Inconsistencies in the perceived impact of the menstrual cycle on sport performance and in the prevalence of menstrual cycle symptoms: A scoping review of the literature.

OBJECTIVES: This scoping review aimed to summarize the findings of studies regarding the perceived impact of the menstrual cycle on athletic performance, as well as the prevalence of negative menstrual cycle symptoms. DESIGN: Scoping review. METHODS: Three databases were searched and the Preferred Reporting Items for Systematic reviews and Meta Analyses extension for Scoping Reviews (PRISMA-ScR) was used as guidance. RESULTS: A total of 39 studies were included in the final analysis. Between 2.8 and 100 % of athletes reported their performance being negatively impacted by their menstrual cycle, and the main reason was the occurrence of menstrual cycle symptoms. Additionally, a large variability in the prevalence of menstrual cycle symptoms was reported in the different studies mainly due to methodological differences and recall biases. CONCLUSIONS: Similarly, as to what has been reported in reviews summarizing performance outcomes during different menstrual cycle phases, this review highlights the high degree of variability between how athletes perceive to be impacted by their menstrual/hormonal contraceptive cycle. REGISTRATION: The protocol of this scoping review was registered at the Open Science Framework on 14 September 2023 (osf.io/efu9x).

Moving from ethnic exclusions to cultural safety: how is athlete ethnicity discussed in research on menstrual health in sports? A scoping review.

OBJECTIVE: This study aims to investigate how athlete ethnicity is discussed in the inclusion and exclusion criteria, methodology, findings, and conclusions of research focused on menstrual health in sports science and medicine. DESIGN: A scoping review of sports-based research conducted on athletes related to (1) menstrual health and ethnicity, (2) how researchers include/exclude participants based on ethnicity and (3) how ethnicity is discussed. DATA SOURCES: Electronic search of PubMed and ProQuest. ELIGIBILITY CRITERIA: Articles were included if they met the following criteria: (1) published before September 2023, (2) published in peer-reviewed journals, (3) participants were women athletes, (4) published in English and (5) relating to menstrual health. Articles were assessed as good, fair or poor quality using the Inclusion of Participant Ethnicity Quality Assessment Criteria. RESULTS: From the 1089 studies available from the initial database search, 55 studies considered ethnicity. Nine studies met the inclusion criteria and were assessed as either good (22%), fair (44%) or poor (33%) in quality in their consideration of athlete ethnicity. 81% of research articles on menstrual health in sports do not consider athlete ethnicity, and when ethnicity is discussed, it rarely meets the criteria for cultural safety in the research process. Most studies did not factor ethnicity into the analysis and lacked cultural considerations in the research design and interventions. CONCLUSION: More careful inclusion of ethnicity in sports menstrual health-related research and recognition of social and cultural influences on health and research outcomes for indigenous and other ethnic minority groups is needed. Such research is required to support coaches, medical personnel and support staff in designing culturally safe environments for sportswomen from diverse cultural and ethnic backgrounds.

Injury Incidence, Severity, and Type Across the Menstrual Cycle in Female Footballers: A Prospective Three Season Cohort Study.

PURPOSE: The aim of the study was to assess the influence of menstrual cycle phase on injury incidence, severity, and type in elite female professional footballers over three seasons. METHODS: Time-loss injuries and menstrual cycle data were prospectively recorded for 26 elite female football players across three seasons. The menstrual cycle was categorized into four phases using a standardized model: menstruation (phase 1; P1), remainder of follicular phase (phase 2; P2), early luteal (phase 3; P3), and premenstrual phase (phase 4; P4). Injury incidence rates (IIR) and ratios (IIRR) were calculated for overall injuries, injury severity, type, contact vs noncontact, and game/training. RESULTS: A total of 593 cycles across 13,390 d were tracked during the study, and 74 injuries from 26 players were eligible for analysis. When comparing IIR between phases (reference: P1), overall injury rates were highest in P4 (IIRR, 2.30 (95% confidence interval, 0.99-5.34; P = 0.05)). When examining rates by injury severity and type, IIR values were also highest in P4 for ≤7 d' time-loss (4.40 (0.93-20.76; P = 0.06)), muscle-specific (6.07 (1.34-27.43; P = 0.02)), and noncontact (3.05 (1.10-8.50; P = 0.03)) injuries. Muscle-specific (IIRR P3/P1, 5.07 (1.16-22.07; P = 0.03)) and ≤7 d' time-loss (4.47 (1.01-19.68; P = 0.05)) injury risk was also significantly higher in P3. Muscle injuries were the most prevalent subtype ( n = 41). No anterior cruciate ligament injuries were recorded across the monitoring period. CONCLUSIONS: Injury risk was significantly elevated during the luteal phase of the menstrual cycle (P3 and P4) among elite female professional footballers. Further research is urgently needed to better understand the influence of the menstrual cycle on injury risk and to develop interventions to mitigate risk.

The Dose-Response in Elite Soccer: Preliminary Insights From Menstrual-Cycle Tracking During the FIFA Women's World Cup 2019.

PURPOSE: This preliminary study examined the influence of estimated menstrual-cycle (MC) phase on responses to soccer matches and training sessions in preparation for and during the FIFA (Fédération internationale de football association) Women's World Cup 2019. METHODS: Twenty outfield players representing a national team were tracked over a 45-day period. External (10-Hz global positioning system; total and distance covered at high-metabolic power [≥20 W·kg-1]) and internal load measures (minutes ≥80% heart-rate maximum, sessional ratings of perceived exertion) were collected during all training and matches, with single-item wellness measures (fatigue, soreness, sleep quality, and sleep duration) collected each morning prior to activity. MC phase was estimated individually via an algorithm, informed from pretournament survey responses and ongoing symptom reporting (FitrWoman). Model comparison statistics were used to determine the impact of estimated MC phase in nonhormonal contraceptive users (n = 16). RESULTS: Sessional rating of perceived exertion responses to total distances ≥5 km were higher during the luteal phase (+0.6-1.0 au; P ≤ .0178) versus menstruation (phase 1), but no other observable dose-response trends were observed. Sleep, fatigue, and soreness ratings were not typically associated with MC phase, with the exception of exacerbated fatigue ratings in luteal versus follicular phase 48 hours postmatch (-0.73 au, P = .0275). CONCLUSIONS: Preliminary findings suggest that estimated MC phase may contribute to the understanding of the dose-response to soccer training and matches.

Menopausal symptoms, exercise practices, and advice received in active women: a multi-country survey of strava app users.

The study aimed to identify the prevalence of symptoms, changes in exercise levels, and exercise advice received during the menopausal transition in a large multi-country sample. Using total population sampling, 2.5 percent of female Strava app users (n = 970) from 7 countries completed an online survey between 14 February 2019 and 11 March 2019. The survey discussed menopause status (perimenopausal or postmenopausal), menopausal symptoms, changes to exercise behaviors, and advice received concerning exercise during menopause. Frequencies, chi-square statistics, and linear regressions were used to analyze data. The most commonly reported menopausal symptoms were sexual (18-83 percent) and cognitive/psychological (77-78 percent). 41 percent of women reported no change in exercise behavior since menopause began (46 percent increased and 11 percent decreased behaviors). The majority (88 percent) of women did not receive advice regarding exercise during menopause. Women who received advice were more likely to report an increase in their exercise than those not receiving advice (60 percent vs 46 percent; X2 (df 2, n = 927) = 7.1, p = .03). Exercise behaviors increased the longer it had been since the menopausal onset (X2 (df 8, n = 937) = 77.42, p < .001). The results suggested high menopausal symptom prevalence in active women and a general lack of exercise advice. More women reported higher symptom prevalence and an increase in exercise participation, the longer it had been since menopause onset. Future research should determine whether these increased exercise behaviors are being used as a coping mechanism.

Nutritional practices to manage menstrual cycle related symptoms: a systematic review.

Certain nutritional practices may reduce menstrual-related symptoms, but there is no current consensus on what foods/supplements are sufficiently evidenced to warrant promotion to reduce menstrual symptoms of naturally menstruating individuals. This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Two online databases were searched for published experimental studies that investigated the effects of foods/supplements on menstrual-related symptoms in eumenorrhoeic women. Extracted data and study characteristics were tabulated and grouped on the basis of food/supplement intervention and dosage compared with UK dietary reference values (DRV) and safe upper limits. In total, twenty-eight studies and twenty-one different foods/supplement interventions were included in the review. None of the studies reported a negative effect on symptoms, twenty-three reported a positive effect and five had no effect. Eighteen different ways of measuring menstrual-related symptoms were described across the studies. The results indicate a lack of consistency in studies to confidently provide information to eumenorrheic, naturally menstruating women regarding the use of foods/supplements to reduce menstrual symptoms. Determination of menstrual-related symptoms varied along with dose and duration of food or supplements provided. These data provide some evidence for the use of vitamin D, calcium, zinc and curcumin to reduce menstrual-related symptoms of non-hormonal contraceptive users, on an individual basis; however, further investigation is required prior to implementation with a focus on robust protocols to determine and measure changes in menstrual symptoms, with interventions adhering to DRV and safe upper limits.

Amenorrhea and oligomenorrhea risk related to exercise training volume and intensity: Findings from 3705 participants recruited via the STRAVA™ exercise application.

OBJECTIVES: To investigate associations between self-reported exercise training habits and amenorrhea/oligomenorrhea among physically active women. DESIGN: A cross-sectional survey was completed by 3705 women (median age = 40 years [quartile 1, quartile 3: 30, 45], body mass index = 22.1 kg/m2 [20.5, 24.2]) representing multiple nationalities and sports via the STRAVA™ exercise application. Respondents selected the amount of time they participated in low intensity, moderate intensity, and high intensity exercise training per week. Amenorrhea/oligomenorrhea was defined as self-reporting ≤10 menses in the last year. METHODS: Associations between weekly exercise volume for low intensity training, moderate intensity training, and high intensity training and amenorrhea/oligomenorrhea were modeled with univariate logistic regression models, followed by adjustment for age and body mass index. RESULTS: Amenorrhea/oligomenorrhea prevalence was 16 % (n = 576/3705), with no difference by country of origin or most sport modes. In adjusted models, participating in low intensity training ≥7 h/week or moderate intensity training ≥6 h/week was associated with 1.43 (95 % confidence interval: 1.04-1.96) and 1.46 (1.10-1.95) greater odds of amenorrhea/oligomenorrhea compared to 2 to 3 h/week, respectively. Similarly, high intensity training ≥5 h/week was associated with 1.41 (1.03-1.92) greater odds of amenorrhea/oligomenorrhea compared to 1 to 2 h/week. Participating in low intensity training for ≤30 min/week compared to 2 to 3 h/week was associated with reduced amenorrhea/oligomenorrhea odds (0.65 [0.44-0.94]). CONCLUSIONS: Taken together, these associations suggest greater weekly exercise volume, irrespective of intensity, may increase amenorrhea/oligomenorrhea risk among physically active women.

Fluid balance during physical work in the heat is not modified by the menstrual cycle when fluids are freely available.

We tested the hypothesis that women may be more at risk of becoming dehydrated during physical work in the heat in the early follicular phase (EF), compared with the late follicular (LF) and mid-luteal (ML) phases of the menstrual cycle when allowed free access to drink. Twelve healthy, eumenorrheic, unacclimated women (26 ± 5 yr) completed three trials (EF, LF, and ML phases) involving 4 h of exposure to 33.8 ± 0.8 °C, 54 ± 1% relative humidity. Each hour, participants walked on a treadmill for 30 min at a rate of metabolic heat production of 338 ± 9 W. Participants drank a cool, flavor-preferred non-caloric sport drink ad libitum. Nude body weight was measured pre- and post-exposure, and percent changes in body weight loss were interpreted as an index of changes in total body water. Total fluid intake and urine output were measured and sweat rate was estimated from changes in body mass corrected for fluid intake and urine output. Fluid intake was not different between phases (EF: 1,609 ± 919 mL; LF: 1,902 ± 799 mL; ML: 1,913 ± 671; P = 0.202). Total urine output (P = 0.543) nor sweat rate (P = 0.907) differed between phases. Percent changes in body mass were not different between phases (EF: -0.5 ± 0.9%; LF: -0.3 ± 0.9%; ML: -0.3 ± 0.7%; P = 0.417). This study demonstrates that the normal hormonal fluctuations that occur throughout the menstrual cycle do not alter fluid balance during physical work in the heat.NEW & NOTEWORTHY The effect of the menstrual cycle on fluid balance during physical work in the heat when fluids are freely available is unknown. This study demonstrates that fluid balance is not modified in women across three distinct phases of the menstrual cycle during physical work in the heat These results indicate that when women have free access to cool fluid during physical work in the heat, they respond similarly across all three phases to maintain fluid homeostasis across the menstrual cycle.

How Lifestyle Changes during the COVID-19 Global Pandemic Affected the Pattern and Symptoms of the Menstrual Cycle.

This research investigated the implications that the COVID-19 pandemic had on the menstrual cycle and any contributing factors to these changes. A questionnaire was completed by 559 eumenorrheic participants, capturing detail on menstrual cycle symptoms and characteristics prior to and during the COVID-19 pandemic lockdown period. Over half of all participants reported to have experienced lack of motivation (61.5%), focus (54.7%) and concentration (57.8%). 52.8% of participants reported an increase in cycle length. Specifically, there was an increase in the median cycle length reported of 5 days (minimum 2 days, maximum 32 days), with a median decrease of 3 days (minimum 2 days and maximum 17 days). A lack of focus was significantly associated with a change in menstrual cycle length (p = 0.038) reported to have increased by 61% of participants. Changes to eating patterns of white meat (increase p = 0.035, decrease p = 0.003) and processed meat (increase p = 0.002 and decrease p = 0.001) were significantly associated with a change in menstrual cycle length. It is important that females and practitioners become aware of implications of environmental stressors and the possible long-term effects on fertility. Future research should continue to investigate any long-lasting changes in symptoms, as well as providing education and support for females undergoing any life stressors that may implicate their menstrual cycle and/or symptoms.

Menstrual Cycle: The Importance of Both the Phases and the Transitions Between Phases on Training and Performance.

The authors present opinions based on their applied experiences of working with female athletes in combination with the existing evidence-based literature. Most of the existing menstrual cycle research focuses on a few steady-state time points within the pre-defined menstrual cycle phases, yet this disregards the day-to-day hormonal changes that women have to accommodate to perform optimally and consistently. The traditional research models are inadequate for studying symptoms and symptom management, and ultimately for supporting athletes to perform well throughout the entirety of their cycle. As such, the monitoring of the day-to-day variation, particularly during the transitions between menstrual cycle phases appears to be an important "overlooked" consideration. This is particularly pertinent considering the known intra-individual and inter-individual variation in menstrual cycle characteristics. Anecdotal and research evidence supports the idea that athletes can use non-pharmacological solutions to mitigate negative menstrual cycle symptoms and do not need to "grit their teeth and roll with it". However, further research (including case studies) is needed in this important research area. Such knowledge should be and needs to be widespread amongst practitioners and athletes as they should not have to figure this out alone. As such, researchers and practitioners need to put more work into understanding symptom aetiology, symptom clusters and their relationship with hormonal changes, menstrual cycle phases and transitions, with potential for a profound impact on individual athlete health and well-being. In so doing, those working with female athletes need to continue building on the recent progress made in educating athletes and practitioners; for example, normalising the discussion of and about the menstrual cycle and all of its implications.

Teachers' Perceptions and Experiences of Menstrual Cycle Education and Support in UK Schools.

The purpose of this study was 2-fold, to (1) explore current education provision in UK schools including barriers to menstrual cycle education and (2) assess the perceived support teachers received to deliver menstrual cycle education. Seven hundred eighty-nine teachers (91% female) from all stages of school education in England (48%), Scotland (24%), Wales (22%) and Northern Ireland (6%) completed an online survey. The survey captured information on menstrual education in schools, teacher's knowledge and confidence of the menstrual cycle, support provided to teachers, provision of menstrual products in school and perceived impact of the menstrual cycle on young people in school. Four hundred ninety-eight teachers reported lessons were provided on the menstrual cycle (63%), predominantly delivered within personal, social, health and economic or science subjects, with over half of the lessons focusing on the biology (56%) or provision of menstrual products (40%) rather than lived experiences (14%). Teachers perceived the menstrual cycle affected participation in PE (88%), pupil confidence (88%), school attendance (82%) and attitude and behavior (82%). Overall, 80% of teachers felt receiving training would be beneficial to improve menstrual education. The results highlight education is scientifically focused, with less education on management of symptoms or lived experiences. Teachers also perceive the menstrual cycle to influence multiple aspects of school attendance and personal performance. There is a need to address menstrual education provided in schools across the UK to help empower girls to manage their menstrual cycle, preventing a negative impact on health and school performance.

Modelling menstrual cycle length in athletes using state-space models.

The ability to predict an individual's menstrual cycle length to a high degree of precision could help female athletes to track their period and tailor their training and nutrition correspondingly. Such individualisation is possible and necessary, given the known inter-individual variation in cycle length. To achieve this, a hybrid predictive model was built using data on 16,524 cycles collected from a sample of 2125 women (mean age 34.38 years, range 18.00-47.10, number of menstrual cycles ranging from 4 to 53). A mixed-effect state-space model was fitted to capture the within-subject temporal correlation, incorporating a Bayesian approach for process forecasting to predict the duration (in days) of the next menstrual cycle. The modelling procedure was split into three steps (1) a time trend component using a random walk with an overdispersion parameter, (2) an autocorrelation component using an autoregressive moving-average model, and (3) a linear predictor to account for covariates (e.g. injury, stomach cramps, training intensity). The inclusion of an overdispersion parameter suggested that [Formula: see text] [Formula: see text] of cycles in the sample were overdispersed. The random walk standard deviation for a non-overdispersed cycle is [Formula: see text] [1.00, 1.09] days while under an overdispersed cycle, the menstrual cycle variance increase in 4.78 [4.57, 5.00] days. To assess the performance and prediction accuracy of the model, each woman's last observation was used as test data. The root mean square error (RMSE), concordance correlation coefficient and Pearson correlation coefficient (r) between the observed and predicted values were calculated. The model had an RMSE of 1.6412 days, a precision of 0.7361 and overall accuracy of 0.9871. In conclusion, the hybrid model presented here is a helpful approach for predicting menstrual cycle length, which in turn can be used to support female athlete wellness.

The development and initial validation of the Health and Reproductive Survey (HeRS).

BACKGROUND: Due to the diversity in profiles associated with the female reproductive cycle and their potential physiological and psychological effects, monitoring the reproductive status of exercising females is important from a practical and research perspective. Moreover, as physical activity can influence menstrual function, the effects of physical activity energy expenditure on reproductive function should also be considered. AIM: The aim of this study was to develop and establish initial face and content validity of the Health and Reproductive Survey (HeRS) for physically active females, which is a retrospective assessment of menstrual function from menarche (first menstruation) to menopause (cessation of menstruation). METHODS: Face validity was evaluated qualitatively, and the initial content validity was established through a principal component analysis. The face validity process was completed by 26 females aged 19-67 years and the content validity was established through a survey sent to a convenience sample of 392 females, of which 230 females (57.9% and aged 18-49 years) completed the survey. RESULTS: The revisions made following the face validation improved the understanding, flow, and coherence of the survey. The principal component analysis indicated that, at a minimum, the survey measures these constructs: menstrual cessation and associated moderators, athletic participation and performance levels (as associated with menstruation change and the menstrual cycle), age and menstrual cessation, hormonal contraception ("birth control"), and menarche and associated moderators. CONCLUSION: The Health and Reproductive Survey (HeRS) is a partially validated tool that can be used by researchers to characterize the menstrual status of physically active females relative to their physical activity status.

Hormonal Contraceptive Use in Football Codes in Australia.

The recent launch of the new National elite women's football competitions in Australia has seen a 20-50% increase in grassroots female participation. With the growing participation across grassroots to elite competitions, understanding the health of female athletes should be prioritized. In elite level athletes, hormonal contraceptive (HC) use is common (~50%), however, little is known about the prevalence and reasons for use and disuse of HC in elite female football athletes. As such, the impact of HC use is often not considered when monitoring the health of female footballers. This study involved a subset of data collected as part of a larger questionnaire investigating menstrual cycle function, hormonal contraception use, and the interaction with training load volume and perceived performance in elite female football code athletes. A total of 177 participants completed the questionnaire across three football codes within Australia (rugby league, rugby union/sevens, Australian football). One third (n = 58) of athletes were currently using HC, predominately in the form of an oral contraceptive pill (OC, n = 47). Reasons for use included: to avoid pregnancy (71%); to control/regulate cycle (38%); and to reduce menstrual pain (36%). However, most athletes using an OC (89%) could not identify the type of pill used (e.g., mono-, bi-, or triphasic). The main reason for disuse was due to the negative side effects (n = 23), such as mood swings, weight gain, and depression/anxiety. Comparing HC users and non-users, there were no statistical differences in the number of reported menstrual symptoms, use of medication to relieve menstrual pain, or frequency for needing to adapt training due to their menstrual cycle (p > 0.05). Since most athletes were unaware of the type of OC they used, female football athletes require further education about the different types of HC, and specifically OC, available to them. Similarities in the symptoms experienced, pain management, and training adaptation requirements between groups suggests that HC use may not have the intended outcome for certain athletes. As such, greater awareness of athlete's personal experiences with the menstrual cycle, how HC may influence their experience, and acknowledgment of non-pharmacological methods to help manage menstrual cycle related symptoms are warranted.

COVID-19-Considerations for the Female Athlete.

The SARS CoV-2 virus (COVID-19) caused the whole sporting calendar to be paused. As we embark on the challenge of navigating through the return to play (RTP) process, there is a necessity to consider the needs of all athletes. This commentary specifically considers recommendations and requirements for the female athlete with a physiological emphasis during and following the COVID-19 pandemic, however, it will be relevant for any similar future scenarios that may present. It is important to acknowledge that there remain many unknowns surrounding COVID-19 and the female athlete both in the short- and long-term.

Prevalence and frequency of menstrual cycle symptoms are associated with availability to train and compete: a study of 6812 exercising women recruited using the Strava exercise app.

OBJECTIVES: The menstrual cycle can affect sports participation and exercise performance. There are very few data on specific menstrual cycle symptoms (symptoms during various phases of the cycle, not only during menstruation) experienced by exercising women. We aimed to characterise the most common symptoms, as well as the number and frequency of symptoms, and evaluate whether menstrual cycle symptoms are associated with sporting outcomes. METHODS: 6812 adult women of reproductive age (mean age: 38.3 (8.7) years) who were not using combined hormonal contraception were recruited via the Strava exercise app user database and completed a 39-part survey. Respondents were from seven geographical areas, and the questions were translated and localised to each region (Brazil, n=892; France, n=1355; Germany, n=839; Spain, n=834; UK and Ireland, n=1350; and USA, n=1542). The survey captured exercise behaviours, current menstrual status, presence and frequency of menstrual cycle symptoms, medication use for symptoms, perceived effects of the menstrual cycle on exercise and work behaviours, and history of hormonal contraception use. We propose a novel Menstrual Symptom index (MSi) based on the presence and frequency of 18 commonly reported symptoms (range 0-54, where 54 would correspond to all 18 symptoms each occurring very frequently). RESULTS: The most prevalent menstrual cycle symptoms were mood changes/anxiety (90.6%), tiredness/fatigue (86.2%), stomach cramps (84.2%) and breast pain/tenderness (83.1%). After controlling for body mass index, training volume and age, the MSi was associated with a greater likelihood of missing or changing training (OR=1.09 (CI 1.08 to 1.10); p≤0.05), missing a sporting event/competition (OR=1.07 (CI 1.06 to 1.08); p≤0.05), absenteeism from work/academia (OR=1.08 (CI 1.07 to 1.09); p≤0.05) and use of pain medication (OR=1.09 (CI 1.08 to 1.09); p≤0.05). CONCLUSION: Menstrual cycle symptoms are very common in exercising women, and women report that these symptoms compromise their exercise participation and work capacity. The MSi needs to be formally validated (psychometrics); at present, it provides an easy way to quantify the frequency of menstrual cycle symptoms.

Variations in strength-related measures during the menstrual cycle in eumenorrheic women: A systematic review and meta-analysis.

OBJECTIVES: To systematically review the current body of research that has investigated changes in strength-related variables during different phases of the menstrual cycle in eumenorrheic women. DESIGN: Systematic review and meta-analysis. METHODS: A literature search was conducted in Pubmed, SPORTDiscus and Web of Science using search terms related to the menstrual cycle and strength-related measures. Two reviewers reached consensus that 21 studies met the criteria for inclusion. Methodological rigour was assessed using the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. Random effects meta-analyses were used to compare the early-follicular, ovulatory and mid-luteal phases for maximal voluntary contraction, isokinetic peak torque, and explosive strength. RESULTS: The assessment of study quality showed that a high level of bias exists in specific areas of study design. Non-significant and small or trivial effect sizes (p≥0.26, Hedges g≤0.35) were identified for all strength-related variables in each comparison between phases. 95% confidence intervals for each comparison suggested the uncertainty associated with each estimate extends to a small effect on strength performance with unclear direction (-0.42≤g≤0.48). The heterogeneity for each comparison was also small (p≥0.83, I2=0%). CONCLUSIONS: Strength-related measures appear to be minimally altered (g≤0.35) by the fluctuations in ovarian sex hormones that occur during the menstrual cycle. This finding should be interpreted with caution due to the methodological shortcomings identified by the quality assessment.

Low energy availability surrogates correlate with health and performance consequences of Relative Energy Deficiency in Sport.

Low energy availability (EA) is suspected to be the underlying cause of both the Female Athlete Triad and the more recently defined syndrome, Relative Energy Deficiency in Sport (RED-S). The International Olympic Committee (IOC) defined RED-S as a syndrome of health and performance impairments resulting from an energy deficit. While the importance of adequate EA is generally accepted, few studies have attempted to understand whether low EA is associated with the health and performance consequences posited by the IOC. OBJECTIVE: The purpose of this cross-sectional study was to examine the association of low EA with RED-S health and performance consequences in a large clinical population of female athletes. METHODS: One thousand female athletes (15-30 years) completed an online questionnaire and were classified as having low or adequate EA. The associations between low EA and the health and performance factors listed in the RED-S models were evaluated using chi-squared test and the odds ratios were evaluated using binomial logistic regression (p<0.05). RESULTS: Athletes with low EA were more likely to be classified as having increased risk of menstrual dysfunction, poor bone health, metabolic issues, haematological detriments, psychological disorders, cardiovascular impairment and gastrointestinal dysfunction than those with adequate EA. Performance variables associated with low EA included decreased training response, impaired judgement, decreased coordination, decreased concentration, irritability, depression and decreased endurance performance. CONCLUSION: These findings demonstrate that low EA measured using self-report questionnaires is strongly associated with many health and performance consequences proposed by the RED-S models.