Characterizing the Physiological Demands & Serum Cortisol Levels of Thru-Hiking the Continental Divide Trail

The popularity of thru-hiking is expanding within the outdoor recreation industry, drawing attention to the physiological demands of prolonged endurance activities in natural environments. This study examined the effects of a long-distance thru-hike on circadian rhythm regulation, body composition, and physical fitness parameters in two adult subjects who undertook the Continental Divide Trail in 2021. Serum cortisol concentrations were measured in the morning and evening at four time points: pre-hike, mid-hike, post-hike, and 16 weeks post-hike. Physical fitness testing included assessments of body composition, maximal oxygen uptake, and muscular endurance were conducted at pre-hike, post-hike, and 16 weeks post-hike. Both subjects demonstrated significant physiological adaptations, including changes in evening serum cortisol concentrations and alterations in adipose tissue and muscle mass. The female subject showed marked improvements in lower body muscular endurance and maximal oxygen uptake, while the male subject experienced reductions in muscle mass and muscular endurance, while maintaining aerobic capacity. These findings suggest that thru-hiking may influence endocrine function and physical fitness dependent on initial fitness status and individual physiological characteristics. This study highlights the need for further research to better characterize the health impacts of thru-hiking.