Introduction: Insufficient dietary energy to maintain normal physiological function results in a state of ‘low energy availability’ (LEA). LEA is believed to be the aetiological factor underpinning endocrine, metabolic and physiological dysregulations often observed in athletes(1-4), given laboratory-based controlled studies in humans show a causal role between LEA and endocrine dysregulations. However, these studies inflict a homogenous pattern of LEA that may not be ecologically valid. Endurance athletes have been identified as at risk of suffering from the consequences of prolonged LEA due to persistently high daily exercise energy expenditure (EEE)(5). However, to date there is no study characterising the relationship between the EEE and energy availability (EA) of these athletes in typical training conditions. The aim of this study was to characterise daily EEE and dietary energy intake (EI), to assess the EA of a cohort of elite male road-cyclists during seven consecutive days of pre-season training. We hypothesised that EA would be inversely related to EEE. Methods: Ten male, elite cyclists (22 ± 8 years, 75.1 ± 8.5 kg body mass [BM], 65.4 ± 7.4 kg estimated fat free mass [FFM], 1.84 ± .05 m, 5.27 ± 0.25 W•kg-1 20 min Mean Maximal Power) were assessed during 7 consecutive days of pre-season training. Dietary intake was assessed using the remote-food photography method and EI calculated from macronutrient content of foods (NutriticsTM, Ireland). EEE was estimated from cycling crank-based power-meter data, and by using METS for other exercise types. FFM was estimated from BM and team dual X-ray absorptiometry fat % records. Daily EA was calculated as (EI – net EEE)/FFM. The relationship between EA & EEE, EA & EI and EEE & EI were determined using linear regressions. Results: High variation in daily EA was observed, ranging from -21.9 to 76.0 kcal•kg FFM-1•day-1. Mean daily EA was 19.5 ± 22.0 kcal•kg FFM-1•day-1, reaching ‘Low’ EA (<30 kcal•kg FFM-1•day-1) in 71% (5/7) of training days. Daily EEE averaged 38.4 ± 25.9 (98.9 % of EEE from cycling) and EI 57.9 ± 13.3 kcal•kg FFM-1•day-1, with ranges of 0.0 to 99.8 and 28.5 to 95.0 kcal•kg FFM-1•day-1 respectively. We show a very large, negative, linear relationship between EA and EEE (R2 = .735; 95% CL: -1.155 & -.862; P < 0.001) but a small, positive, linear relationship between EEE and EI (R2 = .278; 95% CL: .166 & .378; P <.001) (Figure 1). Conclusions: Large fluctuations in daily EEE appear to dictate heterogenous EA values observed during seven consecutive days of pre-season training in elite male cyclists. The majority of the sessions were undertaken in what is typically deemed LEA. EI increased slightly with EEE but did not fully compensate for it. Periods of homogeneous LEA induced in laboratory-based research do not replicate the EA patterns observed in the field in this population.