A snow cave is a bivouac shelter used in mountain climbing that is widely used as a shelter against the cold during winter. In the outdoors, wind velocity and air temperature have an influence on temperature change. It could stabilize body temperature if it can control the convection of ambient air. This paper could develop a theory focusing on the relation between physiological indexes and the protection against the cold while staying in a snow cave. For example, protection against the cold could be thermal insulation underwear, thermal insulation gloves, thermal insulation socks, a steam warmed temperature sheet and a rescue sheet. Measurement items were heart rate, blood pressure, rectal temperature, score of a subjective thermal sensation and the activity of the parasympathetic nervous system. It was clarified that the protection against the cold could be effective for the decrease of the physiological index. These field studies suggest that they would enable the adaptation in the adjustment range of the autonomic nervous system given these protections against the cold
