Energy expenditure and physiological markers during a city mountain hike in the heat: A case study.

This article focuses on assessing physical activity exercise energy expenditure (PAEE) during a strenuous hike in hot conditions using direct oxygen uptake measurement (cardiopulmonary exercise testing, CPET), heart rate (HR) monitoring, and metabolic equivalent (MET) values from the 2011 Compendium of Physical Activities. In a case study of a 38-year-old male hiker, CPET measured a total PAEE of 1342 kcal over 124 minutes, revealing a two-fold difference between ascending and descending energy costs, while HR-based estimates overreported PAEE by approximately 34%. MET-based estimates from published tables provided reasonable approximations of PAEE but did not precisely reflect individual workload or environmental factors such as heat stress. The study also documented thermoregulatory responses, including a core body temperature peak of 39.2°C and a sweat rate of 1300 mL/hour, emphasizing the importance of hydration strategies to limit body weight loss to 1–2% during hiking in hot environments. The findings suggest that MET tables may offer more accurate PAEE estimates than HR monitoring alone in steep, hot hiking conditions.