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Am J Physiol Regul Integr Comp Physiol (January 4, 2007). doi:10.1152/ajpregu.00622.2006
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Submitted on August 31, 2006
Accepted on December 29, 2006

Intermittent hypobaric hypoxia exposure does not cause sustained alterations in autonomic control of blood pressure in young athletes

Qi Fu1, Nathan E. Townsend2, S. Michelle Shiller3, Emily R. Martini4, Kazunobu Okazaki4, Shigeki Shibata4, Martin J Truijens5, Ferran A. Rodriguez6, Christopher J. Gore2, James Stray-Gundersen7, and Benjamin D. Levine7*

1 The University of Texas Southwestern Medical Center at Dallas, Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, Dallas, Texas, United States
2 Australian Institute of Sport, Australia
3 Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas , Dallas, Texas, United States; The University of North Texas Health Science Center , Fort Worth, Texas, United States
4 Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, Dallas, Texas, United States
5 Faculty of Human Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
6 Institut Nacional d'Educacio Fisica de Catalunya, Universitat de Barcelona, Barcelona, Spain; The University of Texas Southwestern Medical at Dallas, Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, Dallas, Texas, United States
7 Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, Dallas, Texas, United States; The University of Texas Southwestern Medical Center at Dallas , Dallas, Texas, United States

* To whom correspondence should be addressed. E-mail: benjaminlevine{at}texashealth.org.

Intermittent hypoxia (IH) refers to the discontinuous use of hypoxia to reproduce some key features of altitude acclimatization. It is commonly used in athletes to improve their performance. Variations of IH are also used as a model for sleep apnea causing sustained sympathoexcitation and hypertension in animals, raising concerns over the safety of this model. We tested the hypothesis that chronic IH exposure at rest alters autonomic control of arterial pressure in healthy trained individuals. Twenty-two young athletes (11 males, 11 females) were randomly assigned to either hypobaric hypoxia (simulated altitude of 4,000-5,500m) or normoxia (500m) in a double blind and placebo controlled design. Both groups rested in a hypobaric chamber 3 h/d and 5 d/wk for 4 wk. Resting hemodynamics including heart rate (HR), blood pressure (BP), cardiac output (Qc, C2H2 rebreathing), stroke volume (SV=Qc/HR), total peripheral resistance (TPR=mean BP/Qc) were measured, dynamic cardiovascular regulation was assessed by spectral and transfer function analysis of cardiovascular variability, cardiac-vagal baroreflex function was evaluated by Valsalva maneuvers, twice before and three days after the last chamber exposure in the sitting position. We found that there were no differences in HR, BP, Qc, SV, TPR, cardiovascular variability, or cardiac-vagal baroreflex function between groups at any time. These results suggest that 4 wk of intermittent hypobaric hypoxia exposure does not cause sustained alterations in autonomic control of blood pressure in young athletes. In contrast to animal studies, we found no secondary evidence for sustained physiologically significant sympathoexcitation in this model.




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F. A. Rodriguez, M. J. Truijens, N. E. Townsend, J. Stray-Gundersen, C. J. Gore, and B. D. Levine
Performance of runners and swimmers after four weeks of intermittent hypobaric hypoxic exposure plus sea level training
J Appl Physiol, November 1, 2007; 103(5): 1523 - 1535.
[Abstract] [Full Text] [PDF]


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