Por que alguns ratos são mais sensíveis ao comprometimento do desempenho aeróbico induzido pelo ambiente quente do que outros? Um estudo de regressão linear múltipla

Abstract

Aerobic (prolonged) physical performance is markedly impaired in hot compared to temperate conditions. However, the reduction in performance caused by a hot environment is not homogenous among rats of the same strain. This study aimed to characterize the variability in the heat-induced reduction in performance and identify factors that could predict this variability. Seventy-eight adult Wistar rats (66 males and 12 females) were subjected to two incremental-speed treadmill runs interspersed by at least 48 hours: one in a hot environment [ambient temperature = 24°C] and the other in a temperate environment (32°C). The order of these trials was randomized and counter-balanced. Rats were exercised until they were fatigued, and their body core (TCORE) and skin temperatures were measured at regular intervals. The distance traveled was taken as the index of physical performance. Multiple linear regression analyses were conducted to identify factors predicting the heat-induced changes in performance. As expected, the distance traveled was reduced by 39% in rats exercised at 32°C compared to 24°C. A marked inter-individual variability was observed in the heat-induced changes in distance traveled (coefficient of variation = 88.6%). Using multivariable analysis, we reported that the distance traveled at 24°C, biological sex, and the heat effect on the change in TCORE from the beginning until the 10th minute of exercise were the variables that better predicted the heat-induced changes in performance. In conclusion, we confirmed the different sensitivity among rats to the heat-induced decrements in aerobic performance, which is explained by thermoregulatory and non-thermoregulatory factors.