Combined intermittent hypoxic exposure at rest and continuous hypoxic training can maintain elevated hemoglobin mass after a hypoxic camp.

Athletes use hypoxic living and training to increase hemoglobin mass (Hbmass), but Hbmass declines rapidly upon return to sea level. We investigated whether Intermittent Hypoxic Exposure (IHE) + Continuous Hypoxic Training (CHT) after return to sea level maintained elevated Hbmass, and if changes in Hbmass were transferred to changes in maximal oxygen uptake (V̇O2max) and exercise performance. Hbmass was measured in 58 endurance athletes before (PRE), after (POST1), and 30 days after (POST2) a 27 ± 4-day training camp in hypoxia (n=44, HYP) or at sea level (n=14, SL). After return to sea level, 22 athletes included IHE (2 h rest) + CHT (1 h training) into their training every third day for one month (HYPIHE+CHT), whereas the other 22 HYP athletes were not exposed to IHE or CHT (HYPSL). Hbmass increased from PRE to POST1 in both HYPIHE+CHT (4.4 ± 0.7%, mean ± SEM) and HYPSL (4.1 ± 0.6%) (both p<0.001). Compared to PRE, Hbmass at POST2 remained 4.2 ± 0.8% higher in HYPIHE+CHT (p<0.001) and1.9 ± 0.5% higher in HYPSL (p=0.023), indicating a significant difference between the groups (p=0.002). In SL, no significant changes were observed in Hbmass with mean alterations between -0.5% and 0.4%. V̇O2max and time to exhaustion during an incremental treadmill test (n=35) were elevated from PRE to POST2 only in HYPIHE+CHT (5.8 ± 1.2% and 5.4 ± 1.4%, respectively, both p<0.001). IHE+CHT possesses the potential to mitigate the typical decline in Hbmass commonly observed during the initial weeks after return to sea level.

Beyond Menstrual Dysfunction: Does Altered Endocrine Function Caused by Problematic Low Energy Availability Impair Health and Sports Performance in Female Athletes?

Low energy availability, particularly when problematic (i.e., prolonged and/or severe), has numerous negative consequences for health and sports performance as characterized in relative energy deficiency in sport. These consequences may be driven by disturbances in endocrine function, although scientific evidence clearly linking endocrine dysfunction to decreased sports performance and blunted or diminished training adaptations is limited. We describe how low energy availability-induced changes in sex hormones manifest as menstrual dysfunction and accompanying hormonal dysfunction in other endocrine axes that lead to adverse health outcomes, including negative bone health, impaired metabolic activity, undesired outcomes for body composition, altered immune response, problematic cardiovascular outcomes, iron deficiency, as well as impaired endurance performance and force production, all of which ultimately may influence athlete health and performance. Where identifiable menstrual dysfunction indicates hypothalamic-pituitary-ovarian axis dysfunction, concomitant disturbances in other hormonal axes and their impact on the athlete's health and sports performance must be recognized as well. Given that the margin between podium positions and "losing" in competitive sports can be very small, several important questions regarding low energy availability, endocrinology, and the mechanisms behind impaired training adaptations and sports performance have yet to be explored.

Perspectives on Concurrent Strength and Endurance Training in Healthy Adult Females: A Systematic Review.

BACKGROUND: Both strength and endurance training are included in global exercise recommendations and are the main components of training programs for competitive sports. While an abundance of research has been published regarding concurrent strength and endurance training, only a small portion of this research has been conducted in females or has addressed their unique physiological circumstances (e.g., hormonal profiles related to menstrual cycle phase, menstrual dysfunction, and hormonal contraceptive use), which may influence training responses and adaptations. OBJECTIVE: The aim was to complete a systematic review of the scientific literature regarding training adaptations following concurrent strength and endurance training in apparently healthy adult females. METHODS: A systematic electronic search for articles was performed in July 2021 and again in December 2022 using PubMed and Medline. This review followed, where applicable, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The quality of the included studies was assessed using a modified Downs and Black checklist. Inclusion criteria were (1) fully published peer-reviewed publications; (2) study published in English; (3) participants were healthy normal weight or overweight females of reproductive age (mean age between > 18 and < 50) or presented as a group (n > 5) in studies including both females and males and where female results were reported separately; (4) participants were randomly assigned to intervention groups, when warranted, and the study included measures of maximal strength and endurance performance; and (5) the duration of the intervention was ≥ 8 weeks to ensure a meaningful training duration. RESULTS: Fourteen studies met the inclusion criteria (seven combined strength training with running, four with cycling, and three with rowing or cross-country skiing). These studies indicated that concurrent strength and endurance training generally increases parameters associated with strength and endurance performance in female participants, while several other health benefits such as, e.g., improved body composition and blood lipid profile were reported in individual studies. The presence of an "interference effect" in females could not be assessed from the included studies as this was not the focus of any included research and single-mode training groups were not always included alongside concurrent training groups. Importantly, the influence of concurrent training on fast-force production was limited, while the unique circumstances affecting females were not considered/reported in most studies. Overall study quality was low to moderate. CONCLUSION: Concurrent strength and endurance training appears to be beneficial in increasing strength and endurance capacity in females; however, multiple research paradigms must be explored to better understand the influence of concurrent training modalities in females. Future research should explore the influence of concurrent strength and endurance training on fast-force production, the possible presence of an "interference effect" in athletic populations, and the influence of unique circumstances, such as hormone profile, on training responses and adaptations.

Effect of menstrual cycle and contraceptive pill phase on aspects of exercise physiology and athletic performance in female athletes: protocol for the Feminae international multisite innovative project.

The idiom 'more high-quality research is needed' has become the slogan for sport and exercise physiology-based research in female athletes. However, in most instances, it is challenging to address this gap of high-quality research in elite female athletes at a single study site due to challenges in recruiting enough participants with numerous menstrual cycle and contraceptive pill permutations. Accordingly, we have assembled an international multisite team to undertake an innovative project for female athletes, which investigates the effects of changes in endogenous and exogenous oestrogen and progesterone/progestins across the menstrual cycle and in response to second-generation combined monophasic contraceptive pill use, on aspects of exercise physiology and athletic performance. This project will employ the current gold-standard methodologies in this area, resulting in an adequately powered dataset. This protocol paper describes the consortium-based approach we will undertake during this study.

Carbohydrate intake in young female cross-country skiers is lower than recommended and affects competition performance.

Purpose: (1) To evaluate if energy availability (EA), macronutrient intake and body composition change over four training periods in young, highly trained, female cross-country skiers, and (2) to clarify if EA, macronutrient intake, body composition, and competition performance are associated with each other in this cohort. Methods: During a one-year observational study, 25 female skiers completed 3-day food and training logs during four training periods: preparation, specific preparation, competition, and transition periods. A body composition measurement (bioimpedance analyzer) was performed at the end of the preparation, specific preparation, and competition periods. Competition performance was determined by International Ski Federation (FIS) points gathered from youth national championships. Results: EA (36-40 kcal·kg FFM-1·d-1) and carbohydrate (CHO) intake (4.4-5.1 g·kg-1·d-1) remained similar, and at a suboptimal level, between training periods despite a decrease in exercise energy expenditure (p = 0.002) in the transition period. Higher EA (r = -0.47, p = 0.035) and CHO intake (r = -0.65, p = 0.002) as well as lower FM (r = 0.60, p = 0.006) and F% (r = 0.57, p = 0.011) were associated with lower (better) FIS-points. CHO intake was the best predictor of distance competition performance (R2 = 0.46, p = 0.004). Conclusions: Young female cross-country skiers had similar EA and CHO intake over four training periods. Both EA and CHO intake were at suboptimal levels for performance and recovery. CHO intake and body composition are important factors influencing competition performance in young female cross-country skiers.

Nutritional intake and anthropometric characteristics are associated with endurance performance and markers of low energy availability in young female cross-country skiers.

BACKGROUND: Low energy availability (LEA) can have negative performance consequences, but the relationships between LEA and performance are poorly understood especially in field conditions. In addition, little is known about the contribution of macronutrients to long-term performance. Therefore, the aim of this study was to evaluate if energy availability (EA) and macronutrient intake in a field-based situation were associated with laboratory-measured performance, anthropometric characteristics, blood markers, training volume, and/or questionnaire-assessed risk of LEA in young female cross-country (XC) skiers. In addition, the study aimed to clarify which factors explained performance. METHODS: During a one-year observational study, 23 highly trained female XC skiers and biathletes (age 17.1 ± 1.0 years) completed 3-day food and training logs on four occasions (September-October, February-March, April-May, July-August). Mean (±SD) EA and macronutrient intake from these 12 days were calculated to describe yearly overall practices. Laboratory measurements (body composition with bioimpedance, blood hormone concentrations, maximal oxygen uptake (VO2max), oxygen uptake (VO2) at 4 mmol·L-1 lactate threshold (OBLA), double poling (DP) performance (time to exhaustion), counter movement jump (height) and the Low Energy Availability in Females Questionnaire (LEAF-Q)) were completed at the beginning (August 2020, M1) and end of the study (August 2021, M2). Annual training volume between measurements was recorded using an online training diary. RESULTS: The 12-day mean EA (37.4 ± 9.1 kcal·kg FFM-1·d-1) and carbohydrate (CHO) intake (4.8 ± 0.8 g·kg-1·d-1) were suboptimal while intake of protein (1.8 ± 0.3 g·kg-1·d-1) and fat (31 ± 4 E%) were within recommended ranges. Lower EA and CHO intake were associated with a higher LEAF-Q score (r = 0.44, p = 0.042; r = 0.47, p = 0.026). Higher CHO and protein intake were associated with higher VO2max (r = 0.61, p = 0.005; r = 0.54, p = 0.014), VO2 at OBLA (r = 0.63, p = 0.003; r = 0.62, p = 0.003), and DP performance at M2 (r = 0.42, p = 0.051; r = 0.44, p = 0.039). Body fat percentage (F%) was negatively associated with CHO and protein intake (r = -0.50, p = 0.017; r = -0.66, p = 0.001). Better DP performance at M2 was explained by higher training volume (R2 = 0.24, p = 0.033) and higher relative VO2max and VO2 at OBLA at M2 by lower F% (R2 = 0.44, p = 0.004; R2 = 0.47, p = 0.003). Increase from M1 to M2 in DP performance was explained by a decrease in F% (R2 = 0.25, p = 0.029). CONCLUSIONS: F%, and training volume were the most important factors explaining performance in young female XC skiers. Notably, lower F% was associated with higher macronutrient intake, suggesting that restricting nutritional intake may not be a good strategy to modify body composition in young female athletes. In addition, lower overall CHO intake and EA increased risk of LEA determined by LEAF-Q. These findings highlight the importance of adequate nutritional intake to support performance and overall health.

Hemoglobin mass and performance responses during 4 weeks of normobaric "live high-train low and high".

PURPOSE: To investigate whether 4 weeks of normobaric "live high-train low and high" (LHTLH) causes different hematological, cardiorespiratory, and sea-level performance changes compared to living and training in normoxia during a preparation season. METHODS: Nineteen (13 women, 6 men) cross-country skiers competing at the national or international level completed a 28-day period (∼18 h day-1 ) of LHTLH in normobaric hypoxia of ∼2400 m (LHTLH group) including two 1 h low-intensity training sessions per week in normobaric hypoxia of 2500 m while continuing their normal training program in normoxia. Hemoglobin mass (Hbmass ) was assessed using a carbon monoxide rebreathing method. Time to exhaustion (TTE) and maximal oxygen uptake (VO2max ) were measured using an incremental treadmill test. Measurements were completed at baseline and within 3 days after LHTLH. The control group skiers (CON) (seven women, eight men) performed the same tests while living and training in normoxia with ∼4 weeks between the tests. RESULTS: Hbmass in LHTLH increased 4.2 ± 1.7% from 772 ± 213 g (11.7 ± 1.4 g kg-1 ) to 805 ± 226 g (12.5 ± 1.6 g kg-1 ) (p < 0.001) while it was unchanged in CON (p = 0.21). TTE improved during the study regardless of the group (3.3 ± 3.4% in LHTLH; 4.3 ± 4.8% in CON, p < 0.001). VO2max did not increase in LHTLH (61.2 ± 8.7 mL kg-1 min-1 vs. 62.1 ± 7.6 mL kg-1 min-1 , p = 0.36) while a significant increase was detected in CON (61.3 ± 8.0-64.0 ± 8.1 mL kg-1 min-1 , p < 0.001). CONCLUSIONS: Four-week normobaric LHTLH was beneficial for increasing Hbmass but did not support the short-term development of maximal endurance performance and VO2max when compared to the athletes who lived and trained in normoxia.

Nocturnal Heart Rate Variability in Women Discordant for Hormonal Contraceptive Use.

PURPOSE: The aim of this study was to investigate within-cycle differences in nocturnal heart rate (HR) and heart rate variability (HRV) in naturally menstruating women (NM) and women using combined hormonal contraceptives (CU) or progestin-only hormonal contraceptives (PU). METHODS: Physically active participants were recruited into three groups: NM ( n = 19), CU ( n = 11), and PU ( n = 12). Participants' HR and HRV (with Bodyguard 2 HRV monitor) and blood hormones were monitored during one menstrual cycle (MC) (NM group) or for 4 wk (CU and PU groups). Estradiol, progesterone, and luteinizing hormone were analyzed from fasting blood samples collected four times in the NM (M1 = bleeding, M2 = follicular phase, M3 = ovulation, and M4 = luteal phase) and PU groups (M1 = lowest E 2 , M2 = M1 + 7 d, M3 = M1 + 14 d, and M4 = M1 + 21 d) and twice in the CU group (active and inactive pill phases). After every blood sample, nightly HR and HRV were recorded and examined as an average from two nights. RESULTS: Hormonal concentrations differed ( P < 0.05) between MC phases in the NM and PU groups, but not ( P ≥ 0.116) between the active and the inactive phases in the CU group. In the NM and PU groups, some of the HRV values were higher, whereas in the NM group, HR was lower during M2 compared with M3 ( P < 0.049) and M4 ( P < 0.035). In the CU group, HRV values ( P = 0.014-0.038) were higher, and HR was lower ( P = 0.038) in the inactive phase compared with the first week of the active phase. CONCLUSIONS: The MC and the hormonal cycle phases influence autonomic nervous system balance, which is reflected in measurements of nocturnal HR and HRV. This should be considered when monitoring recovery in physically active individuals.

Self-Reported Restrictive Eating, Eating Disorders, Menstrual Dysfunction, and Injuries in Athletes Competing at Different Levels and Sports.

The purpose of this study was to investigate the prevalence of self-reported restrictive eating, current or past eating disorder, and menstrual dysfunction and their relationships with injuries. Furthermore, we aimed to compare these prevalences and associations between younger (aged 15-24) and older (aged 25-45) athletes, between elite and non-elite athletes, and between athletes competing in lean and non-lean sports. Data were collected using a web-based questionnaire. Participants were 846 female athletes representing 67 different sports. Results showed that 25%, 18%, and 32% of the athletes reported restrictive eating, eating disorders, and menstrual dysfunction, respectively. Higher rates of lean sport athletes compared with non-lean sport athletes reported these symptoms, while no differences were found between elite and non-elite athletes. Younger athletes reported higher rates of menstrual dysfunction and lower lifetime prevalence of eating disorders. Both restrictive eating (OR 1.41, 95% CI 1.02-1.94) and eating disorders (OR 1.89, 95% CI 1.31-2.73) were associated with injuries, while menstrual dysfunction was associated with more missed participation days compared with a regular menstrual cycle (OR 1.79, 95% CI 1.05-3.07). Our findings indicate that eating disorder symptoms and menstrual dysfunction are common problems in athletes that should be managed properly as they are linked to injuries and missed training/competition days.

Influence of Menstrual Cycle or Hormonal Contraceptive Phase on Energy Intake and Metabolic Hormones-A Pilot Study.

Sex hormones are suggested to influence energy intake (EI) and metabolic hormones. This study investigated the influence of menstrual cycle (MC) and hormonal contraceptive (HC) cycle phases on EI, energy availability (EA), and metabolic hormones in recreational athletes (eumenorrheic, NHC = 15 and monophasic HC-users, CHC = 9). In addition, 72-h dietary and training logs were collected in addition to blood samples, which were analyzed for 17ß-estradiol (E2), progesterone (P4), leptin, total ghrelin, insulin, and tri-iodothyronine (T3). Measurements were completed at four time-points (phases): Bleeding, mid-follicular (FP)/active 1, ovulation (OVU)/active 2, mid-luteal (LP)/inactive in NHC/CHC, respectively. As expected, E2 and P4 fluctuated significantly in NHC (p < 0.05) and remained stable in CHC. In NHC, leptin increased significantly between bleeding and ovulation (p = 0.030) as well as between FP and OVU (p = 0.022). No group differences in other measured hormones were observed across the MC and HC cycle. The mean EI and EA were similar between phases, with no significant differences observed in macronutrient intake over either the MC or HC. While the MC phase might have a small, but statistically significant effect on leptin, the findings of the present study suggest that the MC or HC phase does not significantly alter ad libitum EI or EA in recreational athletes.

Influence of Menstrual Cycle or Hormonal Contraceptive Phase on Physiological Variables Monitored During Treadmill Testing.

Purpose: To examine the influence of menstrual cycle (MC) and hormonal contraceptive (HC) cycle phases on physiological variables monitored during incremental treadmill testing in physically active women (eumenorrheic, EUM = 16 and monophasic HC-users, CHC = 12). Methods: Four running tests to exhaustion were performed at bleeding, mid follicular (mid FOL)/active 1, ovulation/active 2, and mid luteal (mid LUT)/inactive. HC and MC phases were confirmed from serum hormones. Heart rate (HR), blood lactate (Bla), and V ˙ O2 were monitored, while aerobic (AerT) and anaerobic (AnaT) thresholds were determined. V ˙ O2peak, maximal running speed (RUNpeak), and total running time (RUNtotal) were recorded. Results: No significant changes were observed in V ˙ O2 or Bla at AerT or AnaT across phases in either group. At maximal effort, absolute and relative V ˙ O2peak, RUNpeak, and RUNtotal remained stable across phases in both groups. No significant fluctuations in HRmax were observed across phases, but HR at both AerT and AnaT tended to be lower in EUM than in CHC across phases. Conclusion: Hormonal fluctuations over the MC and HC do not systematically influence physiological variables monitored during incremental treadmill testing. Between group differences in HR at AerT and AnaT underline why HR-based training should be prescribed individually, while recording of MC or HC use when testing should be encouraged as phase may explain minor, but possibly meaningful, changes in, e.g., Bla concentrations or differences in HR response.