Author(s): HAYASHI, S., TANAKA, K., Institution: FUKUYAMA CITY UNIVERSITY, Country: JAPAN, Abstract-ID: 1998

INTRODUCTION:
Mount Fuji, the highest peak in Japan, attracts numerous climbers each year. Despite its popularity, hypothermia-related incidents are periodically reported and occasionally require emergency rescue. Such cases may be linked to inadequate understanding of rapidly changing weather conditions and insufficient preparation. Although mountaineering is a high-intensity activity that typically elevates core body temperature, ambient temperature decreases progressively with increasing altitude, particularly above 3,000 m. Sudden weather changes and strong winds may further accelerate heat loss. While prior studies have examined exercise intensity and environmental factors during Mount Fuji ascents, limited data are available regarding rectal temperature responses during actual climbing. This pilot study therefore aimed to evaluate changes in rectal temperature during ascent of Mount Fuji under clear weather conditions.
METHODS:
Three healthy Japanese men participated. Baseline measurements were obtained at the fifth station, approximately 2,300 m above sea level, after which participants ascended to the summit via the Gotemba route. Rest periods were scheduled every 40 minutes, and measurements were conducted at each station. Variables included heart rate, rating of perceived exertion, subjective thermal sensation, peripheral oxygen saturation, and rectal temperature. Ambient temperature, humidity, wet-bulb globe temperature, and altitude were recorded concurrently. After summit assessment, participants rested for one hour, descended to the fifth station, and underwent final measurements.
RESULTS:
Heart rate and perceived exertion increased after ascent began, whereas heart rate declined from approximately the seventh station onward. Peripheral oxygen saturation decreased progressively with altitude and reached its lowest value at the summit. Rectal temperature increased until approximately the seventh station, corresponding to elevations above 3,000 m, and then declined during the final phase of ascent. After descent, physiological variables except perceived exertion returned to near-baseline levels.
CONCLUSION:
High-altitude mountaineering imposes substantial physiological stress and reduces oxygen availability. Above 3,000 m, slower climbing speed and lower ambient temperature may have contributed to the observed reduction in rectal temperature. Although no marked hypothermia was observed under clear conditions, insufficient clothing during continued activity may predispose climbers to rapid core temperature decline in adverse weather. These preliminary findings should be interpreted cautiously because of the small sample size. Larger studies under diverse environmental conditions are warranted to clarify thermoregulatory responses and support strategies to prevent mountaineering-related accidents.