Author(s): MCKAY, A., WALKER, A., BURKE, L., Institution: AUSTRALIAN CATHOLIC UNIVERSITY, Country: AUSTRALIA, Abstract-ID: 1780

INTRODUCTION:
Sustained energy deficits in athletes can have negative health and performance outcomes. Two models of assessing energy status exist; (1) Energy Balance (EB), which subtracts energy intake (EI) from total daily energy expenditure (TDEE), and (2) Energy Availability (EA), which is defined as EI minus exercise energy expenditure (EEE) relative to fat free mass (FFM). The aim of this study was to quantify EB and EA in group of elite rowers during an altitude training camp.
METHODS:
Forty-five Tier 4-5 male (n=17, 26±2 y, 96±7 kg, 5.9±0.7 L/min) and female (n=28 27±3 y, 78±8 kg, 4.2±0.7 L/min) rowers completed the study. Using a prospective, observational design, EA and EB were measured for 6-days in the middle of the camp. Athletes had ad libitum access to food, with meals provided in a dining hall and additional snacks available throughout the day. An observer report method was used to discreetly measure EI. Training was prescribed by national team coaches and was primarily undertaken on rowing or cycling ergometers, where session duration, power output and heart rate were recorded. Individually assessed (via metabolic measures) gross efficiency outcomes were then employed to calculate EEE. All other training was estimated using metabolic equivalent of task scores. Doubly labelled water was used to measure total daily energy expenditure (TDEE) and physical activity levels (PAL) were established by dividing TDEE by predicted resting metabolic rate (RMR). Body composition (fat mass (FM) and FFM) were assessed via DXA at the start and end of the camp. Data are mean [95% confidence interval], where t-tests and Pearson correlations were used.
RESULTS:
The average EA of athletes over 6-days was 49.7 [47.0-52.4] kcal/kg/FFM/day, which occurred despite the high energy flux (EI: 5235 [4963-5508] kcal/day; EEE: 1894 [1778-2010] kcal/day). The corresponding EB was +184 [-36 -+405] kcal/day which was calculated based on TDEEs of 5051 [4749-5352] kcal/day. The resulting PAL was 2.7 [2.6-2.9]. Activity energy expenditure accounted for more than 50% of TDEE, with ~38% of that attributed to EEE. While sex differences for EI, EEE and TDEE were apparent (all p<0.001), no differences in EA (p=0.761) or EB (p=0.472) occurred. Strong correlations between change in FM and EA (r=0.57, p<0.001) but not EB (r=0.25, p=0.102) were noted.
CONCLUSION:
To our knowledge this is the largest field-based assessment of EA and EB in elite athletes using gold standard assessments, including a physiological, individualised approach to EEE quantification, prospective weighed dietary intake and doubly labelled water. Our data demonstrate the ability of elite rowers to sustain good energy status in the face of incredibly high energy flux, with 31 (69%) athletes reporting a PAL >2.5, which is has been proposed as the metabolic ceiling of sustained energy expenditure. Only EA, not EB correlated with changes in FM, demonstrating the utility of well conducted EA assessments.