HUMAN RACIAL BESPONSES 



2 G to 3 C lowering of the critical temperature occurred in the 

 acclimatized. 



Le Blanc (1956) found a significantly decreased oxygen consump- 

 tion in cold acclimatized soldiers as compared with that of nonaccli- 

 matized controls when both were exposed to a series of standard 

 acute cold stresses. He suggested that acclimatization is associated 

 with a lowering of the body thermostat to more economical levels. 



Milan et al. (1961) studied antarctic sojourners who spent a 

 year at Little America V. The metabolic rates and the thermal res- 

 ponses of eight subjects (who served as their own controls), exposed 

 nude to 17 G air temperature were measured over the year. Mean 

 body and average skin and foot temperatures increased significantly 

 over the year, whilethere was a decrease in heat production to meet 

 the same thermal demands since shivering diminished. 



Davis et al. (1961) exposed six male white subjects nude to 

 13.5 G air temperature in a cold room 8 hours each day for 31 days 

 (except Sunday) in September and October. At the end of this period, 

 metabolism remained between 35% and 75% above basal values, but 

 shivering decreased. Skin temperatures were unchanged. 



In a similar experiment, Davis et al. (1961) exposed ten male 



white subjects to 11.8 G for 31 days in March. At the end of this 



o o 



period, rectal temperatures had decreased (37.2 Cto36.7 G) , skin 



temperatures were unchanged, and although metabolism was un- 

 changed, shivering decreased. These authors suggest thattheseare 

 indications of non-shivering thermogenesis. 



Adams et al. (1958) and Heberling et al. (1961) have demon- 

 strated that elevated skin temperature during cold stress may be a 

 result of an increase in physical fitness. 



Trends 



Although it is difficult at first glance to generalize about these 

 experiments investigating acclimatization and adaptation, there are 

 certain trends which are apparent: 



355 



