Association between the increase in brain temperature and physical performance at different exercise intensities and protocols in a temperate environment

Abstract

There is evidence that brain temperature (Tbrain) provides a more sensitive index than other core body temperatures in determining physical performance. However, no study has addressed whether the association between performance and increases in Tbrain in a temperate environment is dependent upon exercise intensity, and this was the primary aim of the present study. Adult male Wistar rats were subjected to constant exercise at three different speeds (18, 21, and 24 m/min) until the onset of volitional fatigue. Tbrain was continuously measured by a thermistor inserted through a brain guide cannula. Exercise induced a speed-dependent increase in Tbrain, with the fastest speed associated with a higher rate of Tbrain increase. Rats subjected to constant exercise had similar Tbrain values at the time of fatigue, although a pronounced individual variability was observed (38.7-41.7°C). There were negative correlations between the rate of Tbrain increase and performance for all speeds that were studied. These results indicate that performance during constant exercise is negatively associated with the increase in Tbrain, particularly with its rate of increase. We then investigated how an incremental-speed protocol affected the association between the increase in Tbrain and performance. At volitional fatigue, Tbrain was lower during incremental exercise compared with the Tbrain resulting from constant exercise (39.3±0.3 vs 40.3±0.1°C; P<0.05), and no association between the rate of Tbrain increase and performance was observed. These findings suggest that the influence of Tbrain on performance under temperate conditions is dependent on exercise protocol.

Increased brain l‐arginine availability facilitates cutaneous heat loss induced by running exercise

“…Elevated T core levels and high rates of heat storage are associated with the interruption of prolonged exercise in mammals . It has been suggested that hyperthermia may reduce the drive to exercise and hasten sensations of fatigue, thus protecting the brain from thermal damage.…”

“…Elevated T core levels and high rates of heat storage are associated with the interruption of prolonged exercise in mammals. [9][10][11][12] It has been suggested that hyperthermia may reduce the drive to exercise and hasten sensations of fatigue, 9,35,36 thus protecting the brain from thermal damage. However, contrary to expectations, pharmacological manipulations that attenuate hyperthermia do not extend the time to fatigue in running rats.…”

“…The ability to tolerate prolonged exertion in temperate and warm environments is largely limited by hyperthermia. Both an elevated core body temperature ( T core ) and high rates of heat storage have been associated with fatigue . There is experimental evidence demonstrating that nitrergic neurotransmission modulates thermoregulation.…”

“…Both an elevated core body temperature (T core ) and high rates of heat storage have been associated with fatigue. [9][10][11][12] There is experimental evidence demonstrating that nitrergic neurotransmission modulates thermoregulation. Intracerebroventricular (i.c.v.)…”

Pre-exercise exposure to the treadmill setup changes the cardiovascular and thermoregulatory responses induced by subsequent treadmill running in rats

“…Other experimenters subject rats to exercise immediately after placing them on the treadmill. 8,[16][17][18][19][20] Although both handling and treadmill exposure may represent psychological stressors to rats, no study has compared the physical performance and exerciseinduced physiological responses of rats exposed to these two experimental approaches (i.e., with or CONTACT Samuel P. Wanner samuelwanner@eeffto.ufmg.br Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, Pampulha.…”