Should women be provided with unique guidance and support in the field of sport and exercise science compared to men? The simple answer is that currently, we lack sufficient knowledge on this matter. However, we speculate that due to the numerous differences in anatomy, physiology, and psychology between men and women, it may be necessary to offer different guidance based on sex.
Hormonal effects on studies involving female athletes
One of the major discrepancies between men and women lies in reproductive physiology and endocrinology. After puberty, men typically have relatively stable levels of sex hormones, whereas adult women experience the following: - Fluctuations in ovarian hormones throughout the menstrual cycle - Regular consumption of synthetic steroid hormones through hormonal contraceptives - Encounters with abnormally high levels of estrogen and progesterone during pregnancy, followed by a rapid decline in ovarian hormone concentrations during menopause.These dynamic changes in reproductive hormone profiles serve as the foundation for studies investigating sex differences, as well as the effects of menstrual cycle phases, hormonal contraceptive use, pregnancy, and menopause on various aspects of nutrition, training, performance, and health.
The need for further research
Regrettably, almost all studies conducted in the field of sport and exercise science involving female participants conclude with the phrase, "...more research is needed." However, a more accurate statement would be "...more high-quality research is needed." Alongside the current scarcity of data specific to females, there is a lack of high-quality data primarily attributed to two factors:
- unclear criteria for selecting participants
- inadequate experimental designs.
Who is being studied?
This issue pertains to the vague definition, selection, and confirmation of the sampled population. For instance, in the past, researchers have made assumptions about a participant's eumenorrheic status solely based on the presence of menstruation. In reality, menstruation can occur in anovulatory cycles (cycles without ovulation) and luteal phase deficient cycles (cycles with reduced progesterone levels in the mid-luteal phase), neither of which should be considered eumenorrheic cycles.Moreover, there has been an excessive focus on the menstrual cycle in studies related to sport and exercise science, whereas it only represents a portion, not the majority, of women. Moving forward, we need to consider:
- Participants in the pubertal stage
- Users of hormonal contraceptives (beyond just oral contraceptive pills)
- Pregnant women - Women with menstrual irregularities (e.g., amenorrhea, oligomenorrhea)
- Menopausal women
- Users of hormone replacement therapy
Each of these groups of women possesses distinct ovarian hormone profiles (varying levels of estrogen and progesterone). It is evident that "women" cannot be treated as a homogeneous group. Therefore, we require clear and universally applicable definitions for each ovarian-based hormonal profile associated with women throughout their lifespan. By establishing these definitions beforehand and confirming them retrospectively, we can ensure that the sampled population accurately represents the intended "type" or "category" of woman.
Regarding experimental design, studies involving female participants need to take the following factors into account:
- The duration (e.g., tracking menstrual cycle characteristics for ≥ 2 months before the study begins) and procedures (e.g., blood sample analysis to determine estrogen and progesterone levels and identify/confirm a specific phase of the menstrual cycle) required
- The number of times a participant needs to be tested/assessed (e.g., two, three, four... phases of the menstrual cycle) and the timing of those sessions (e.g., during menstruation, in the 24 hours preceding or following confirmation of ovulation, + 7 days after confirming ovulation) to accurately represent their ovarian hormonal profile
- The inter and intra-individual variability in ovarian hormone profiles (e.g., the length of eumenorrheic cycles can range from 21 to 35 days) and how to address this variability (e.g., using only one brand/type of oral contraceptive pill to minimize variations in endogenous estrogen concentrations).
Consequently, the experimental design of studies involving female participants needs to adapt based on the ovarian hormonal status of the participants (e.g., considering menstrual cycle phase, type of hormonal contraceptive used, stage of menopause).
By carefully and consistently considering the characteristics of the sample and adapting the research design to incorporate female-specific criteria, sport and exercise scientists will be able to generate valuable data specific to females, bridge the data gap between sexes, and support female athletes in realizing their full potential in sports regardless of their reproductive status.
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- Elliott-Sale KJ, Minahan CL, de Jonge XAKJ, Ackerman KE, Sipilä S, Constantini NW, Lebrun CM, Hackney AC. Methodological Considerations for Studies in Sport and Exercise Science with Women as Participants: A Working Guide for Standards of Practice for Research on Women. Sports Med. 2021 Mar 16. doi: 10.1007/s40279-021-01435-8.