Objective.—Accurate reports of energy expenditure (EE) during prolonged mountaineering activity are sparse. The purpose of this study was to estimate EE during a winter ultraendurance climbing race and individual mountaineering activities in Mont Blanc, France.

Methods.—Seven days before the race, resting metabolic rate (RMR) and maximal oxygen consumption (Vo_2max) were measured in 10 experienced male climbers (30.0 ± 0.9 years). Three days before (reference period) and during the race, heart rate (HR) was recorded for estimation of total daily EE (TDEE), and the type and duration of all activities were collected through questionnaires. Total DEE was calculated by adding DEE during sleep (DEE sleep), sedentary (DEE sedentary), and during exercise (DEE exercise). Daily energy expenditure during exercise was determined through assumption of the rectilinear relationship between heart rate (HR) and Vo₂. Anthropometric measurements were performed 7 days before, just before, and immediately after the race.

Results.—Total time of the race averaged approximately 29 hours and 29 minutes, including 11 hours and 24 minutes in the hut, plus 18 hours and 5 minutes dedicated to climbing. During the race, TDEE was 43.6 ± 1.2 MJ·d⁻¹. Energy expenditures for cross-country skiing and alpine climbing were similar (57.3 ± 2.1 kJ·min⁻¹ and 54.0 ± 2.9 kJ·min⁻¹, respectively). An energy deficit of 33.5 ± 2.3 MJ resulted after the race, with a mean weight loss of 1.52 ± 0.31 kg (P < .001).

Conclusions.—Experienced climbers expended a high level of energy during a winter ultraendurance alpine climbing race at moderate altitude under high degrees of difficulty and risk exposure. These results provide comparative data on the energy cost of the main mountaineering activities during a race: cross-country skiing and alpine climbing.