Risk and prevalence of Relative Energy Deficiency in Sport (REDs) among professional female football players.

A high prevalence of low energy availability (LEA) has been reported in female football players. This is of concern as problematic LEA may evolve into a syndromic pattern known as relative energy deficiency in sport (REDs). Given the difficulties in accurately assessing LEA, our study shifts emphasis to measurable indicators of REDs, serving as proxies for health detriments caused by LEA. The present cross-sectional study aimed to quantify the risk of REDs and to assess the prevalence of indicators indicative of the syndrome. 60 players (tiers 3 and 4) from three Norwegian football teams were analyzed as a single cohort but also stratified based on player position and menstrual status. The proportion of players at risk for REDs was 22%, that is, 17% with mild, 3% with moderate to high, and 2% with very high/extreme risk, respectively. The majority of the cohort (71%) presented with no primary indicators, while 20%, 7%, and 2% presented with one, two, and three primary indicators, respectively. Regarding secondary indicators, 57% had none, 33% had one, and 10% had two indicators. For associated indicators, 30% had none, 42% had one, 18% had two, 8% had three, and 2% had four indicators. Player position did not affect the prevalence of REDs indicators. Among noncontraceptive users (n = 27), secondary amenorrhea (AME) was reported by 30%. These findings indicate that health and performance teams should prioritize universal health promoting strategies rather than selective or indicative strategies. Particularly, focus on nutritional periodization to secure sufficient energy availability, mitigating the risk of problematic LEA and REDs should be addressed.

FIDES Athlete Development Programme: project background and study protocol of an embedded multiple case study.

Most sports science research revolves around male subjects. As a result, most of the knowledge and practices within sports are male-centric. Failing to take the biological, psychological and social (biopsychosocial) particularities of females into account is believed to hinder optimal sports participation, development and performance, with potential negative effects on the health and well-being of females. To close the knowledge gap and alleviate these issues, we aim to develop and evaluate a 12-video educational intervention that addresses female-specific subject matter: the FIDES Athlete Development Programme. The study is designed as an embedded multiple case study where at least 1320 Swedish female athletes aged 13-16 will participate, in addition to their parents and their coaches. The girls will be recruited through their sports clubs, with half being exposed to the FIDES Athlete Development Programme and the other half serving as control cases. The primary outcomes are well-being and sporting experience. To further increase our understanding of the intervention and its implications, interviews and focus group interviews with a reference group of girls and focus group interviews with a randomly selected subsample of coaches and parents will also be performed. The project is approved by the Swedish ethics committee (number: 2023-05264-01) and will be carried out in compliance with the Declaration of Helsinki. Results from the project will be published open access in peer-reviewed journals, at national and international conferences, in mass media, and a PhD thesis. The anonymised data will be made openly available in a data repository.

Direct and indirect impact of low energy availability on sports performance.

Low energy availability (LEA) occurs inadvertently and purposefully in many athletes across numerous sports; and well planned, supervised periods with moderate LEA can improve body composition and power to weight ratio possibly enhancing performance in some sports. LEA however has the potential to have negative effects on a multitude of physiological and psychological systems in female and male athletes. Systems such as the endocrine, cardiovascular, metabolism, reproductive, immune, mental perception, and motivation as well as behaviors can all be impacted by severe (serious and/or prolonged or chronic) LEA. Such widely diverse effects can influence the health status, training adaptation, and performance outcomes of athletes leading to both direct changes (e.g., decreased strength and endurance) as well as indirect changes (e.g., reduced training response, increased risk of injury) in performance. To date, performance implications have not been well examined relative to LEA. Therefore, the intent of this narrative review is to characterize the effects of short-, medium-, and long-term exposure to LEA on direct and indirect sports performance outcomes. In doing so we have focused both on laboratory settings as well as descriptive athletic case-study-type experiential evidence.

Risk factors for sexual harassment and abuse victimization among adolescent athletes and non-athletes: A one-year follow-up study.

BACKGROUND: The association between SHA and negative mental health increases the need to understand risk factors for SHA victimization, which is important for future development of prevention programs. OBJECTIVE: To examine which combinations of demographic- and mental health factors were associated with subsequent SHA victimization, and the prevalence of elite athletes, recreational athletes, and reference students who experienced sexual revictimization. PARTICIPANTS AND SETTING: Norwegian elite athletes and recreational athletes attending sport high schools, and reference students attending non-sport high schools (mean age: 17.1 years) were eligible for participation. METHODS: The participants answered an online questionnaire at two measurement points one year apart, T1 and T2 (n = 1139, 51.1 % girls). After testing for measurement invariance, data were analyzed with Classification and Regression Tree analysis (CRT) using demographic- and mental health variables from T1 as independent variables, and SHA at T2 as outcome. RESULTS: The combination of being a girl with high level of symptoms of eating disorders and other psychological symptoms was associated with subsequent reporting of SHA. Among the students with lifetime experience of SHA at T1 (n = 533, 58.3 %), 49.5 % reported revictimization at T2 (60.9 % girls, 32.2 % boys, p ≤ .001). The prevalence of SHA revictimization was lower among elite athletes (44.3 %) compared with recreational athletes (49.1 %) and reference students (59.4 %, p = .019). CONCLUSION: The combination of female gender and mental health symptoms are risk factors for subsequent SHA victimization. These findings, and the high prevalence of SHA revictimization is important knowledge for developing preventive programs targeting elite athletes, recreational athletes, and reference students.

Relative Energy Deficiency in Sport (REDs) Indicators in Male Adolescent Endurance Athletes: A 3-Year Longitudinal Study.

Longitudinal measurements of Relative Energy Deficiency in Sport (REDs) among adolescent male elite athletes are lacking. We aimed to monitor REDs indicators and their possible impact on performance in elite high-school cross-country skiing and biathlon athletes (n = 13) (16.3 ± 0.4 years, 179.4 ± 7.6 cm, 63.6 ± 8.2 kg body mass (BM), and peak oxygen uptake (VO2peak): 61.5 ± 5.3 mL/kg BM/min) every 6 months for 3 years. Protocols included assessments of energy availability (EA), body composition and bone mineral density (BMD), resting metabolic rate (RMR), disordered eating behavior, exercise addiction, VO2peak, and muscle strength. Data were analyzed using a linear mixed model. At baseline, 38% had low lumbar BMD (Z-score ≤ -1), and overall, bone health increased only slightly. VO2peak and muscle strength improved (p < 0.001), RMR decreased (p = 0.016), and no change was observed in EA or physiological or psychological REDs indicators. Conclusively, many of these young male athletes had poor bone health at baseline, and most either lost or did not achieve the expected pubertal bone mineral accrual, although no other indication of REDs was observed, while performance improved during the study period. Our findings highlight the importance of elite sports high schools focusing on screening for early detection of impaired bone health in male athletes.

Primary, secondary and tertiary prevention of Relative Energy Deficiency in Sport (REDs): a narrative review by a subgroup of the IOC consensus on REDs.

Relative Energy Deficiency in Sport (REDs) is common among female and male athletes representing various sports at different performance levels, and the underlying cause is problematic low energy availability (LEA). It is essential to prevent problematic LEA to decrease the risk of serious health and performance consequences. This narrative review addresses REDs primary, secondary and tertiary prevention strategies and recommends best practice prevention guidelines targeting the athlete health and performance team, athlete entourage (eg, coaches, parents, managers) and sport organisations. Primary prevention of REDs seeks to minimise exposure to and reduce behaviours associated with problematic LEA. Some of the important strategies are educational initiatives and de-emphasising body weight and leanness, particularly in young and subelite athletes. Secondary prevention encourages the early identification and management of REDs signs or symptoms to facilitate early treatment to prevent development of more serious REDs outcomes. Recommended strategies for identifying athletes at risk are self-reported screening instruments, individual health interviews and/or objective assessment of REDs markers. Tertiary prevention (clinical treatment) seeks to limit short-term and long-term severe health consequences of REDs. The cornerstone of tertiary prevention is identifying the source of and treating problematic LEA. Best practice guidelines to prevent REDs and related consequences include a multipronged approach targeting the athlete health and performance team, the athlete entourage and sport organisations, who all need to ensure a supportive and safe sporting environment, have sufficient REDs knowledge and remain observant for the early signs and symptoms of REDs.

2023 International Olympic Committee's (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs).

Relative Energy Deficiency in Sport (REDs) was first introduced in 2014 by the International Olympic Committee's expert writing panel, identifying a syndrome of deleterious health and performance outcomes experienced by female and male athletes exposed to low energy availability (LEA; inadequate energy intake in relation to exercise energy expenditure). Since the 2018 REDs consensus, there have been >170 original research publications advancing the field of REDs science, including emerging data demonstrating the growing role of low carbohydrate availability, further evidence of the interplay between mental health and REDs and more data elucidating the impact of LEA in males. Our knowledge of REDs signs and symptoms has resulted in updated Health and Performance Conceptual Models and the development of a novel Physiological Model. This Physiological Model is designed to demonstrate the complexity of either problematic or adaptable LEA exposure, coupled with individual moderating factors, leading to changes in health and performance outcomes. Guidelines for safe and effective body composition assessment to help prevent REDs are also outlined. A new REDs Clinical Assessment Tool-Version 2 is introduced to facilitate the detection and clinical diagnosis of REDs based on accumulated severity and risk stratification, with associated training and competition recommendations. Prevention and treatment principles of REDs are presented to encourage best practices for sports organisations and clinicians. Finally, methodological best practices for REDs research are outlined to stimulate future high-quality research to address important knowledge gaps.

Sexual harassment and abuse; disclosure and awareness of report- and support resources in Norwegian sport- and non-sport high schools: a prospective exploratory study.

Purpose: To examine high school students' disclosure of sexual harassment and abuse (SHA), and awareness of reporting systems and support mechanisms in school among students, leaders, and coaches. Method: Norwegian 17-year-old high school elite athletes (n = 630), recreational athletes (n = 307), and reference students (n = 263) responded to an online questionnaire at two measurement points, 1 year apart (T1 and T2). Leaders and coaches (n = 249) at the participating high schools responded to an adapted version of the questionnaire at T1. Data were analyzed using ANOVA or Welch test, Pearson Chi-Square test, and McNemar test. Results: In total, 11.4 and 34.0% of the adolescents were aware of reporting systems and support mechanisms, respectively, in their schools. Nearly all the leaders, and half of the coaches were aware of these resources. Among the adolescents with lifetime experience of SHA, 20.1% had disclosed their experiences to someone. Girls disclosed more frequently than boys. The elite- and recreational athletes disclosed less often compared with the reference students. A negative change from T1 to T2 was found in disclosure of SHA and awareness of support mechanisms. At T2, 6.5% of the adolescents reported that their school had implemented measures against SHA during the last 12 months. Conclusion: The results emphasize a need for institutional effort to improve information about available report- and support resources and increase the relevance of use of such systems for adolescents.

The Healthy Body Image Intervention and Reduction in Eating Disorder Symptomatology and Muscle Building Supplement Use in High School Students: A Study of Mediating Factors.

Background: Mediation analysis is important to test the theoretical framework underpinning an intervention. We therefore aimed to investigate if the healthy body image (HBI) intervention's effect on eating disorder (ED) symptomatology and use of muscle building supplements was mediated by the change in risk and protective factors for ED development and muscle building supplement use. Methods: This study used data from the HBI intervention: a cluster randomized controlled universal intervention aiming to promote positive body image and embodiment and reduce the risk for ED development including 30 schools in Norway. A total of 1,713 (37% boys) participants were included in the analyses. Conditional latent growth curve analyses were performed to test for indirect effects on ED symptomatology and weekly frequency of protein and creatine supplement use measured at the 12-month follow-up via change in the proposed mediators. Results: In girls, the reduction in ED symptomatology was mediated by positive changes in protective factors (self-esteem and body image flexibility) and reductions in risk factor scores (perceived media pressure and thin appearance internalization). Comparable changes in protective and risk factors among boys played no mediating role. Conclusion: Interventions aiming to reduce the risk of ED development in girls may benefit from aiming to enhance self-esteem and body image flexibility and reduce perceived media pressure and thin appearance internalization. Future studies should investigate the casual relationship between muscle building supplement use and risk and protective factors for ED development in both girls and boys.

Sexual Harassment and Abuse among Young Elite Athletes, Recreational Athletes, and Reference Students: A Prospective Study.

PURPOSE: This study aimed to examine the 12-month prevalence and 12-month prospective change in reported sexual harassment and abuse (SHA) victimization among young elite athletes, recreational athletes, and reference students in three different social settings and to identify the perpetrators. METHODS: In total, 919 adolescents responded to an online questionnaire in 12th grade (T1) and 13th grade (T2). The sample consisted of elite athletes ( n = 482) and recreational athletes ( n = 233) attending Norwegian elite sport high schools ( n = 26), and reference students ( n = 200) attending ordinary high schools with no sport specialization ( n = 6). Data were analyzed using independent-sample t -test, Pearson χ 2 for independence/Fisher's exact test, McNemar test, and logistic regression analysis. RESULTS: The total 12-month prevalence of SHA was 38.6% at T1 and 35.1% at T2. Most of the participants (74.6%-85.0%) reported no change in SHA from T1 to T2. The prevalence of SHA was higher for girls compared with boys, and elite athletes reported less SHA than recreational athletes and reference students, respectively. SHA occurred most often in a free time setting. Verbal sexual harassment, nonverbal sexual harassment, and physical SHA were reported by 24.6%, 27.0%, and 14.0%, respectively. Peers were reported as perpetrators by 83.1%, trainer/teacher/health personnel by 20.1%, and "other" perpetrators by 56.4%. CONCLUSIONS: Because one in three elite athletes and nearly one in two recreational athletes and reference students, respectively, reported SHA victimization within a 12-month period, well-targeted preventive measures are needed for both young athletes and nonathletes.

Risk of Low Energy Availability, Disordered Eating, Exercise Addiction, and Food Intolerances in Female Endurance Athletes.

Relative energy deficiency in sport (RED-S) is a complex syndrome describing health and performance consequences of low energy availability (LEA) and is common among female endurance athletes. Various underlying causes of LEA have been reported, including disordered eating behavior (DE), but studies investigating the association with exercise addiction and food intolerances are lacking. Therefore, the aim of this cross-sectional study was to investigate the association between DE, exercise addiction and food intolerances in athletes at risk of LEA compared to those with low risk. Female endurance athletes, 18-35 years, training ≥5 times/week were recruited in Norway, Sweden, Ireland, and Germany. Participants completed an online-survey comprising the LEA in Females Questionnaire (LEAF-Q), Exercise Addiction Inventory (EAI), Eating Disorder Examination Questionnaire (EDE-Q), and questions regarding food intolerances. Of the 202 participants who met the inclusion criteria and completed the online survey, 65% were at risk of LEA, 23% were at risk of exercise addiction, and 21% had DE. Athletes at risk of LEA had higher EDE-Q and EAI scores compared to athletes with low risk. EAI score remained higher in athletes with risk of LEA after excluding athletes with DE. Athletes at risk of LEA did not report more food intolerances (17 vs. 10%, P = 0.198), but were more frequently reported by athletes with DE (28 vs. 11%, P = 0.004). In conclusion, these athletes had a high risk of LEA, exercise addiction, and DE. Exercise addiction should be considered as an additional risk factor in the prevention, early detection, and targeted treatment of RED-S among female endurance athletes.

Explanations for use of dietary- and muscle enhancing dietary supplements among university students: a national cross-sectional study.

BACKGROUND: Use of dietary supplements (DS) and muscle enhancing dietary supplements (MEDS) is frequent among students despite the lack of evidence of effects and health risks related to consumption. We need to increase our understanding of students' motivation, examine potential gender differences, and explore explanatory factors, to address preventive measures related to use. Therefore, this study aimed to explore the frequency of, and the reasons for, DS use among university students, as well as explanatory factors for use of MEDS. METHOD: Male and female students from nine Norwegian universities participated in this cross-sectional study. Participants responded to questions about demographics, DS and MEDS use, internalization of body ideals, physical activity- and exercise level, motives for exercise, and exercise context. Independent t-test, Chi-square test, Pearson's correlation, and logistic regression were used to investigate between group differences, associations, and explanatory factors for use, respectively. P-values ≤ 0.05 were defined as significant. RESULTS: A total of 1001 males (34%) and females, with a mean(sd) age of 24.21(4.76) years, participated. The frequency of DS use was 42% and 40% (p = .414) in males and females, respectively, in which more males than females used DS to improve physical or mental performance (p = < .001), increase muscle mass (p = < .001) and weight for health (p = .014), and improve appearance (p = < .001). In males and females, respectively, 25% and 10% used MEDS (p = < .001). In males, being a fitness center member (OR:3.80), exercising to improve muscle mass (OR:1.96), and a higher physical activity level (OR:1.09) positively explained MEDS use, while exercising to increase endurance (OR:0.49) and being an exercise science student (OR:0.47) negatively explained MEDS use. In females, internalizing the athletic body ideal (OR:1.78) and exercising to improve muscle mass (OR:1.74) positively explained MEDS use. CONCLUSIONS: Our main findings indicate that a surprisingly high percentage of male and female Norwegian students use DS and MEDS, and that reasons for use, and variables explaining the variability in frequency of use, differ between genders. Longitudinal studies to investigate direction of associations are needed in future research.

Protein, Creatine, and Dieting Supplements Among Adolescents: Use and Associations With Eating Disorder Risk Factors, Exercise-, and Sports Participation, and Immigrant Status.

Objective: This study aimed to estimate the number of weekly users of protein, creatine, and dieting supplements and to explore whether weekly use was related to eating disorder (ED) risk factors, exercise, sports participation, and immigrant status. Methods: In total, 629 and 1,060 high school boys and girls, respectively, self-reported weekly frequency of protein, creatine, and dieting supplement use, and weight and shape concerns, appearance internalization and pressure, self-esteem, mental distress, physical activity level, exercise context, and the type and weekly frequency of sport played. Multiple hierarchical regression analyses were performed to investigate explanatory factors for supplement use. Results: More boys than girls used protein and creatine supplements. Immigrant boys had more frequent use of all supplements than non-immigrant boys, and immigrant girls used creatine supplements more frequently than non-immigrant girls. In total, 23-40 and 5-6% of the variation in the weekly frequency of supplement use in boys and girls, respectively, was explained by immigrant status, ED risk factors, and exercise and sports participation. More frequent use of protein, creatine and dieting supplements in boys was significantly explained by more weight and shape concerns, fitness center exercise, and weight-sensitive sports participation. Depending on the type of supplement, more frequent use of supplements in girls was significantly explained by lower self-esteem, more engagement in weight-sensitive sports, and less engagement in general sport and exercise activities. Conclusion: Weekly supplement use was common and more frequent among boys than girls. The weekly use of protein, creatine, and dieting supplements was related to ED risk factors, exercise and sports participation, and immigrant status in boys but not in girls.

Prevalence of Surrogate Markers of Relative Energy Deficiency in Male Norwegian Olympic-Level Athletes.

The syndrome of Relative Energy Deficiency in Sport (RED-S) includes wide-ranging effects on physiological and psychological functioning, performance, and general health. However, RED-S is understudied among male athletes at the highest performance levels. This cross-sectional study aimed to investigate surrogate RED-S markers prevalence in Norwegian male Olympic-level athletes. Athletes (n = 44) aged 24.7 ± 3.8 years, body mass 81.3 ± 15.9 kg, body fat 13.7% ± 5.8%, and training volume 76.1 ± 22.9 hr/month were included. Assessed parameters included resting metabolic rate (RMR), body composition, and bone mineral density by dual-energy X-ray absorptiometry and venous blood variables (testosterone, free triiodothyronine, cortisol, and lipids). Seven athletes (16%) grouped by the presence of low RMR (RMRratio < 0.90) (0.81 ± 0.07 vs. 1.04 ± 0.09, p < .001, effect size 2.6), also showed lower testosterone (12.9 ± 5.3 vs. 19.0 ± 5.3 nmol/L, p = .020) than in normal RMR group. In low RMRratio individuals, prevalence of other RED-S markers (-subclinical-low testosterone, low free triiodothyronine, high cortisol, and elevated low-density lipoprotein) was (N/number of markers): 2/0, 2/1, 2/2, 1/3. Low bone mineral density (z-score < -1) was found in 16% of the athletes, all with normal RMR. Subclinical low testosterone and free triiodothyronine levels were found in nine (25%) and two (5%) athletes, respectively. Subclinical high cortisol was found in 23% of athletes while 34% had elevated low-density lipoprotein cholesterol levels. Seven of 12 athletes with two or more RED-S markers had normal RMR. In conclusion, this study found that multiple RED-S markers also exist in male Olympic-level athletes. This highlights the importance of regular screening of male elite athletes, to ensure early detection and treatment of RED-S.

Does organized sports participation in childhood and adolescence positively influence health? A review of reviews.

Sports participations have the potential for both positive and negative health outcomes. We hence aimed (i) to assess systematically reviewed associations between organized sports participation in children and adolescents and their health, and (ii) to assess qualitative syntheses of experiences among children and adolescents concerning organized sports participation and health. A search was undertaken in April 2020 across the databases MEDLINE, EMBASE, APA PsycInfo (Ovid), Scopus, SPORTDiscus (EBSCOhost), and specialized databases for reviews. The recommended Joanna Briggs Institute approach to critical appraisal, study selection, data extraction, and data synthesis was used. Systematic reviews were included that covered children and/or adolescents aged ≤ 18 years, and adult participants with retrospective exposure to-or experiences of-organized sports participation before the age of 19 and examining health outcomes and experiences (Prospero protocol CRD 42020206677). Five reviews based mainly on cross-sectional data, two mainly on longitudinal data, and one on experimental studies were included. A causal relationship of moderate-to-high level of evidence between organized sports participation and moderate crude weight reduction accentuated by diet control and team sports was identified. Evidence of causal relationships between sports participation and reduced anxiety, and depression and increased physical activity was at a moderate level. Evidence of causal relationships between sports participation and health was of low-to-moderate level concerning obesity status (inconclusive), bone health (positive), and psychological and social health (positive and negative). Causal relationships between organized child and adolescent sports participation and health remain uncertain. Experimental and well-conducted longitudinal primary studies are highly warranted.

Body appreciation and body appearance pressure in Norwegian university students comparing exercise science students and other students.

BACKGROUND: Body image is considered a core issue for public health and associates with university students' overall health. Due to positive associations between exercise and body image, it has been suggested that students within an exercise science program might be more body appreciative compared to other students. On the other hand, the strong societal idealization of the athletic body may expose them to a pressure of having a specific body appearance, which may result in unfavorable health consequences. Nevertheless, studies investigating these hypotheses are lacking. We therefore aimed to explore the level and associations of body appreciation, body appearance pressure, body image related mental health constructs, physical activity, and exercise, in Norwegian university exercise science and non-health reference students. METHOD: Male and female exercise science students (n = 517) and reference students (n = 476), from nine large universities in Norway took part in this cross-sectional study. Participants responded to the Body appreciation scale-2, a self-developed questionnaire on body appearance pressure, Physical Appearance Comparison Scale-Revised, Sociocultural attitudes towards appearance questionnaire-4R, Rosenberg Self-Esteem Scale, Satisfaction with Life Scale, and questions about physical activity and exercise. Between group differences were analyzed using student independent t-test and ANCOVA for parametric data and Chi-square test for categorical data, and associations were evaluated by Person's correlation. P-values ≤0.05 were defined as significant. RESULTS: Female exercise science students had higher scores on body appreciation compared to reference students. No group difference was found in males. A high percentage of students reported experiencing body appearance pressure, with 69 and 85% among male and female exercise science students, and 57 and 83% among male and female reference students. Fitness centers were the settings where most respondents experienced body appearance pressure. Body appreciation was strongly associated with favorable scores on body image related mental health constructs, while personally experienced body appearance pressure associated with destructive scores on the same constructs. CONCLUSION: Body appearance pressure is an issue among university students regardless of study program. Actions to promote body appreciation and prevent body appearance pressure may include an implementation of media literacy, body functionality, and exercise as topics within the education program to safeguard students' health and well-being. CLINICAL TRIAL REGISTRY: No. NCT04256967 .

The Norwegian healthy body image intervention promotes positive embodiment through improved self-esteem.

We examined both direct and indirect effects of the Healthy Body Image (HBI) intervention on positive embodiment among Norwegian high school students. In total, 2446 12th grade boys (43 %) and girls (mean age 16.8 years) from 30 schools participated in a cluster-randomized controlled study with the HBI intervention and a control condition as the study arms. We tested mediation models using path analysis and found that among several hypothesized mediators, only self-esteem mediated a positive intervention effect on positive embodiment for both boys and girls. A direct effect of the intervention on positive embodiment was only found in girls. The study provides novel findings indicating that health promotion interventions to address a positive embodiment should focus on enhancing adolescent's self-esteem. Serial mediation modeling might reveal more complex explanations of change mechanisms and could further evolve current knowledge.

Impact of a 4-Week Intensified Endurance Training Intervention on Markers of Relative Energy Deficiency in Sport (RED-S) and Performance Among Well-Trained Male Cyclists.

Cyclists often apply block periodization to high training volumes in meso- and macrocycles to optimize training adaptation and to prepare for competition. Body mass influences performance in many sports, including endurance disciplines, and conditions related to the syndrome Relative Energy Deficiency in Sports (RED-S) such as metabolic adaptations and premature osteoporosis have also been reported in male cyclists. This study aimed to determine how a 4-week mesocycle of intensified endurance training designed to increase performance, would affect markers of RED-S in well-trained male cyclists. Twenty-two participants (age: 33.5 ± 6.6 years, height: 181.4 ± 5.2 cm, weight: 76.5 ± 7.4 kg, peak oxygen uptake (VO2peak): 63.5 ± 6.6 mL·kg-1·min-1) were recruited and instructed to maintain their background training load and to follow a supervised training protocol consisting of three high-intensity interval training sessions per week with a work duration of 32 min per session. Protocols included pre- and postintervention assessment of resting metabolic rate (RMR) using a ventilated hood, body composition and bone health by dual-energy X-ray absorptiometry (DXA), blood samples, energy intake, and aerobic performance. The interval training increased participants' aerobic performance-peak power output [4.8%, p < 0.001], VO2peak [2.4%, p = 0.005], and functional threshold power [6.5%, p < 0.001] as well as total testosterone levels [8.1%, p = 0.011]-while no changes were observed in free testosterone [4.1%, p = 0.326]. Bodyweight, body composition, and energy intake were unchanged from pre- to post-test. Triiodothyronine (T3) [4.8%, p = 0.008], absolute RMR [3.0%, p = 0.010], relative RMR [2.6%, p = 0.013], and RMRratio [3.3%, p = 0.011] decreased, and cortisol levels increased [12.9%, p = 0.021], while no change were observed in the total testosterone:cortisol ratio [1.6%, p = 0.789] or the free testosterone:cortisol (fT:cor) ratio [3.2%, p = 0.556]. A subgroup analysis of the five participants with the largest increase in fT:cor ratio, revealed a greater improvement in functional threshold power (9.5 vs. 2.5%, p = 0.037), and higher relative RMR (0.6 vs. -4.2% p = 0.039, respectively). In conclusion, 4 weeks of intensified endurance interval training increased the athletes' aerobic performance and testosterone levels. However, negative changes in markers related to RED-S, such as a reduction in RMR and T3, and an increase in cortisol were observed. These results indicate the complexity involved, and that male athletes are at risk of developing clinical indications of RED-S even during a short 4-week endurance training mesocycle.