Long-distance \"thru-hiking\" has extraordinary physical demands and has become increasingly popular. This report describes a man (55 y) who thru-hiked the Pacific Crest Trail in 2021 and was at risk of developing the relative energy deficiency in sport (RED-S) syndrome. Hiking distance was 3767 km over 128 d. Eighty-eight days (69%) were full days of hiking, covering 38±8 km/d (mean±SD) in 7.9±1.6 h/d. Exercise energy expenditure above rest (heart rate vs indirect calorimetry regression method) was 2834±1518 kcal/d, total energy expenditure was 5702±1323 kcal/d, and energy intake was 4141 kcal/d. Body mass decreased by 9%, and fat mass (dual-energy X-ray absorptiometry) decreased by 46%. Energy availability (energy intake minus exercise energy expenditure) was 19.3 kcal/d/kg fat-free mass, indicating low energy availability (defined as <30 kcal/d/kg). Dual-energy X-ray absorptiometry-measured spine bone mineral density (BMD) decreased by 8.6%, with little to no decrease in total hip (-1.0%) and femoral neck (-1.5%) BMD. Total cholesterol, low-density lipoprotein cholesterol, and triglycerides increased by 24, 39, and 57%, respectively. Within 8 mo after the hike, BMD and serum lipids nearly or fully returned to baseline. No changes in high-density lipoprotein cholesterol, glycemia, or blood pressure were observed. According to guidelines, these observations are consistent with a moderate risk of RED-S, and a medical evaluation and treatment plan are advisable in order to avoid clinical manifestations (eg, stress fractures, anemia, psychological disturbances). To minimize RED-S risk, it may be prudent for thru-hikers to optimize energy availability by moderating daily hiking distances and/or increasing food intake.

Relative Energy Deficiency in Sport (RED-S) defines insufficient calorie intake for the physiological and athletic functions of the athlete, and accordingly deterioration in the musculoskeletal, hormonal, cardiovascular and immune systems. Herein, we present a 42-year-old female long-distance runner with multiple pelvic stress fractures who didn\'t complete her prescribed treatment program and wanted to keep running despite being aware of the associated pain and risks. The Goldman dilemma refers to the unsettling reality that a significant number of professional athletes may contemplate sacrificing their lives in order to achieve Olympic glory. This disregard for the numerous challenges stemming from an obsession with success is equally applicable to the amateur athlete depicted in this case. Our patient\'s fractures were examined in relation to RED-S and managed through conservative treatment methods. The RED-S and Goldman dilemma should be kept in mind not only in professional but also in semi-professional, and amateur athletes.

Research into relative energy deficiency in sport (RED-S) has increased substantially over recent years given the impact on athletes\' health and performance. Most studies have considered sports that place emphasis on the aesthetics, endurance, or weight-restriction. Fewer studies exist in team sports. Netball is a team sport yet to be explored despite players potentially being at risk of RED-S given the high training volumes, sporting culture, internal and external pressures, and small network of coaches and medical professionals. A qualitative case study was used to explore the perspective of athletes, coaches, and medical professionals on RED-S.
Semi-structured interviews were conducted with 13 players, 4 coaches and 4 medical professionals affiliated to a Super League club. Interviews were recorded and transcribed verbatim. The data was analysed using thematic analysis.
Five main themes were identified in this study. Awareness of RED-S amongst athletes and coaches was generally inadequate whereas medical professionals had some awareness of RED-S. Some athletes used contraception to reduce discomfort/pain during menstruation whilst others expressed concerns around long-term contraceptive use and previous menstrual cycle disturbance. Sporting demands, individual and contextual factors, and a preoccupation with body image were associated with nutritional restriction, whilst appearance was a source of internal and external pressure. External pressures also extended to coaches, assessments/feedback, social media, and commentary. Strategies suggested to reduce the risk of RED-S included \"hard hitting cases\", multidisciplinary team involvement, and support from the governing body.
The findings of this study provide insight into factors potentially associated with the risk of RED-S from an athletes, coaches, and medical professional perspective. This insight can be used to increase overall awareness of RED-S in key stakeholders as well as improve the recognition for the pressures netball athletes face that might alter the level of risk.

OBJECTIVE: To highlight energy availability status, resting metabolic rate measures, dietary protein intake, and testosterone concentration in 4 elite male track cycling athletes (mean [SD]: age: 20.8 [1.5] y, body mass: 76.3 [3.6] kg, height: 181.8 [2.9] cm).
METHODS: A cross-sectional observation included measures of energy availability (energy intake minus exercise energy expenditure, divided by fat-free mass), resting metabolic rate from indirect calorimetry, dietary protein intake from food records, blood analysis to assess sex hormone status, and performance markers.
RESULTS: Midrange testosterone (16.9-19.8 nmol/L), lowered resting metabolic rate ratio (0.76-0.98), varied luteinizing hormone (4-10 U/L), and suboptimal energy availability (26-41 kcal/kg fat-free mass/d, range) were observed in the male track cyclists. Protein intakes ranged from 2.0 g to 2.8 g protein/kg/d.
CONCLUSIONS: The current cohort may have within-day energy deficiency, putting them in a catabolic state.

The purpose of this case series was to evaluate the presence of low Energy Availability (EA) and its impact on components of Relative Energy Deficiency in Sport (RED-S) in a population of female collegiate runners. Seven female NCAA Division I athletes (age: 22.3 ± 1.5 yrs; height: 169.7 ± 5.7 cm; weight: 58.3 ± 4.1 kg) were tracked from August until February, covering the beginning (Pre XC), end (Post XC) of their competitive cross country season, and beginning of the following track season (Pre Track). The athletes were assessed for female athlete triad (Triad) risk, energy availability, body composition, resting metabolic rate (RMR), nutritional intake, and blood markers (including vitamin D, ferritin, and triiodothyronine (T3)). From Pre XC to Post XC there were no significant differences in body mass, fat free mass or body fat percentage. At Pre XC, mean EA was 31.6 ± 13.3 kcal/kg FFM∙d-1. From Post XC to Pre Track, there was a significant increase in body mass (59.1 ± 5.1 to 60.6 ± 5.7 kg, p<0.001,d=0.27). From Post XC to Pre Track, there was a significant increase in RMR (1466 ± 123.6 to 1614.6 ± 89.1 kcal·d-1, p<0.001,d=2.6). For 25(OH) vitamin D, there was a significant reduction from Pre XC to Post XC (44.1 ± 10.6 vs 39.5 ± 12.2 ng·mL-1, p=0.047,d=-0.4), and a significant increase from Post XC to Pre Track (39.5 ± 12.2 vs. 48.1 ± 10.4 ng·mL-1, p=0.014,d=0.75). For ferritin, there was a trend towards a decrease from Pre XC to Post XC (24.2 ± 13.2 vs. 15.7 ± 8.8 ng·mL-1, p=0.07, d=-0.75), as well as a trend toward an increase from Post XC to Pre Track (15.7 ± 8.8 vs. 34.1 ± 18.0 ng·mL-1, p=0.08, d=1.3). No differences in T3 were observed across time points. Average Triad risk score was 2.3 ± 1.4. Notably, 5 of 7 athletes met criteria for moderate risk. Despite many athletes meeting criteria for low EA and having elevated Triad risk assessment scores, most were able to maintain body mass and RMR. One athlete suffered severe performance decline and a reduced RMR. Surprisingly, she was the only athlete above the recommended value for ferritin. Following increased nutritional intake and reduced training volume, her performance and RMR recovered. Changes in body mass and body composition were not indicative of the presence of other concerns associated with RED-S. This exploratory work serves as a guide for future, larger studies for tracking athletes, using RMR and nutritional biomarkers to assess RED-S.