During the protocol the volunteers will sit in thermoneutral condition for 30 minutes, than they will sit in hot chamber (40 celsius and 40% relative humidity). Afterwards, the participants will walk on a treadmill in 5 km/hr and 4% incline for one hour. The participants will be connected to rectal thermistor which is considered the "gold standard" and to the new noninvasive sensor which is attached to the skin surface.