Hyperthermia in running sled dogs.

Hyperthermia, as measured by increase in rectal temperature, was studied in a group of 22 adult mongrel sled dogs that had been selectively bred for high-speed (up to 33 km/h) races 16-50 km in distance. Under normal working conditions, rectal temperature in the sled dogs increased significantly during initial 15-20 min of run (gathered gallop) after which temperature usually stabilized or decreased slightly. Amount of increase in rectal temperature was correlated directly with ambient temperature but not with speed or distance. Significant differences in degree of hyperthermia were found among dogs but these differences were not correlated with such factors as sex, size, coat color, weight, or genetic history. Training was found to significantly diminish amount of increase in rectal temperature during work. Data from the present study were compared to those of other laboratory investigations and relationships of heat storage and radiative surface area to body weight are discussed.