| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 Air Force Research Laboratory, Directed Energy Bioeffects Division; 2 Veridian Engineering at Air Force Research Laboratory, Directed Energy Bioeffects Division, Brooks Air Force Base, 78235; and 3 Department of Biology, Trinity University, San Antonio, Texas 78212
We examined whether fatigue during exertional heat stress occurred at a critical internal temperature independent of the initial temperature at the start of exercise. Microwaves (2.1 GHz; 100 mW/cm2) were used to rapidly (3-8 min) heat rats before treadmill exercise to exhaustion. In a repeated-measures design, food-restricted male Sprague-Dawley rats (n = 11) were preheated to three levels (low, medium, and high). In addition, two sham exposures, Sham 1 and Sham 2, were administered at the beginning and end of the study, respectively. At the initiation of exercise, hypothalamic (Thyp) and rectal (Trec) temperatures ranged from 39.0°C to 42.8°C (Thyp) and 42.1°C (Trec). The treadmill speed was 17 m/min (8° grade), and the ambient temperature during exercise was 35°C. Each treatment was separated by 3 wk. Run time to exhaustion was significantly reduced after preheating. There was a significant negative correlation between run time and initial Thyp and Trec (r = 0.73 and 0.74, respectively). The temperatures at exhaustion were not significantly different across treatments, with a range of 41.9-42.2°C (Thyp) and 42.2-42.5°C (Trec). There were no significant differences in run time in the sham runs administered at the start and end of the investigation. No rats died as a result of exposure to any of the treatments, and body weight the day after each treatment was unaffected. These results support the concept that a critical temperature exists that limits exercise in the heat.
brain; electromagnetic fields; hypothalamus; microwaves; thermoregulation; treadmill
This article has been cited by other articles:
|
|
 |
|
  L. Nybo Hyperthermia and fatigue J Appl Physiol, March 1, 2008; 104(3): 871 - 878. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Hasegawa, M. F. Piacentini, S. Sarre, Y. Michotte, T. Ishiwata, and R. Meeusen Influence of brain catecholamines on the development of fatigue in exercising rats in the heat J. Physiol., January 1, 2008; 586(1): 141 - 149. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R.J. Maughan, S.M. Shirreffs, and P. Watson Exercise, Heat, Hydration and the Brain J. Am. Coll. Nutr., October 1, 2007; 26(suppl_5): 604S - 612S. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. H. R. Leite, A. C. R. Lacerda, U. Marubayashi, and C. C. Coimbra Central angiotensin AT1-receptor blockade affects thermoregulation and running performance in rats Am J Physiol Regulatory Integrative Comp Physiol, September 1, 2006; 291(3): R603 - R607. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. M. Thomas, S. S. Cheung, G. C. Elder, and G. G. Sleivert Voluntary muscle activation is impaired by core temperature rather than local muscle temperature J Appl Physiol, April 1, 2006; 100(4): 1361 - 1369. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. A. Grahn, V. H. Cao, and H. C. Heller Heat extraction through the palm of one hand improves aerobic exercise endurance in a hot environment J Appl Physiol, September 1, 2005; 99(3): 972 - 978. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Hasegawa, T. Ishiwata, T. Saito, T. Yazawa, Y. Aihara, and R. Meeusen Inhibition of the preoptic area and anterior hypothalamus by tetrodotoxin alters thermoregulatory functions in exercising rats J Appl Physiol, April 1, 2005; 98(4): 1458 - 1462. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. G Martin, F. E Marino, J. Rattey, D. Kay, and J. Cannon Reduced voluntary activation of human skeletal muscle during shortening and lengthening contractions in whole body hyperthermia Exp Physiol, March 1, 2005; 90(2): 225 - 236. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. G. Rodrigues, N. R. V. Lima, C. C. Coimbra, and U. Marubayashi Intracerebroventricular physostigmine facilitates heat loss mechanisms in running rats J Appl Physiol, July 1, 2004; 97(1): 333 - 338. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. A. Arngrimsson, D. S. Petitt, M. G. Stueck, D. K. Jorgensen, and K. J. Cureton Cooling vest worn during active warm-up improves 5-km run performance in the heat J Appl Physiol, May 1, 2004; 96(5): 1867 - 1874. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Nybo, N. H Secher, and B. Nielsen Inadequate heat release from the human brain during prolonged exercise with hyperthermia J. Physiol., December 1, 2002; 545(2): 697 - 704. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Nybo and B. Nielsen Perceived exertion is associated with an altered brain activity during exercise with progressive hyperthermia J Appl Physiol, November 1, 2001; 91(5): 2017 - 2023. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Nybo and B. Nielsen Hyperthermia and central fatigue during prolonged exercise in humans J Appl Physiol, September 1, 2001; 91(3): 1055 - 1060. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
