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

Qi Fu, Nathan E. Townsend, S. Michelle Shiller, Emily R. Martini, Kazunobu Okazaki, Shigeki Shibata, Martin J. Truijens, Ferran A. Rodríguez, Christopher J. Gore, James Stray-Gundersen, Benjamin D Levine

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

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

Original languageEnglish (US)
Pages (from-to)R1977-R1984
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume292
Issue number5
DOIs
StatePublished - May 2007

Keywords

  • Altitude
  • Arterial pressure
  • Autonomic nervous system
  • Baroreflexes
  • Cardiovascular variability
  • Hemodynamics

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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