Military Applications of Hypoxic Training for High-Altitude Operations


Medicine & Science in Sports & Exercise: September 2007 - Volume 39 - Issue 9 - pp 1625-1631
doi: 10.1249/mss.0b013e3180de49fe
BASIC SCIENCES: Symposium: Altitude/Hypoxic Training: Research-Based Evidence and Practical Application

Rapid deployment of unacclimatized soldiers to high mountainous environments causes debilitating effects on operational capabilities (physical work performance), and force health (altitude sickness). Most of these altitude-induced debilitations can be prevented or ameliorated by a wide range of physiological responses collectively referred to as altitude acclimatization. Acclimatization to a target altitude can be induced by slow progressive ascents or continuous sojourns at intermediate altitudes. However, this "altitude residency" requirement reduces their utilization in rapid response military missions that exploit the air mobility capability of modern military forces to quickly deploy to an area of operations on short notice. A more recent approach to induce altitude acclimatization is the use of daily intermittent hypoxic exposures (IHE) in lieu of continuous residence at high altitudes. IHE treatments consist of three elements: 1) IHE simulated altitude (inspired oxygen partial pressure: PIO2), 2) IHE session duration, and 3) total number of IHE sessions over the treatment period. This paper reviews and summarizes the results of 25 published IHE studies. This review finds that an IHE altitude ≥ 4000 m, and daily exposure duration of at least 1.5 h repeated over a week or more are required to have a high probability of developing altitude acclimatization. The efficacy of shorter duration (< 1.5 h) hypoxic exposures at ≥ 4000 m simulated altitudes, and longer exposures (> 4 h) at moderate altitudes (2500-3500 m) is not well documented. The predominate IHE-induced altitude acclimatization response appears to be increased arterial oxygen content through ventilatory acclimatization. Thus, IHE is a promising approach to provide the benefits of altitude acclimatization to low-altitude-based soldiers before their deployment to high mountainous regions.

U.S. Army Research Institute of Environmental Medicine, Natick, MA

Address for correspondence: Stephen R. Muza, Ph.D., Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA 02053; E-mail:

Submitted for publication November 2006.

Accepted for publication May 2007.

© 2007 American College of Sports Medicine