Physiological reactions to different vertical (head-foot) air temperature differences

Abstract

Six healthy male subjects were exposed to different vertical air temperature differences between the upper and lower parts of the body for 90 min, wearing light clothing. The lower part of the body was exposed to an air temperature of 25°C and the upper part of the body to air temperatures of 15, 20, 25, 30 or 35°C.

The preferred air temperature was different from those for uniform experimental conditions found by other investigators. The thermal sensations on the upper part of the body and the whole body were similar, and those on the lower part of the body were almost constant under each condition. From the relationship between thermal sensation and mean skin temperature, subjects may feel thermal neutrality at a slightly lower mean skin temperature, when the lower part of the body is at a comfortable temperature, than when both upper and lower parts of the body are exposed to the same temperature.

The lower part of the body was exposed to thermally neutral condition and the skin temperatures of the lower extremities were then affected by the upper-body air temperatures. The skin temperatures on the toe and instep increased with increasing upper air temperatures. The skin temperatures on the instep after 90 min were higher than those on the leg and thigh at upper air temperature of 25, 30 and 35°C.

Index terms:

• Skin temperature
• rectal temperature
• tympanic temperature
• metabolic rate
• thermal sensation
• comfortable air temperature.