Myths and Methodologies: Reducing scientific design ambiguity in studies comparing sexes and/or menstrual cycle phases
Key Findings (as stated in the abstract)
Female athletes remain significantly under-represented in sport and exercise science research; historical exclusion and biomedical disinterest have made sex-difference research harder.
The biphasic rise and fall of oestrogen and progesterone across the menstrual cycle significantly influence physiological responses that contribute to exercise capacity and adaptation in women.
Oral contraceptives add a further layer: varying concentrations of exogenous oestrogen and progestin may moderate adaptation to exercise differently from endogenous ovarian hormones.
Much applied research on women is limited by designs that do not define reproductive status.
The review lays out endogenous and exogenous hormone profiles across a standard 28-32 day cycle so that studies can define phase and contraceptive status properly.
Practical Application
Sims & Heather's 2018 review is a methodology paper: it argues that studies comparing sexes or cycle phases are ambiguous unless reproductive status (natural cycle phase or contraceptive type) is defined, because oestrogen and progesterone shift physiology across the 28-32 day cycle. Use it to judge study quality, not as a source of training or nutrition targets.
Inference, not tested: because the hormone profiles differ between a natural cycle and hormonal contraception, an athlete's own pattern across her cycle or pill pack is the relevant baseline — compare like with like when tracking performance.
Not from this paper: any sex-specific fuelling, protein or iron numbers belong to their own entries — protein for masters athletes in REF-348, iron in REF-340 and SYNTH-06, energy availability in REF-341.
Limitations
Narrative review, not systematic; no quantitative synthesis
The abstract makes no claim about substrate use, thermoregulation, protein needs, sodium or under-fuelling — those topics are outside what this entry can cite
Individual variation across cycles is large; the paper argues for better design, not for specific phase-based prescriptions
How this entry was checked and changed
Why this level
regraded 2026-09-27 from B+: narrative review without systematic method
Content correction 2026-09-27
"Females show higher fat oxidation", "luteal core temperature +0.3-0.5°C", "female athletes routinely under-fuel", "protein 1.6-2.2 g/kg/day", "sodium losses", "ferritin ≥35 ng/mL, re-test every 3-4 months" -> none of these appear in the abstract, which is a methodology review about defining reproductive status; removed. Protein and iron pointers moved to a "Not from this paper" line.
Practical bullets on fuelling, heat-session scheduling by phase, protein and iron targets -> removed; the paper offers no such prescriptions.
Sport "swimming" -> general. Level B+ -> C+ (narrative review).