Core body temperatures of rats subjected to treadmill exercise to fatigue or exhaustion: The journal <i>Temperature toolbox</i>

This study systematically reviewed the literature reporting the changes in rats’ core body temperature (T_CORE) induced by either incremental- or constant-speed running to fatigue or exhaustion. In addition, multiple linear regression analyses were used to determine the factors contributing to the T_CORE values attained when exercise was interrupted. Four databases (EMBASE, PubMed, SPORTDiscus, and Web of Science) were searched in October 2021, and this search was updated in August 2022. Seventy-two studies (<i>n</i> = 1,538 rats) were included in the systematic review. These studies described heterogeneous experimental conditions; for example, the ambient temperature ranged from 5 to 40°C. The rats quit exercising with T_CORE values varying more than 8°C among studies, with the lowest and highest values corresponding to 34.9°C and 43.4°C, respectively. Multiple linear regression analyses indicated that the ambient temperature (<i>p</i> &lt; 0.001), initial T_CORE (<i>p</i> &lt; 0.001), distance traveled (<i>p</i> &lt; 0.001; only incremental exercises), and running speed and duration (<i>p</i> &lt; 0.001; only constant exercises) contributed significantly to explaining the variance in the T_CORE at the end of the exercise. In conclusion, rats subjected to treadmill running exhibit heterogeneous T_CORE when fatigued or exhausted. Moreover, it is not possible to determine a narrow range of T_CORE associated with exercise cessation in hyperthermic rats. Ambient temperature, initial T_CORE, and physical performance-related variables are the best predictors of T_CORE at fatigue or exhaustion. From a broader perspective, this systematic review provides relevant information for selecting appropriate methods in future studies designed to investigate exercise thermoregulation in rats.