Aerobic performance in rats subjected to incremental-speed running exercise: A multiple regression analysis study emphasizing thermoregulation-related variables.

Single-variable analyses have limited ability to explain complex phenomena such as the regulation of prolonged physical (aerobic) performance. Our study aimed to identify predictors of performance in rats subjected to incremental-speed running exercise. Notably, most variables assessed were associated with rats' thermoregulation. We extracted data from 355 records obtained in 216 adult Wistar rats. Hierarchical multiple linear regression analyses were conducted to identify the predictive power of eight variables. The distance traveled, a performance index, was the dependent variable. The independent variables included body mass, biological sex, body core temperature (T_CORE) measurement site, and the following thermoregulation-related variables: ambient temperature (T_AMB), initial T_CORE, exercise-induced change in T_CORE (ΔT_CORE), ΔT_CORE from 0 to 10 min (ΔT_CORE 0-10; when T_CORE increase is fastest), and heat loss index (HLI). This analysis with eight variables revealed an adjusted R² of 0.495; T_AMB, ΔT_CORE, body mass, and ΔT_CORE 0-10 had the highest predictive powers (β values: -0.700, 0.463, -0.353, and -0.130, respectively). Additional analyses consisted of separate regressions for each T_CORE index measured: abdominal (T_ABD), brain (T_BRAIN), and colonic (T_COL) temperature. These analyses yielded adjusted R² values of 0.608 (T_ABD), 0.550 (T_BRAIN), and 0.437 (T_COL). Again, the distance traveled was primarily predicted by body mass and thermoregulation-related variables (T_AMB, ΔT_CORE, and ΔT_CORE 0-10). Among these four variables, ΔT_CORE was the only one with a positive β value (directly predicted performance), while the others had negative values. Collectively, these findings advance our understanding of performance regulation in rats, especially regarding the role of thermoregulation-related variables.