Colonic and tail-skin temperature responses of the rat at selected running speeds

Abstract

The relationship between work intensity and equilibrium body temperature at low and high running speeds in the rat was studied. After training to run for 60-90 min at speeds of 32-43 m/min on a level treadmill, 5 animals performed 3 runs at 10.8, 21.6, 32.4 and 42.6 m/min assigned in random order. In a 2nd experimental series, 6 animals ran at 16.2 and 32.4 m/min alternately every 30 min for 90 min. Experiments were performed at a room temperature of 22 .+-. 1.degree. C. Colonic (Tco) and tail-skin (Tts) temperatures were monitored continuously. Equilibrium Tco (mean .+-. SD) achieved in the last 30-45 min of exercise at 10.8, 21.6, 32.4 and 42.6 m/min were 39.0 .+-. 0.5, 39.2 .+-. 0.57, 39.5 .+-. 0.57 and 40.0 .+-. 0.55.degree. C, respectively. Mean Tco were significantly different between 42.6 m/min and the other speeds (P < 0.01), and between 32.4 and 10.8 m/min (P < 0.05). Using mean individual data, a proportional trend between colonic temperature and work load was observed in only 2 of the 5 animals. In the 2nd experimental series, mean Tco averaged over the last 15 min of each 30 min work period were not significantly different between the 2 speeds. The rat can achieve thermal balance during exercise, but a proportional relationship between the rise in internal temperature and work load was not reliably demonstrated.