The effect of training on the norepinephrine response at rest and during exercise in 5 degrees and 20 degrees C...

Eleven males were examined at rest and during submaximal exercise in 5 degrees C and 20 degrees C environments to determine if the norepinephrine (NE) and other physiological responses in the cold would be altered by eight weeks of training. Blood samples were obtained at the end of 15 minutes of rest and submaximal exercise, and were assayed for NE. Pretraining resting NE levels in the 5 degrees C condition were significantly higher than those found in the 20 degrees C environment (684 +/- 89 vs 491 +/- 48 pg/ml). A significant training effect reduced resting NE levels in the 5 degrees C (502 +/- 77 pg/ml) but not the 20 degrees C (392 +/- 45 pg/ml) condition. Pre and posttraining exercise NE levels were elevated above resting in both the 5 degrees C (1477 +/- 136 vs 1559 +/- 208) and the 20 degrees C environments (1623 +/- 176 pg/ml vs 1444 +/- 224 pg/ml), but were not significantly different between conditions. Skin temperatures were significantly lower, and resting blood pressure was significantly higher in the 5 degrees C condition. These data suggest that both cold and exercise act as stimulators of NE release, but an additive effect on NE of cold and exercise does not occur. The resting NE levels pre and posttraining in the 5 degrees C condition suggest that a cross tolerance to cold stress was present.