Methodological Considerations for Studies in Sport and Exercise Science with Women as Participants: A Working Guide for Standards of Practice for Research on Women

Abstract

Until recently, there has been less demand for and interest in female-specific sport and exercise science data. As a result, the vast majority of high-quality sport and exercise science data have been derived from studies with men as participants, which reduces the application of these data due to the known physiological differences between the sexes, specifically with regard to reproductive endocrinology. Furthermore, a shortage of specialist knowledge on female physiology in the sport science community, coupled with a reluctance to effectively adapt experimental designs to incorporate female-specific considerations, such as the menstrual cycle, hormonal contraceptive use, pregnancy and the menopause, has slowed the pursuit of knowledge in this field of research. In addition, a lack of agreement on the terminology and methodological approaches (i.e., gold-standard techniques) used within this research area has further hindered the ability of researchers to adequately develop evidenced-based guidelines for female exercisers. The purpose of this paper was to highlight the specific considerations needed when employing women (i.e., from athletes to non-athletes) as participants in sport and exercise science-based research. These considerations relate to participant selection criteria and adaptations for experimental design and address the diversity and complexities associated with female reproductive endocrinology across the lifespan. This statement intends to promote an increase in the inclusion of women as participants in studies related to sport and exercise science and an enhanced execution of these studies resulting in more high-quality female-specific data.

Fig. 1

Indicative oestrogen and progesterone profiles across the lifespan from childhood to senescence: a oestrogen (pmol∙L⁻¹). With regards to oestrogen, the menstrual cycle has 20 times more oestrogen than pre-puberty and pregnancy 35 times more oestrogen than the menstrual cycle; b progesterone (nmol∙L⁻¹). The menstrual cycle has 35 times more progesterone than pre-puberty and pregnancy almost 7 times more progesterone than during the menstrual cycle. Oral contraceptives users and post-menopausal women have similar levels of endogenous oestrogen and progesterone. Hypothalamic-pituitary forms of amenorrhea (not depicted here) do not show any evidence of oestrogen production based on urinary measurements [1]. In women, “oestrogen” includes the oestrone, oestradiol, oestriol hormones

Fig. 2

Oestrogen reference ranges from three different sources^1,2,3 for the follicular (F), ovulatory (O) and luteal (L) phases of the menstrual cycle. All sources are clinical reference ranges from different National Health Service Trusts in the UK and are based on the manufacturers' laboratory reference ranges. This figure illustrates the differences in the reference ranges for each of the three prevailing oestrogen phases of the eumenorrheic menstrual cycle and suggests that additional context is required (e.g., blood sample taken on day two of bleeding, thus allowing the comparison with the follicular range; blood sample taken 12 h after ovulation was denoted by a positive urinary luteinising hormone test kit, thus allowing comparison with the ovulatory range; blood sample taken seven days after ovulation was denoted by a positive urinary luteinising hormone test kit, thus allowing comparison with the luteal range values)

Fig. 3

Progesterone reference ranges from three different sources^1,2,3 for the follicular (F) and luteal (L) phases of the menstrual cycle. All sources are clinical reference ranges from different National Health Service Trusts in the UK and are based on the manufacturers' laboratory reference ranges. This figure illustrates the differences in the reference ranges for each of the two prevailing progesterone phases of the eumenorrheic menstrual cycle and suggests that additional context is required (e.g., blood sample taken on day two of bleeding, thus allowing the comparison with the follicular range; blood sample taken seven days after ovulation was denoted by a positive urinary luteinising hormone test kit, thus allowing comparison with the luteal range values)

Fig. 4

Visual overlay of the hormonal changes across an idealised 28-day menstrual cycle indicating when each phase begins and ends as described in Table 3. The solid gold line represents oestrogen the short dash purple line represents luteinising hormone and the long dash green line represents progesterone. The black dots represent the mean concentration of oestrogen during each phase and the black diamonds represent the mean concentration of progesterone in each phase