Total Energy Expenditure and Intake During a 161-km Mountain Ultramarathon

High total energy expenditure (TEE) and rate of water turnover (rH₂O) using doubly labeled water (²H₂¹⁸O) have been reported during single-stage and multistage ultraendurance events. At the 161-km distance, less is known about the interaction of TEE, rH₂O, and ad libitum energy/fluid intake. This is especially true during the postrace recovery window. Purpose: To measure TEE, rH₂O, and ad libitum energy/fluid intake during a 161-km ultramarathon while extending the TEE and rH₂O measurement window to a 7-day postrace period. Methods: Doubly labeled water was used to monitor TEE and rH₂O in 2 male ultrarunners (R1, R2) during a 161-km ultramarathon. Self-reported energy/fluid intake was recorded at crew-accessible aid stations. Results: Both runners completed the race in 32.8 hours, and TEE over this period was 65.8 MJ (6.5 × basal metabolic rate [BMR], 15,723 kcal, 11,225 kcal·24 h⁻¹) in R1 and 66.5 MJ (7.4 ×BMR, 15,888 kcal, 11,293 kcal·24 h⁻¹) in R2. Race energy intake for both runners approximated 50% of TEE, with reported fluid consumption of 21.8 L and 15.7 L for R1 and R2, respectively. rH₂O during the race was 14.6 L in R1 and 15.5 L in R2. During the 7-day postrace period, total TEE and rH₂O were 94.7 MJ (1.9 ×BMR, 22,634 kcal, 3245 kcal·d⁻¹) and 41.8 L for R1 and 80.0 MJ (1.8 ×BMR, 19,116 kcal, 2721 kcal·d⁻¹) and 24.0 L for R2, respectively. Conclusion: These data illustrate the expected nutrient and fluid budgets for ultramarathons and describe the challenge of restoring acute negative energy balance following these events.