Abstract
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 (n = 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 (p < 0.001), initial T(CORE) (p < 0.001), distance traveled (p < 0.001; only incremental exercises), and running speed and duration (p < 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.