[Positive cross-adaptation between endurance physical training and general cold tolerance to acute cold exposure in rats].

This investigation suggested that a series of endurance physical training in rats could cause an improved cold tolerance in rats. The warm-acclimated control group was kept in a thermally neutral environment (25 +/- 1 degrees C). The trained group was subjected to forced physical training on a treadmill, exercising once 1 hour daily, and five times per week for the periods of 3 to 13 weeks. The cold-acclimated group was exposed to an ambient temperature of 5.0 +/- 0.5 degrees C for 12 weeks. Improved endurance physical fitness was suggested by a cardiac hypertrophy. The positive correlation was shown between the amount or intensity of training and the enhanced thermogenesis to acute cold exposure. However, no effect of endurance training was observed on the metabolic responses to noradrenaline and adrenaline. It was inferred that the acute cold exposure caused greater utilization of blood glucose in the trained rats than in the warm controls, but did not FFA in the latter. The increases in oxygen consumption and colonic temperature were caused by hexamethonium injection during cold exposure in the trained rats, but not in the warm and cold-acclimated rats. The increased metabolic rate to acute cold exposure was improved by the prolonged physical training. The development of greater metabolic rate during acute cold exposure in the trained rats was indicated to be associated with increased noradrenaline and adrenaline-independent non-shivering thermogenesises as well as enhanced resting metabolic rate at 25 degrees C ambient temperature.