Tadakatsu Ohnaka

Thermal reaction and manual performance during cold exposure while wearing cold-protective clothing

Abstract Subjects were exposed in a climatic chamber for 60min to air temperature at — 5, —15 and — 20°C wearing cold-protective clothing with cotton working gloves. Subjects were asked to perform a 15 s counting task using a manual counter as fast as possible with the right hand, at approximately 15-min intervals during cold exposure. Skin and rectal temperatures were measured. On cold exposure, skin temperatures and body temperatures dropped gradually; after 1 hour most sites were colder, especially hand and finger temperatures. Finger temperatures decreased gradually with time, and steeply at the lower air temperatures, being temporarily raised by the counting task performed and possibly by cold-induced vasodilatation. By contrast, the gradual decline in hand temperatures showed no such transient changes. The decline in task performance with time was greater the lower the air temperature. The performance at -20°C decreased significantly with each further 15min exposure in comparison with the values bef...

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

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 low...

The effects of different vertical air temperatures on mental performance.

Mental performance (one-digit-addition test) under conditions of different vertical air temperatures (upper body vs. lower body) was studied in relation to psychological and physiological responses. Six healthy male subjects wearing light clothing were exposed to different vertical air temperatures for 105 min. The lower part of the body was exposed to an air temperature of 30 degrees C in all cases; the upper part of the body was exposed to temperatures of 15 degrees C, 20 degrees C, 30 degrees C and 35 degrees C. The performance in the one-digit-addition test decreased with increased upper air temperature, and upper air temperatures higher or lower than 25 degrees C resulted in increased discomfort. There was little difference between performance at the onset (5 min after exposure) and conclusion (90 min after exposure) at 15 degrees C and 20 degrees C upper air temperatures (UAT). The performance at 90 min, however, declined in comparison with the original value at 25 degrees C, 30 degrees C and 35 degrees C UAT. Mildly uncomfortable ambient conditions where upper air temperatures were cool and lower air temperatures were warm improved performance; however, at 35 degrees C, UAT performances worsened as the subjects felt uncomfortably hot.