Changes in systolic arterial pressure variability are associated with the decreased aerobic performance of rats subjected to physical exercise in the heat

• Published in: Journal of thermal biology Vol. 63; pp. 31 - 40
• Main Authors: Müller-Ribeiro, Flávia C., Wanner, Samuel P., Santos, Weslley H.M., Malheiros-Lima, Milene R., Fonseca, Ivana A.T., Coimbra, Cândido C., Pires, Washington
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.01.2017; Elsevier BV
• Subjects: Aerobic capacity; Aerobics; Animals; Autonomic nervous system; Autonomic Nervous System - physiology; Blood Pressure; Cardiovascular system; Carotid artery; Environmental conditions; Exercise; Fatigue; Heart Rate; Heat; Hot environment; Hot Temperature; Laboratory animals; Male; Parasympathetic activity; Physical Exertion - physiology; Physical training; Rats; Rats, Wistar; Rodents; Surgery; Sympathetic activity; Sympathovagal balance; Treadmill running; Sympathovagal balance; Fatigue; Sympathetic activity; Hot environment; Parasympathetic activity; Treadmill running
• ISSN: 0306-4565; 1879-0992
• DOI: 10.1016/j.jtherbio.2016.11.006

Enhanced cardiovascular strain is one of the factors that explains degraded aerobic capacity in hot environments. The cardiovascular system is regulated by the autonomic nervous system, whose activity can be indirectly evaluated by analyzing heart rate variability (HRV) and systolic arterial pressure (SAP) variability. However, no study has addressed whether HRV or SAP variability can predict aerobic performance during a single bout of exercise. Therefore, this study aimed to investigate whether there is an association between cardiovascular variability and performance in rats subjected to treadmill running at two ambient temperatures. In addition, this study investigated whether the heat-induced changes in cardiovascular variability and reductions in performance are associated with each other. Male Wistar rats were implanted with a catheter into their carotid artery for pulsatile blood pressure recordings. After recovery from surgery, the animals were subjected to incremental-speed exercise until they were fatigued under temperate (25°C) and hot (35°C) conditions. Impaired performance and exaggerated cardiovascular responses were observed in the hot relative to the temperate environment. Significant and negative correlations between most of the SAP variability components (standard deviation, variance, very low frequency [VLF], and low frequency [LF]) at the earlier stages of exercise and total exercise time were observed in both environmental conditions. Furthermore, the heat-induced changes in the sympathetic components of SAP variability (VLF and LF) were associated with heat-induced impairments in performance. Overall, the results indicate that SAP variability at the beginning of exercise predicts the acute performance of rats. Our findings also suggest that heat impairments in aerobic performance are associated with changes in cardiovascular autonomic control. •Running rats display augmented blood pressure in hot than in temperate environment.•Rats with lower performance exhibit exaggerated adrenergic activity during exercise.•Rats with higher performance exhibit lower blood pressure variability during exercise.•Increased blood pressure variability is related to impaired performance in the heat.•Blood pressure variability at the onset of exercise can predict rat's performance.