The aim of this study was to provide information on energy availability (EA), macronutrient intake, nutritional periodization practices, and nutrition knowledge in young female cross-country skiers. A total of 19 skiers filled in weighted food and training logs before and during a training camp. Nutrition knowledge was assessed via a validated questionnaire. EA was optimal in 11% of athletes at home (mean 33.7 ± 9.6 kcal·kgFFM⁻¹·d⁻¹) and in 42% at camp (mean 40.3 ± 17.3 kcal·kgFFM⁻¹·d⁻¹). Most athletes (74%) failed to meet recommendations for carbohydrate intake at home (mean 5.0 ± 1.2 g·kg⁻¹·d⁻¹) and 63% failed to do so at camp (mean 7.1 ± 1.6 g·kg⁻¹·d⁻¹). The lower threshold of the pre-exercise carbohydrate recommendations was met by 58% and 89% of athletes while percentages were 26% and 89% within 1 h after exercise, at home and at camp, respectively. None of the athletes met the recommendations within 4 h after exercise. Nutrition knowledge was associated with EA at home (r = 0.52, p = 0.023), and with daily carbohydrate intake at home (r = 0.62, p = 0.005) and at camp (r = 0.52, p = 0.023). Carbohydrate intake within 1 and 4 h post-exercise at home was associated with better nutrition knowledge (r = 0.65, p = 0.003; r = 0.53, p = 0.019, respectively). In conclusion, young female cross-county skiers had difficulties meeting recommendations for optimal EA and carbohydrate intake. Better nutrition knowledge may help young athletes to meet these recommendations.

Study aim : The aim of this study was to evaluate if young female skiers meet their energy and macronutrient requirements, and how energy availability (EA) and macronutrient intake affects their performance during an intensive training camp. Material and methods : 19 female cross-country skiers (age 16.7 ± 0.7) filled in 48-hour food and training logs during a 5-day training camp. Fasting concentrations of hemoglobin, leptin, triiodothyronine (T3), insulin, insulin-like growth factor 1 (IGF-1), and glucose were measured before (PRE) and after (POST) the camp. Blood lactate (LA), heart rate (HR) and rating of perceived exertion (RPE) from a submaximal treadmill running test, jump height from counter movement jump (CMJ), and power from a reactive jump test (RJ) were also measured PRE and POST. Results : Mean EA was 40.3 ± 17.3 kcal · kgFFM ^–1 · d ^–1 . 58% of the participants had suboptimal EA, 37% had low EA, and 53% had suboptimal carbohydrate intake. HR, HR/RPE ratio, LA/RPE ratio, CMJ, hemoglobin, leptin, T3, and insulin decreased from PRE to POST. RPE and glucose increased from PRE to POST. EA during the camp correlated with changes in LA (r = 0.54, p = 0.018), LA/RPE (r = 0.65, p = 0.003), and RJ (r = 0.47, p = 0.043). Conclusions : Many athletes had difficulties in meeting their energy and carbohydrate requirements during a training camp. Furthermore, sufficient EA may help to avoid overreaching and to maintain performance during an intensive training period.

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 (similar to 18 h day(-1)) of LHTLH in normobaric hypoxia of similar to 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 (H-bmass) 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 similar to 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.

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. 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 (VO_2max), 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. 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 VO_2max (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 VO_2max 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). 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.

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.

Purpose : To investigate if elite endurance athletes periodized their body mass (BM) and composition from preparation (T ₁ ) to specific preparation period (T ₂ ) and if changes in BM and body composition were associated with improved endurance performance. Methods : Fifty-two elite endurance athletes participated in this study. Thirteen cross-country skiers, 7 biathletes, and 3 Nordic Combined athletes formed a group of skiers (16 men and 7 women), and 5 endurance runners, 22 orienteers, and 2 triathletes formed a group of runners (17 men and 12 women). Anthropometric (dual-energy X-ray absorptiometry) and performance (sport-specific incremental treadmill test) measurements were completed in T ₁ and T ₂ . Results : No changes in BM or body composition were detected from T ₁ to T ₂ except for lean mass (LM), which increased in only runners ( P = .03). Peak running speed (V _peak ; P < .001) and relative peak oxygen uptake ( P = .04) increased from T ₁ to T ₂ regardless of the sport or sex. Decreased body fat mass and percentage were associated with increased V _peak ( r = −.41, P = .002; r = −.45, P < .001) and relative peak oxygen uptake ( r = −.31, P = .03; r = −.32, P = .02). Changes in LM were positively associated with changes in V _peak in female skiers ( r = .80, P = .03), while almost all the female runners increased both LM and V _peak . Conclusions : Elite endurance athletes did not systematically periodize their BM from T ₁ to T ₂ . Decreases in body fat mass and percentage may be beneficial for endurance performance. Since increases in LM were associated with improved endurance performance in female athletes, body-composition manipulations should not lead to a decrease in LM.