INTRODUCTION: Low energy availability (EA) may be detrimental to an athletes` health and performance [1], but the interaction between EA and altitude training adaptations warrants exploration. Therefore, the present study investigated EA during a 21-day period of normobaric "live high, train low" (LHTL) and examined whether athletes with positive hemoglobin mass (Hbmass) responses had different EA compared to the athletes with neutral / negative responses. METHODS: 10 female skiers completed a 21-day period (~18 h·day-1) of LHTL in normobaric hypoxia of ~2500 m while 11 female skiers formed a control group (CON) that lived and trained in normoxia. Hbmass was assessed using a carbon monoxide rebreathing method and fat-free body mass (FFM) from bioimpedance measurement within 2 days before starting a LHTL/CON period (PRE) and within a week after LHTL/CON period (POST). An athlete was classified as Hbmassresponder if Hbmass increased by >1.7% from PRE to POST based on the typical measurement error reported for the CO rebreathing method [2] and others were classified as Hbmass-non-responders. Energy intake (EI) was assessed using 3-day food logs, which were completed from the 10th to 12th day of the LHTL or CON period. Exercise energy expenditure (EEE) was assessed based on the duration and mean heart rate of the training sessions. Daily EA was calculated as: EA = (EI - EEE) / FFM. Differences between Hbmass-responders and non-responders were analyzed with a two-way ANOVA with group (LHTL, CON) and response (responders, non-responders) as between subject factors. RESULTS: LHTL increased Hbmass 3.3 ± 2.4% (7 responders, 3 non-responders) and CON 0.9 ± 2.3% (4 responders, 7 non-responders), but the main effect of group was not statistically significant (p = 0.38) showing no differences between the groups. Hbmass-responders had similar EEE (p = 0.72) but higher EI (p = 0.034) and EA (p = 0.008, Figure 1) than Hbmass-non responders in both LHTL and CON. A total of three athletes had an infection during the study (Figure 1). All three had low EA (< 30 kcal·kg FFM-1·d-1). CONCLUSIONS: Higher EA may support Hbmass adaptations and healthy training days during 21 days of LHTL as well as during 21 days of normal training at sea level. These findings highlight the importance of adequate dietary intake to optimize hematological adaptations to training and hypoxia.
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