Temperature regulation during treadmill exercise in the rat

The response of colonic and tail-skin temperatures to treadmill exercise was assessed in female Sprague-Dawley rats using incremental and single-stage exercise protocols to investigate the relationship between deep body temperature and work rate. O2 uptake (VO2) was measured by flow-through technique to evaluate the exercise intensity. Experiments were performed in ambient temperatures below (22-25 degrees C) and above (33-35 degrees C) the thermoneutral zone of the rat. During graded incremental exercise there was a linear relationship between colonic temperature (Tco) and VO2 in both the cooler and warmer ambient temperatures. However, Tco and tail-skin temperature (Tsk) at comparable work rates in the cooler and warmer environments were 40.22 +/- 0.59, 34.84 +/- 1.10 degrees C and 42.04 +/- 0.57, 38.39 +/- 1.54 degrees C, indicating that the rise in Tco was unrelated to the severity of exercise. During single-stage exercise the rats were able to achieve thermal equilibrium but only at low work rates and in the cool environment (22-25 degrees C). There were no significant differences in Tco at the first three levels of single-stage exercise (stage 1, 39.63 +/- 0.34 degrees C; stage 2, 39.67 +/- 0.49 degrees C; stage 3, 39.75 +/- 0.50 degrees C) despite significant differences in VO2 (stage 1, 4.3 +/- 0.7 ml X min-1 X 100 g-1; stage 2, 5.3 +/- 0.6 ml X min X 100 g-1; stage 3, 7.6 +/- 1.2 ml X min-1 X 100 g-1). This demonstrates that there was no relationship between the level of Tco maintained during exercise and the work intensity.(ABSTRACT TRUNCATED AT 250 WORDS)