Thermal responses to cold wind of thermoneutral and cooled subjects

The effects of initial thermal state on thermoregulatory responses to cold (-10 degrees C) in a 0.2 (still air), 1.0, and 5.0 m . s(-1) wind speed wer e studied. Eight young male subjects were first preconditioned in thermoneu tral ( + 20 degrees C, TN) or cool (-5 degrees C, CO) environment for 60 mi n. After preconditioning the subjects were exposed to wind at -10 degrees C in a standing position, facing the wind, for 30 min. Precooling decreased mean skin temperature ((T) over bar(sk)) by 4.0 (SEM 0.1)degrees C (P < 0.0 01) and increased heat flux by 57 (SEM 2) W . m(-2) (P < 0.001) in comparis on to TN. Cooling rate of (T) over bar(sk) was faster (P < 0.001) in TN tha n in CO at every wind speed. Even so, (T) over bar(sk) ended up at a lower level in CO (P < 0.001-0.01) than in TN at every wind speed. Local skin tem peratures of hand, finger, foot and toe were significantly lower in CO than in TN at the end of all exposures to wind. Heat flux from the skin was 8% higher (NS) in TN at 5.0 m s(-1) wind speed in comparison to CO. A 5.0 m s( -1) wind speed increased oxygen consumption significantly(P < 0.001) in bot h CO and TN in comparison to still air. At 5.0 m s(-1) wind speed the gener al thermal sensation was the same (cold) in both TN and CO, despite the hig her (T) over bar(sk) in TN. In conclusion, (T) over bar(sk) decreased more rapidly in TN, probably due to rapid skin vasoconstriction and redistributi on of circulation to the central body. Probably for the same reason, dry he at loss from the skin was at nearly the same level in both TN and CO. Altho ugh the initial thermal state did not affect the amount of heat loss, it si gnificantly affected the peripheral temperatures and thermal sensations and should therefore be taken into consideration in the prediction of thermoph ysiological responses to wind.