Minimal influence of the menstrual cycle or hormonal contraceptives on performance in female rugby league athletes.

We examined performance across one menstrual cycle (MC) and 3 weeks of hormonal contraceptives (HC) use to identify whether known fluctuations in estrogen and progesterone/progestin are associated with functional performance changes. National Rugby League Indigenous Women's Academy athletes [n = 11 naturally menstruating (NM), n = 13 using HC] completed performance tests [countermovement jump (CMJ), squat jump (SJ), isometric mid-thigh pull, 20 m sprint, power pass and Stroop test] during three phases of a MC or three weeks of HC usage, confirmed through ovulation tests alongside serum estrogen and progesterone concentrations. MC phase or HC use did not influence jump height, peak force, sprint time, distance thrown or Stroop effect. However, there were small variations in kinetic and kinematic CMJ/SJ outputs. NM athletes produced greater mean concentric power in MC phase four than one [+0.41 W·kg-1 (+16.8%), p = 0.021] during the CMJ, alongside greater impulse at 50 ms at phase one than four [+1.7 N·s (+4.7%), p = 0.031] during the SJ, without differences between tests for HC users. Among NM athletes, estradiol negatively correlated with mean velocity and power (r = -0.44 to -0.50, p < 0.047), progesterone positively correlated with contraction time (r = 0.45, p = 0.045), and both negatively correlated with the rate of force development and impulse (r = -0.45 to -0.64, p < 0.043) during the SJ. During the CMJ, estradiol positively correlated to 200 ms impulse (r = 0.45, p = 0.049) and progesterone to mean power (r = 0.51, p = 0.021). Evidence of changes in testing performance across a MC, or during active HC use, is insufficient to justify "phase-based testing"; however, kinetic or kinematic outputs may be altered in NM athletes.

Auditing the representation of hormonal contraceptives in studies assessing exercise performance in women.

Hormonal contraceptive (HC) users have a different ovarian hormonal profile compared to eumenorrheic women. Due to the prevalence of HC use amongst sportswomen, there has been increased research efforts to understand their impact on exercise performance. The aim was to audit this research. Studies identified were assessed for HC type, athlete calibre, performance outcome, study design, and quality of methodological control regarding ovarian hormonal profiles. Sixty-eight different HCs were reported across 61 studies. Monophasic combined oral contraceptive (OCP) pills represented 60% of HCs, followed by other pills [34%, phasic-combined, progestogen-only, and un-specified], phasic and long acting reversible contraceptives [5%, vaginal ring, patch, implant, injection, intrauterine system] and unspecified HCs (1%). Eleven percent of participants using HCs were classified as highly trained or elite/international with no participants being classed as world class. Whilst the number of studies involving HCs has increased two-fold over the past decade, the number of studies ranked as gold standard has not increased (HC; 2003-57%, 2011-55%, 2022-43%. OCP; 2003-14%, 2011-17%, 2022-12%). Future research assessing HCs and exercise performance should adopt high-quality research designs and include a broader range of HCs in highly trained to world-class populations to increase the reach and impact of research in this area.

Myths and Methodologies: Standardisation in Human Physiology Research-Should We Control the Controllables?

The premise of research in human physiology is to explore a multifaceted system whilst identifying one or a few outcomes of interest. Therefore, the control of potentially confounding variables requires careful thought regarding the extent of control and complexity of standardisation. One common factor to control prior to testing is diet, as food and fluid provision may deviate from participants' habitual diets, yet a self-report and replication method can be flawed by under-reporting. Researchers may also need to consider standardisation of physical activity, whether it be through familiarisation trials, wash-out periods, or guidance on levels of physical activity to be achieved before trials. In terms of pharmacological agents, the ethical implications of standardisation require researchers to carefully consider how medications, caffeine consumption and oral contraceptive prescriptions may affect the study. For research in females, it should be considered whether standardisation between- or within-participants in regards to menstrual cycle phase is most relevant. The timing of measurements relative to various other daily events is relevant to all physiological research and so it can be important to standardise when measurements are made. This review summarises the areas of standardisation which we hope will be considered useful to anyone involved in human physiology research, including when and how one can apply standardisation to various contexts.

Myths and Methodologies: Standardisation in human physiology research-should we control the controllables?

The premise of research in human physiology is to explore a multifaceted system whilst identifying one or a few outcomes of interest. Therefore, the control of potentially confounding variables requires careful thought regarding the extent of control and complexity of standardisation. One common factor to control prior to testing is diet, as food and fluid provision may deviate from participants' habitual diets, yet a self-report and replication method can be flawed by under-reporting. Researchers may also need to consider standardisation of physical activity, whether it be through familiarisation trials, wash-out periods, or guidance on levels of physical activity to be achieved before trials. In terms of pharmacological agents, the ethical implications of standardisation require researchers to carefully consider how medications, caffeine consumption and oral contraceptive prescriptions may affect the study. For research in females, it should be considered whether standardisation between- or within-participants in regards to menstrual cycle phase is most relevant. The timing of measurements relative to various other daily events is relevant to all physiological research and so it can be important to standardise when measurements are made. This review summarises the areas of standardisation which we hope will be considered useful to anyone involved in human physiology research, including when and how one can apply standardisation to various contexts.

Effect of Menstrual Cycle Phase and Hormonal Contraceptives on Resting Metabolic Rate and Body Composition.

The cyclical changes in sex hormones across the menstrual cycle (MC) are associated with various biological changes that may alter resting metabolic rate (RMR) and body composition estimates. Hormonal contraceptive (HC) use must also be considered given their impact on endogenous sex hormone concentrations and synchronous exogenous profiles. The purpose of this study was to determine if RMR and dual-energy X-ray absorptiometry body composition estimates change across the MC and differ compared with HC users. This was accomplished during a 5-week training camp involving naturally cycling athletes (n = 11) and HC users (n = 7 subdermal progestin implant, n = 4 combined monophasic oral contraceptive pill, n = 1 injection) from the National Rugby League Indigenous Women's Academy. MC phase was retrospectively confirmed via serum estradiol and progesterone concentrations and a positive ovulation test. HC users had serum estradiol and progesterone concentrations assessed at the time point of testing. Results were analyzed using general linear mixed model. There was no effect of MC phase on absolute RMR (p = .877), relative RMR (p = .957), or dual-energy X-ray absorptiometry body composition estimates (p > .05). There was no effect of HC use on absolute RMR (p = .069), relative RMR (p = .679), or fat mass estimates (p = .766), but HC users had a greater fat-free mass and lean body mass than naturally cycling athletes (p = .028). Our findings suggest that RMR and dual-energy X-ray absorptiometry body composition estimates do not significantly differ due to changes in sex hormones in a group of athletes, and measurements can be compared between MC phases or with HC usage without variations in sex hormones causing additional noise.

Sweat Characteristics and Fluid Balance Responses During Two Heat Training Camps in Elite Female Field Hockey Players.

We examined the sweat characteristics and fluid balance of elite female field hockey players during two heat training camps. Fourteen elite female field hockey players from the Australian national squad participated in two heat training camps held ∼6 months apart, following winter- (Camp 1) and summer-based training (Camp 2). Daily waking body mass (BM) and urine specific gravity (USG) were collected, along with several markers of sweat and fluid balance across two matches per camp. There was a 19% mean reduction in estimated whole-body sweat sodium concentration from Camp 1 (45.8 ± 6.5 mmol/L) to Camp 2 (37.0 ± 5.0 mmol/L; p < .001). Waking urine specific gravity ≥ 1.020 was observed in 31% of samples, with no significant differences in mean urine specific gravity or BM between camps (p > .05), but with substantial interindividual variation. Intramatch sweat rates were high (1.2-1.8 L/hr), with greater BM losses in Camp 1 (p = .030), resulting in fewer players losing ≥2% BM in Camp 2 (0%-8%), as compared with Camp 1 (36%-43%; p = .017). Our field data suggest that elite female field hockey players experience substantial sweat losses during competition in the heat regardless of the season. In agreement with previous findings, we observed substantial interindividual variation in sweat and hydration indices, supporting the use of individualized athlete hydration strategies.

Female Athlete Research Camp: A Unique Model for Conducting Research in High-Performance Female Athletes.

PURPOSE: The purpose of this study is to describe the implementation of a novel research protocol for conducting research with highly trained female athletes, including characterizing menstrual cycle (MC) function, hormonal profiles and symptoms of the participating athletes. METHODS: Twenty-four Australian First Nation female Rugby League athletes completed this study, which involved 11 wk of cycle tracking, followed by attendance at a 5-wk training camp. Throughout the study, athletes completed a daily survey, reporting their MC function and any associated symptoms. During the training camp, athletes reported to the laboratory on three occasions and provided a venous blood sample, which was analyzed for reproductive hormones. For naturally cycling athletes (athleteNC, n = 11), this included phase 1, 2, and 4 of the menstrual cycle, whereas athletes using hormonal contraception (athleteHC; n = 13) were tested at three equally spaced time points in which consistent exogenous hormone provision occurred. RESULTS: In the athleteNC cohort, just one athlete reached criteria for classification as eumenorrheic, with five athletes showing evidence of MC dysfunction. The prevalence of symptoms on any given day was similar between athleteNC (33.7%) and athleteHC (22.9%; P = 0.376); however, more symptoms were reported in athleteNC, suggesting that they were more likely to report multiple symptoms. Regardless of MC function, there was a significant, positive association between bleeding and symptoms ( P < 0.001), where athletes were more likely to report one or more symptoms on bleeding (50.1%) compared with nonbleeding days (22.0%). CONCLUSIONS: We describe an innovative strategy to investigate the effect of MC function and MC phase in a high-performance sport environment, including approaches to address the challenges of undertaking research with female athletes with MC variability and those using exogenous hormonal therapies.

Iron Absorption in Highly Trained Male Runners: Does it Matter When and Where You Eat Your Iron?

PURPOSE: We examined iron absorption and its regulation during two common scenarios experienced by endurance athletes. Our aims were to: (i) compare the effects of preexercise versus postexercise iron intake on iron absorption; and (ii) compare the impact of training at altitude (1800 m) on iron absorption preexercise. METHODS: Male runners (n = 18) completed three exercise trials over a 5-wk period, each preceded by 24 h of standardized low-iron diets. First, athletes completed two 60-min treadmill running trials at 65% V̇O2max at near sea-level (580 m). In a randomized order, preexercise and postexercise test meals labeled with 4 mg of 57Fe or 58Fe were consumed 30 min before or 30 min after exercise. Then, the same exercise trial was performed after living and training at altitude (~1800 m) for 7 d, with the labeled test meal consumed 30 min preexercise. We collected venous blood samples preexercise and postexercise for markers of iron status and regulation, and 14 d later to measure erythrocyte isotope incorporation. RESULTS: No differences in fractional iron absorption were evident when test meals were consumed preexercise (7.3% [4.4, 12.1]) or postexercise (6.2% [3.1, 12.5]) (n = 18; P = 0.058). Iron absorption preexercise was greater at altitude (18.4% [10.6, 32.0]) than at near sea-level (n = 17; P < 0.001) and hepcidin concentrations at altitude were lower at rest and 3 h postexercise compared with near sea level (P < 0.001). CONCLUSIONS: In an acute setting, preexercise and postexercise iron absorption is comparable if consumed within 30 min of exercise. Preexercise iron absorption increases 2.6-fold at altitude compared with near sea-level, likely due to the homeostatic response to provide iron for enhanced erythropoiesis and maintain iron stores.

Low Carbohydrate, High Fat Diet Alters the Oral Microbiome without Negating the Nitrite Response to Beetroot Juice Supplementation.

A low carbohydrate, high fat (LCHF) diet in athletes increases fat oxidation but impairs sports performance, potentially due to impaired exercise economy. Dietary nitrate supplementation can improve exercise economy via an increase in nitric oxide production, which is initiated by the reduction of nitrate to nitrite within the oral cavity. This reaction is dependent on the presence of nitrate-reducing oral bacteria, which can potentially be altered by dietary changes, including a LCHF diet. This study explored the effect of a LCHF diet on the oral microbiome and subsequent changes to plasma nitrite concentration following nitrate supplementation. Following five days of LCHF or high carbohydrate (HCHO) control dietary intervention, highly trained male race walkers consumed 140 mL beetroot juice containing 8.4 mmol nitrate; they then provided (a) blood samples for plasma nitrate and nitrite analysis and (b) saliva samples for 16S rRNA sequencing of the oral microbiome. The LCHF diet (n = 13) reduced oral bacterial diversity and changed the relative abundance of the genera Neisseria (+10%), Fusobacteria (+3%), Prevotella (-9%), and Veillonella (-4%), with no significant changes observed following the HCHO diet (n = 11). Following beetroot juice ingestion, plasma nitrite concentrations were higher for the LCHF diet compared to the HCHO diet (p = 0.04). However, the absence of an interaction with the trial (pre-post) (p = 0.71) suggests that this difference was not due to the dietary intervention. In summary, we found an increase in plasma nitrate and nitrite concentrations in response to nitrate supplementation independent of diet. This suggests the oral microbiome is adaptive to dietary changes and can maintain a nitrate reduction capacity despite a decrease in bacterial diversity following the LCHF diet.

Use of Buffers in Specific Contexts: Highly Trained Female Athletes, Extreme Environments and Combined Buffering Agents-A Narrative Review.

This narrative review evaluated the evidence for buffering agents (sodium bicarbonate, sodium citrate and beta-alanine), with specific consideration of three discrete scenarios: female athletes, extreme environments and combined buffering agents. Studies were screened according to exclusion and inclusion criteria and were analysed on three levels: (1) moderating variables (supplement dose and timing, and exercise test duration and intensity), (2) design factors (e.g., use of crossover or matched group study design, familiarisation trials) and (3) athlete-specific factors (recruitment of highly trained participants, buffering capacity and reported performance improvements). Only 19% of the included studies for the three buffering agents reported a performance benefit, and only 10% recruited highly trained athletes. This low transferability of research findings to athletes' real-world practices may be due to factors including the small number of sodium citrate studies in females (n = 2), no studies controlling for the menstrual cycle (MC) or menstrual status using methods described in recently established frameworks, and the limited number of beta-alanine studies using performance tests replicating real-world performance efforts (n = 3). We recommend further research into buffering agents in highly trained female athletes that control or account for the MC, studies that replicate the demands of athletes' heat and altitude camps, and investigations of highly trained athletes' use of combined buffering agents. In a practical context, we recommend developing evidence-based buffering protocols for individual athletes which feature co-supplementation with other evidence-based products, reduce the likelihood of side-effects, and optimise key moderating factors: supplement dose and timing, and exercise duration and intensity.

Menstrual cycle hormones and oral contraceptives: a multimethod systems physiology-based review of their impact on key aspects of female physiology.

Hormonal changes around ovulation divide the menstrual cycle (MC) into the follicular and luteal phases. In addition, oral contraceptives (OCs) have active (higher hormone) and placebo phases. Although there are some MC-based effects on various physiological outcomes, we found these differences relatively subtle and difficult to attribute to specific hormones, as estrogen and progesterone fluctuate rather than operating in a complete on/off pattern as observed in cellular or preclinical models often used to substantiate human data. A broad review reveals that the differences between the follicular and luteal phases and between OC active and placebo phases are not associated with marked differences in exercise performance and appear unlikely to influence muscular hypertrophy in response to resistance exercise training. A systematic review and meta-analysis of substrate oxidation between MC phases revealed no difference between phases in the relative carbohydrate and fat oxidation at rest and during acute aerobic exercise. Vascular differences between MC phases are also relatively small or nonexistent. Although OCs can vary in composition and androgenicity, we acknowledge that much more work remains to be done in this area; however, based on what little evidence is currently available, we do not find compelling support for the notion that OC use significantly influences exercise performance, substrate oxidation, or hypertrophy. It is important to note that the study of females requires better methodological control in many areas. Previous studies lacking such rigor have contributed to premature or incorrect conclusions regarding the effects of the MC and systemic hormones on outcomes. While we acknowledge that the evidence in certain research areas is limited, the consensus view is that the impact of the MC and OC use on various aspects of physiology is small or nonexistent.

The Impact of a Short-Term Ketogenic Low-Carbohydrate High-Fat Diet on Biomarkers of Intestinal Epithelial Integrity and Gastrointestinal Symptoms.

Endurance exercise can disturb intestinal epithelial integrity, leading to increased systemic indicators of cell injury, hyperpermeability, and pathogenic translocation. However, the interaction between exercise, diet, and gastrointestinal disturbance still warrants exploration. This study examined whether a 6-day dietary intervention influenced perturbations to intestinal epithelial disruption in response to a 25-km race walk. Twenty-eight male race walkers adhered to a high carbohydrate (CHO)/energy diet (65% CHO, energy availability = 40 kcal·kg FFM-1·day-1) for 6 days prior to a Baseline 25-km race walk. Athletes were then split into three subgroups: high CHO/energy diet (n = 10); low-CHO, high-fat diet (LCHF: n = 8; <50 g/day CHO, energy availability = 40 kcal·kg FFM-1·day-1); and low energy availability (n = 10; 65% CHO, energy availability = 15 kcal·kg FFM-1·day-1) for a further 6-day dietary intervention period prior to a second 25-km race walk (Adaptation). During both trials, venous blood was collected pre-, post-, and 1 hr postexercise and analyzed for markers of intestinal epithelial disruption. Intestinal fatty acid-binding protein concentration was significantly higher (twofold increase) in response to exercise during Adaptation compared to Baseline in the LCHF group (p = .001). Similar findings were observed for soluble CD14 (p < .001) and lipopolysaccharide-binding protein (p = .003), where postexercise concentrations were higher (53% and 36%, respectively) during Adaptation than Baseline in LCHF. No differences in high CHO/energy diet or low energy availability were apparent for any blood markers assessed (p > .05). A short-term LCHF diet increased intestinal epithelial cell injury in response to a 25-km race walk. No effect of low energy availability on gastrointestinal injury or symptoms was observed.

Adherence to a Ketogenic Low-Carbohydrate, High-Fat Diet Is Associated With Diminished Training Quality in Elite Racewalkers.

PURPOSE: To examine the effects of a high-carbohydrate diet (HCHO), periodized-carbohydrate (CHO) diet (PCHO), and ketogenic low-CHO high-fat diet (LCHF) on training capacity. METHODS: Elite male racewalkers completed 3 weeks of periodic training while adhering to their dietary intervention. Twenty-nine data sets were collected from 21 athletes. Each week, 6 mandatory training sessions were completed, with additional sessions performed at the athlete's discretion. Mandatory sessions included an interval session (10 × 1-km efforts on a 6-min cycle), tempo session (14 km with a 450-m elevation gain), 2 long walks (25-40 km), and 2 easy walks (8-12 km) where "sleep-low" and "train-low" dietary strategies were employed for PCHO. Racewalking speed, heart rate, rating of perceived exhaustion, and blood metabolites were collected around key sessions. RESULTS: LCHF covered less total distance than HCHO and PCHO (P < .001); however, no differences in training load between groups were evident (P = .285). During the interval sessions, walking speed was slower in LCHF (P = .001), equating to a 2.8% and 5.6% faster speed in HCHO and PCHO, respectively. LCHF was also 3.2% slower in completing the tempo session than HCHO and PCHO (P = .001). Heart rate was higher (P = .002) and lactate concentrations were lower (P < .001) in LCHF compared to other groups, despite slower walking speeds during the interval session. No between-groups differences in rating of perceived exhaustion were evident (P = .077). CONCLUSION: Athletes adhering to an LCHF diet showed impaired training capacity relative to their high-CHO-supported counterparts, completing lower training volumes at slower speeds, with higher heart rates.

Factors Influencing the Hepcidin Response to Exercise: An Individual Participant Data Meta-analysis.

BACKGROUND: Hepcidin, the master iron regulatory hormone, has been shown to peak 3-6 h postexercise, and is likely a major contributor to the prevalence of iron deficiency in athletes. Although multiple studies have investigated the hepcidin response to exercise, small sample sizes preclude the generalizability of current research findings. OBJECTIVE: The aim of this individual participant data meta-analysis was to identify key factors influencing the hepcidin-exercise response. METHODS: Following a systematic review of the literature, a one-stage meta-analysis with mixed-effects linear regression, using a stepwise approach to select the best-fit model, was employed. RESULTS: We show that exercise is associated with a 1.5-2.5-fold increase in hepcidin concentrations, with pre-exercise hepcidin concentration accounting for ~ 44% of the variance in 3 h postexercise hepcidin concentration. Although collectively accounting for only a further ~ 3% of the variance, absolute 3 h postexercise hepcidin concentrations appear higher in males with lower cardiorespiratory fitness and higher pre-exercise ferritin levels. On the other hand, a greater magnitude of change between the pre- and 3 h postexercise hepcidin concentration was largely attributable to exercise duration (~ 44% variance) with a much smaller contribution from VO2max, pre-exercise ferritin, sex, and postexercise interleukin-6 (~ 6% combined). Although females tended to have a lower absolute 3 h postexercise hepcidin concentration [1.4 nmol·L-1, (95% CI [- 2.6, - 0.3]), p = 0.02] and 30% less change (95% CI [-54.4, - 5.1]), p = 0.02) than males, with different explanatory variables being significant between sexes, sample size discrepancies and individual study design biases preclude definitive conclusions. CONCLUSION: Our analysis reveals the complex interplay of characteristics of both athlete and exercise session in the hepcidin response to exercise and highlights the need for further investigation into unaccounted-for mediating factors.

Considerations for the Consumption of Vitamin and Mineral Supplements in Athlete Populations.

Vitamins and minerals are of fundamental importance to numerous human functions that are essential to optimise athlete performance. Athletes incur a high turnover of key vitamins and minerals and are therefore dependent on sufficient energy intake to replenish nutrient stores. However, many athletes are poor at servicing their energy replenishment needs, especially female athletes, and although a 'food first approach' to meeting nutrient requirements is the primary goal, it may be important for some athletes to consider a vitamin and/or mineral supplement to meet their daily needs. When working to determine if an athlete requires vitamin or mineral supplements, practitioners should use a robust framework to assess the overall energy requirements, current dietary practices and the biological and clinical status of their athletes. Of note, any supplementation plan should account for the various factors that may impact the efficacy of the approach (e.g. athlete sex, the nutrient recommended dietary intake, supplement dose/timing, co-consumption of other foods and any food-drug interactions). Importantly, there are numerous vitamins and minerals of key importance to athletes, each having specific relevance to certain situations (e.g. iron and B vitamins are significant contributors to haematological adaptation, calcium and vitamin D are important to bone health and folate is important in the female athlete); therefore, the appropriate supplement for a given situation should be carefully considered and consumed with the goal to augment an athlete's diet.

Female Athlete Representation and Dietary Control Methods Among Studies Assessing Chronic Carbohydrate Approaches to Support Training.

The aim of this audit was to assess the representation of female athletes, dietary control methods, and gold standard female methodology that underpins the current guidelines for chronic carbohydrate (CHO) intake strategies for athlete daily training diets. Using a standardized audit, 281 studies were identified that examined high versus moderate CHO, periodized CHO availability, and/or low CHO, high fat diets. There were 3,735 total participants across these studies with only ∼16% of participants being women. Few studies utilized a design that specifically considered females, with only 16 studies (∼6%) including a female-only cohort and six studies (∼2%) with a sex-based comparison in their statistical procedure, in comparison to the 217 studies (∼77%) including a male-only cohort. Most studies (∼72%) did not provide sufficient information to define the menstrual status of participants, and of the 18 studies that did, optimal methodology for control of ovarian hormones was only noted in one study. While ∼40% of male-only studies provided all food and beverages to participants, only ∼20% of studies with a female-specific design used this approach for dietary control. Most studies did not implement strategies to ensure compliance to dietary interventions and/or control energy intake during dietary interventions. The literature that has contributed to the current guidelines for daily CHO intake is lacking in research that is specific to, or adequately addresses, the female athlete. Redressing this imbalance is of high priority to ensure that the female athlete receives evidence-based recommendations that consider her specific needs.

Short Severe Energy Restriction with Refueling Reduces Body Mass without Altering Training-Associated Performance Improvement.

PURPOSE: We investigated short-term (9 d) exposure to low energy availability (LEA) in elite endurance athletes during a block of intensified training on self-reported well-being, body composition, and performance. METHODS: Twenty-three highly trained race walkers undertook an ~3-wk research-embedded training camp during which they undertook baseline testing and 6 d of high energy/carbohydrate (HCHO) availability (40 kcal·kg FFM -1 ·d -1 ) before being allocated to 9 d continuation of this diet ( n = 10 M, 2 F) or a significant decrease in energy availability to 15 kcal·kg FFM -1 ·d -1 (LEA: n = 10 M, 1 F). A real-world 10,000-m race walking event was undertaken before (baseline) and after (adaptation) these phases, with races being preceded by standardized carbohydrate fueling (8 g·kg body mass [BM] -1 for 24 h and 2 g·kg BM -1 prerace meal). RESULTS: Dual-energy x-ray absorptiometry-assessed body composition showed BM loss (2.0 kg, P < 0.001), primarily due to a 1.6-kg fat mass reduction ( P < 0.001) in LEA, with smaller losses (BM = 0.9 kg, P = 0.008; fat mass = 0.9 kg, P < 0.001) in HCHO. The 76-item Recovery-Stress Questionnaire for Athletes, undertaken at the end of each dietary phase, showed significant diet-trial effects for overall stress ( P = 0.021), overall recovery ( P = 0.024), sport-specific stress ( P = 0.003), and sport-specific recovery ( P = 0.012). However, improvements in race performance were similar: 4.5% ± 4.1% and 3.5% ± 1.8% for HCHO and LEA, respectively ( P < 0.001). The relationship between changes in performance and prerace BM was not significant ( r = -0.08 [-0.49 to 0.35], P = 0.717). CONCLUSIONS: A series of strategically timed but brief phases of substantially restricted energy availability might achieve ideal race weight as part of a long-term periodization of physique by high-performance athletes, but the relationship between BM, training quality, and performance in weight-dependent endurance sports is complicated.

Fueling the Female Athlete: Auditing Her Representation in Studies of Acute Carbohydrate Intake for Exercise.

PURPOSE: The aim of this audit was to assess the representation of female athletes within the literature that has led to current guidelines for carbohydrate (CHO) intake in the acute periods surrounding exercise and the quality of this research. METHODS: We conducted a standardized audit of research assessing CHO loading protocols, CHO mouth rinse, and CHO intake before, during, and after exercise. RESULTS: A total of 937 studies were identified in this audit. There were a total of 11,202 participants across these studies, with only ~11% being women. Most studies involved male-only cohorts (~79%), with a mere 38 studies (~4%) involving female-only cohorts and 14 studies (~2%) including a methodological design for comparison of sex-based responses. The frequent use of incorrect terminology surrounding menstrual status and the failure of most studies (~69%) to provide sufficient information on the menstrual status of participants suggests incomplete understanding and concern for female-specific considerations among researchers. Of the 197 studies that included women, only 13 (~7%) provided evidence of acceptable methodological control of ovarian hormones, and no study met all best-practice recommendations. Of these 13 studies, only half also provided sufficient information regarding the athletic caliber of participants. The topics that received such scrutiny were CHO loading protocols and CHO intake during exercise. CONCLUSIONS: The literature that underpins the current guidelines for CHO intake in the acute periods around exercise is lacking in high-quality research that can contribute knowledge specific to the female athlete and sex-based differences. New research that considers ovarian hormones and sex-based differences is needed to ensure that the recommendations for acute CHO fueling provided to female athletes are evidence based.

The Impact of Acute Calcium Intake on Bone Turnover Markers during a Training Day in Elite Male Rowers.

INTRODUCTION: Although an acute exercise session typically increases bone turnover markers (BTM), the impact of subsequent sessions and the interaction with preexercise calcium intake remain unclear despite the application to the "real-life" training of many competitive athletes. METHODS: Using a randomized crossover design, elite male rowers ( n = 16) completed two trials, a week apart, consisting of two 90-min rowing ergometer sessions (EX1, EX2) separated by 150 min. Before each trial, participants consumed a high (CAL; ~1000 mg) or isocaloric low (CON; <10 mg) calcium meal. Biochemical markers including parathyroid hormone (PTH), serum ionized calcium (iCa) and BTMs (C-terminal telopeptide of type I collagen, osteocalcin) were monitored from baseline to 3 h after EX2. RESULTS: Although each session caused perturbances of serum iCa, CAL maintained calcium concentrations above those of CON for most time points, 4.5% and 2.4% higher after EX1 and EX2, respectively. The decrease in iCa in CON was associated with an elevation of blood PTH ( P < 0.05) and C-terminal telopeptide of type I collagen ( P < 0.0001) over this period of repeated training sessions and their recovery, particularly during and after EX2. Preexercise intake of calcium-rich foods lowered BTM over the course of a day with several training sessions. CONCLUSIONS: Preexercise intake of a calcium-rich meal before training sessions undertaken within the same day had a cumulative and prolonged effect on the stabilization of blood iCa during exercise. In turn, this reduced the postexercise PTH response, potentially attenuating the increase in markers of bone resorption. Such practical strategies may be integrated into the athlete's overall sports nutrition plan, with the potential to safeguard long-term bone health and reduce the risk of bone stress injuries.

Managing Female Athlete Health: Auditing the Representation of Female versus Male Participants among Research in Supplements to Manage Diagnosed Micronutrient Issues.

Micronutrient deficiencies and sub-optimal intakes among female athletes are a concern and are commonly prevented or treated with medical supplements. However, it is unclear how well women have been considered in the research underpinning current supplementation practices. We conducted an audit of the literature supporting the use of calcium, iron, and vitamin D. Of the 299 studies, including 25,171 participants, the majority (71%) of participants were women. Studies with exclusively female cohorts (37%) were also more prevalent than those examining males in isolation (31%). However, study designs considering divergent responses between sexes were sparse, accounting for 7% of the literature. Moreover, despite the abundance of female participants, the quality and quantity of the literature specific to female athletes was poor. Just 32% of studies including women defined menstrual status, while none implemented best-practice methodologies regarding ovarian hormonal control. Additionally, only 10% of studies included highly trained female athletes. Investigations of calcium supplementation were particularly lacking, with just two studies conducted in highly trained women. New research should focus on high-quality investigations specific to female athletes, alongside evaluating sex-based differences in the response to calcium, iron, and vitamin D, thus ensuring the specific needs of women have been considered in current protocols involving medical supplements.