Table 2.

Summary table of the considerations related to experimental design for women’s studies from puberty to post-menopause

Consideration	Rationale (intended to…)	Pros (could…)	Cons (could…)
Take into account the changes in androstenedione prior to the onset of puberty (e.g., the initial increase in androstenedione has been noted 18 to 12 months prior to the onset of puberty) [60]	Increase breadth of data on reproductive ageing by considering the peri-pubertal period	Increase understanding of the peri-pubertal changes in physiological functioning and athletic performance	Increase timescale of the study in order to identify and group participants along these spectrums
Take into account the changes in oestrogen prior to the onset of puberty (e.g., the initial increase in oestrogen has been noted 12 and 6 months prior to the onset of puberty) [60]
Take into account the time scale of establishing a eumenorrheic cycle: menarche follows an anovulatory cycle; menstrual cycles during the 1st year after menarche are typically irregular and anovulatory, ranging in duration from 21 to 45 days; by 3 years post-menarche, > 90% of girls have ≥ 10 menstrual cycles per year with an average menstrual interval of 36.5 days; cycles can remain irregular until the 5th year post-menarche [61]	Reduce assumption that once menarche has been initiated all girls have fully eumenorrheic cycles	Reduce between participant variability in hormone status
Define menstrual cycle phases based on hormonal profiles (see Table 3), verified by blood analysis with inter and intra-assay variability reported or other robust biochemical methods [62]	Increase reliability of studies Increase validity of findings	Reduce likelihood of grouping non-homogenous hormonal profiles Reduce inconsistency in phase definitions between studies	Increase timescale of the study in order to recruit participants who are willing to undertake blood sampling Increase cost of the study
Track and establish menstrual cycle characteristics for ≥ 2 months prior to testing. Tracking can be achieved by denoting the first and the last day of menstruation on a calendar for each cycle. Corroboration can be achieved by confirmation of ovulation and hormone concentrations		Reduce within participant variation in menstrual cycle characteristics Reduce likelihood of including participants with menstrual irregularities in eumenorrheic studies Increase ability to accurately predict testing timepoints (i.e., phases)	Increase timescale of the study due to the long lead-in time Increase burden on participants to track their cycles before the experimental aspect of the study
Outcome measures should be repeated in a second cycle		Reduce variability of the data	Increase timescale of the study due to the repeated measures Increase burden on participants to repeat all of the testing sessions
Use urinary ovulation kits to establish the mid-cycle surge in LH; visual confirmation should be provided to the researcher [58, 63, 64]		Reduce risk of including anovulatory women in eumenorrheic studies Reduce chance of a false positive result by the participant from an at-home interpretation	Increase chance of missing a positive ovulation result in participants who do not comply or adhere to conducting the test at the same time of day Increase likelihood of overlooking LPD as this method does not exclude LPD cycles
Apply a posteriori exclusion of data from testing timepoints which do not comply with the theoretical (see Fig. 2 and Fig. 3) or stipulated (see Table 3) differences in reproductive hormone concentrations in menstrual cycle studies	Ensure that the intended reproductive profiles were assessed	Reduce likelihood of grouping non-homogenous hormonal profiles	Increase number of participants who need to be excluded (retrospectively) as a result of not fitting the inclusion criteria
Stipulate and take into account OCP-taking (i.e., active OCP) days and OCP-free (i.e., inactive/placebo OCP) days: (i) The endogenous concentration of oestrogen and progesterone rises during the OCP free/inactive/placebo days [65, 66] (ii) The concentration of exogenous hormones increases during active OCP intake: for example, for a combined monophasic OCP ethinyl estradiol (a type of exogenous oestrogen) increases twofold from day 1 of active OCP to day 21 [66, 67] and progestin increases threefold from day 1 of active OCP to day 8–11 and then maintains that level [67, 68]	Increase homogeneity of hormonal profiles	Reduce between participant variability in hormone status	Increase timescale of the study if several conditions need to be assessed
Take into account the rising concentrations of oestrogen and progesterone throughout each trimester of pregnancy			Increase timescale of the study in order to identify and group participants along this spectrum
Take into account the large variation in hormonal profiles associated with the peri-menopause, menopause and post-menopause, thus treating these as separate categories of women based on the criteria outlined in Table 1

Considerations without a reference have been developed by the authors for this paper. OCP oral contraceptive pill, LPD luteal phase deficiency, LH luteinising hormone