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

This study systematically reviewed the literature reporting the changes in rats’ core body temperature (TCORE) 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 TCORE 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 TCORE 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 TCORE (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 TCORE at the end of the exercise. In conclusion, rats subjected to treadmill running exhibit heterogeneous TCORE when fatigued or exhausted. Moreover, it is not possible to determine a narrow range of TCORE associated with exercise cessation in hyperthermic rats. Ambient temperature, initial TCORE, and physical performance-related variables are the best predictors of TCORE 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.本研究系统综述了报道大鼠核心体温（core body temperature, TCORE）变化的相关文献，这些变化由以递增速度或恒定速度进行跑台运动至疲劳或力竭所诱导。此外，本研究采用多元线性回归分析，以明确运动中断时达到的TCORE值的影响因素。本研究于2021年10月检索了EMBASE、PubMed、SPORTDiscus及Web of Science四个数据库，并于2022年8月更新了检索策略。本系统综述最终纳入72项研究，共计1538只大鼠。这些研究的实验条件存在显著异质性：例如，环境温度区间为5℃至40℃。各研究中大鼠终止运动时的TCORE值差异幅度超过8℃，最低值与最高值分别为34.9℃与43.4℃。多元线性回归分析结果显示，环境温度（p < 0.001）、初始TCORE（p < 0.001）、运动距离（p < 0.001，仅递增速度运动组）以及跑步速度与运动时长（p < 0.001，仅恒定速度运动组）均可显著解释运动结束时TCORE的变异情况。综上，进行跑台运动的大鼠在疲劳或力竭状态下的TCORE存在显著异质性。此外，无法确定高热状态下大鼠运动停止时对应的TCORE狭窄区间。环境温度、初始TCORE以及与运动表现相关的变量，是预测疲劳或力竭状态下TCORE的最佳指标。从更广泛的视角来看，本系统综述为未来开展大鼠运动体温调节相关研究的实验方法选择提供了有价值的参考依据。