Total Energy Expenditure And Intake During A 162 Km Mountain Ultramarathon

Mountain ultramarathons impose unique and challenging physical demands on runners. Although past research has described the total energy expenditure (TEE) during these events, less is known regarding ad libitum nutrient and fluid budgets. PURPOSE: To measure and compare TEE and ad libitum intake during a 162 km mountain ultramarathon in runners of varied mass. METHODS: Two experienced ultra-runners (R1, 45 yrs, 74.4 kg; R2, 31 yrs, 59.2 kg) completed a mountainous ultramarathon (162 km, 7500 m of vertical gain). Each runner received an oral dose of doubly labeled water (2H218O; DLW) 30 h before the event. Urine and nude body mass were collected at 24 h pre, pre, and post-event for the calculation of total body water (TBW), TEE, and water turnover (rH2O). Self-reported food and fluid intake were recorded at crew-accessible aid stations, and total energy intake (TEI) was determined from salvaged food wrappers. RESULTS: Race finish time including pre- and post-sample collection segments was 33.6 and 33.8 h for R1 and R2, respectively. TEE during that period was 66.1 MJ (15,800 kcals, 6.6 x BMR) and 66.8 MJ (15,969 kcal, 7.5 x BMR) for R1 and R2, respectively. TEI was 34.5 MJ (8253 kcals) for R1 and 29 MJ (6931 kcals) for R2, representing 52% and 43% of TEE. CHO intake represented 80% and 77% of caloric intake, with intake rates of 50.4 and 40.4 g/h for R1 and R2. Fluid budgets from rH2O were calculated at 14.6 kg, 20% of initial TBW (R1) and 15.5 kg, 26% of initial TBW (R2). Body mass loss was 1.5 and 2.2 kg, representing 2.0 and 3.7% of initial body mass for R1 and R2, respectively. CONCLUSION: These data help accurately illustrate the demanding energy requirements inherent in running a 162 km mountain ultramarathon and provide insight into runners' fueling and hydration strategies. Recognition of precise measures of TEE can provide insights into appropriate fuel and fluid management practices for athletes competing in similar events.