12 healthy civilian volunteers will arrive to our lab and will undergo 4 experiment days: Recruitment day + VO2max test, 3 random days performing experiment protocol, dressed in uniforms: sitting in thermoneutral condition for one hour, afterwards they will walk on a treadmill in 5.5 km/h and 4% incline in hot chamber (40% celsius and 40% relative humidity) for 1.5 hours. Once connected to rectal thermistor and to the Double Sensor attached to the skin surface by sticker, once same as the day before with addition of cooling system of Icetron Technologies Ltd. worn on the wrist, and once connected to rectal thermistor and to the Double Sensor integrated into a helmet.