Energy Expenditure and Intensity Levels During a 6170-m Summit in the Karakoram Mountains

Objective Although the majority of high altitude studies have used doubly labeled water to assess energy expenditure (EE), minimal research has examined variation in intensity levels while participating in such an expedition. The purpose of this study was to use ambulatory monitoring technology to assess EE and time spent in moderate (3.0–6.0 METS), vigorous (6.0–9.0 METS), and very vigorous (>9.0 METS) intensities during an expedition to summit a 6170-m peak in Northern Pakistan. Methods Twelve men and 2 women were studied. Their EE was determined from galvanic skin response, heat flux, and biaxial accelerometry using a multisensor armband. Lake Louise Scores for altitude illness assessment were obtained each morning. Results Average daily total EE and number of steps taken was 4173 ± 848 kcal/d (range, 3332 to 4838 kcal/d) and 26,232 ± 7210 steps/d (range, 11,788 to 34,979 steps/d), respectively. On average, subjects spent approximately 7.7 h/d performing physical activity (>3.0 METS). Of this, subjects spent 399 ± 107, 61 ± 77, and 3 ± 10 min/d at moderate, vigorous, and very vigorous intensity levels, respectively, corresponding to 88%, 11%, and 1% of total physical activity time. During summit day, subjects climbed at an intensity equivalent to approximately 42% of their high altitude predicted maximal oxygen consumption at 5100 m). Conclusions During a high altitude expedition, subjects predominantly exercise at a moderate intensity, with limited time spent at higher intensity levels. Use of accelerometer-based technology may provide more cost-effective and logistically easier means of assessing EE in extreme environments.