Physiological conflict in humans: fatigue vs. cold discomfort.

Six male human subjects were placed in a situation of physiological conflict, fatigue vs. cold discomfort. Dressed in swim suits and shoes they walked at 3 km X h-1 on a treadmill placed in a climatic chamber. The slope of the treadmill was varied from 0 to 24% and the ambient temperature (Ta) from 25 to 5 degrees C. The subjects could choose Ta when slope was imposed or the converse. They rated pleasure and displeasure of Ta and exercise. Deep body temperature and heart rate were monitored. The results show that the subjects adjusted their behavior to maintain approximatively steady deep body temperature and to limit heart rate below 120 beats X min-1. The physiological compromise was thus correlated to the drive for maximal pleasure-minimal displeasure in the two sensory dimensions fatigue and discomfort.