on the chest back upper arm lower arm thigh and calf the humidity sensors consisted of a capacitance type relative humidity sensor and a thermocouple to measure the sensor 39 s temperature ti skin wetness is a specific measure of skin moisture and is defined as the fraction of skin 39 s surface that must be covered with water to account for the observed evaporation rate gagge a p 34 a new physiological variable associated with sensible and insensible perspiration 34 american journal of physiology vol 20 2 pp 277 287 1987 it is expressed as a fraction from 0 to 1 or as a percentage the local skin wetness wi can be calculated from the local skin temperature tski relative humidity rhi measured next to the skin under clothing and the ambient temperature ta and relative humidity rha as follows wi rhi ps ti rha ps ta pa tski rha ps ta where ps ti ps ta and ps tski are the saturation vapor pressure of water at temperatures ti ta and tski respectively the average skin wetness under clothing is the area weighted mean of the local wetness values photo optical devices were applied to the ear lobe to measure the subjects 39 heart rate oxygen consumption was measured at the appropriate periods with a mask and an open flow measuring system.