of phase on PTISOM, with a greater PTISOM at the low hormone phase regardless of hormone status. SICI was negatively associated with estradiol. RTD100 was positively associated with progesterone and moderated by hormone status.

CONCLUSIONS

MC phase did not impact cortical drive but did impact quadriceps performance. There were between-phase differences in speed of contraction among NM individuals but not among OC users. A higher progesterone level was associated with faster speed of contraction, especially among NM participants.

KEY CONCEPTS: (1)Corticospinal and intracortical excitability did not differ by menstrual cycle (MC) phase or oral contraceptive (OC) use.(2)Quadriceps rate of torque development was associated with progesterone concentration and varied across the MC, suggesting hormone expression influenced the rate of torque development (RTD) (speed of contraction).(3)The influence of endogenous ovarian hormones on RTD (speed of contraction) differed between OC users and naturally menstruating individuals.

LEVEL OF EVIDENCE: II.