title: Changes in systolic arterial pressure variability are associated with the decreased aerobic performance of rats subjected to physical exercise in the heat.
abstract: 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.
authors.affiliation: Exercise Physiology Laboratory, Department of Physical Education, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Flávia C
authors.initials: FC
authors.lastname: Müller-Ribeiro
authors.affiliation: Exercise Physiology Laboratory, Department of Physical Education, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Samuel P
authors.initials: SP
authors.lastname: Wanner
authors.affiliation: Exercise Physiology Laboratory, Department of Physical Education, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Weslley H M
authors.initials: WH
authors.lastname: Santos
authors.affiliation: Exercise Physiology Laboratory, Department of Physical Education, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Milene R
authors.initials: MR
authors.lastname: Malheiros-Lima
authors.affiliation: Exercise Physiology Laboratory, Department of Physical Education, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Ivana A T
authors.initials: IA
authors.lastname: Fonseca
authors.affiliation: Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Cândido C
authors.initials: CC
authors.lastname: Coimbra
authors.affiliation: Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil; Department of Physical Education, Institute of Life Sciences, Universidade Federal de Juiz de Fora, Governador Valadares, MG, Brazil. Electronic address: washpires@gmail.com.
authors.forename: Washington
authors.initials: W
authors.lastname: Pires
mesh_terms: D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology; D001794:Blood Pressure; D006339:Heart Rate; D006358:Hot Temperature; D008297:Male; D005082:Physical Exertion / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
keywords: Fatigue; Hot environment; Parasympathetic activity; Sympathetic activity; Sympathovagal balance; Treadmill running