Cold resistance estimated on the basis of fetal hemoglobin changes during acute general cooling

In order to find a criterion for human cold resistance and adaptability we studied the reaction of hematological indices to acute general cooling of the whole organism (12 degrees C, 1 h) in 60 male volunteers 19-25 years old living in Norilsk (69 degrees N) for about 2 1/2 years. The first group of subjects comprised of cold adapted individuals whose professional activity was associated with 4-5 hrs daily work outdoor in cold environment. The volunteers of the second group regularly worked indoor and are considered a priori cold unadapted. Our results indicate that fetal hemoglobin (HbF) concentration shows the most remarkable reaction to acute cooling in comparison with other parameters studied (erythrocyte count, hematocrit, total hemoglobin level). Cold exposure of unadapted young males was accompanied by a marked increase of HbF concentration in venous blood (from 1.27 +/- 0.13% to 2.04 +/- 0.02%, p less than 0.01), whereas the same procedure in the adapted subjects was followed by practically unchanged HbF levels. These findings lead us to the conclusion, that the change of the HbF level under acute general cooling can be considered a satisfactory criterion of human cold resistance.