The Science of Intermittent Hypoxic Exposure

Use of Intermittent Hypoxic Training (IHT) is relatively new in the west, but the USSR (and later CIS) has been researching and using IHT since the 1930's. Usage includes sports, altitude acclimatization, and treatment of clinical disorders, including chronic lung diseases, bronchial asthma, hypertension, diabetes mellitus, Parkinson’s disease, emotional disorders, and even radiation toxicity.

1 Mechanisms

There appear to be three mechanisms underlying the effects of IHT: regulation of respiration, mitochondrial respiration, and free-radical production.

• The regulation of respiration results in increased sensitivity of breathing rate to altitude, improved gas exchange in the lungs and changes to the autonomic nervous system.
• Improvements in mitochondrial respiration results in optimized use of oxygen in energy production.
• Exposure to both low and normal oxygen levels improves the body's antioxidant defense.

The research shows that there is wide individual variation in the response to IHT and altitude. This variation exists in both humans and animals, and appears to be due to mechanisms beyond simple iron insufficiency.

2 Research from the USSR

• Expose subjects to 15,000 feet for 1 hour per day over several days for 7 to 11 sessions showed increased blood O₂ saturation compared with initial exposure and the benefits were detectable for up to 4 weeks.
• Exposure of 30 min to 3 hours every 2 to 3 days for 9 exposures increased hemoglobin by 12% and red blood cells by 22%
• Exposure of 3x (6 min low O2, 4 min normal air) per day for 14 days increased breathing volume at altitude by ~50%. Partial pressure of O₂ started at 50 mmHg (20,000 ft) dropping to 35 mmHg (28,000 ft). Several studies have shown similar results.
• 5x (15 min 11% O₂ + 15 min recovery) for 14 day produced changes to the metabolic pathways that optimize the use of oxygen.
• Studies in rats suggest that continuous exposure to altitude reduces anti-oxidant defenses, but IHT improves them.
• Other studies in rats indicate that IHT changes the ratio of fat to protein burning in favor of fats by 80%.
• A study of workers that cleaned up after Chernobyl nuclear reactor explosion showed that they had higher levels of oxidant stress where higher than normal. Exposing the workers to IHT of 3x (5 min 7-8% [28,000+ ft] O₂ with 5 min normal air) for 14 days significantly reduced the oxidant stress.
• Studies have shown IHT reduces the oxidant stress associated with bronchial asthma. (There were large variations in individual response, and more research is needed.)
• Recent studies indicate that IHT stimulates NO (Nitric Oxide) production, with the excess stored in the vascular walls. This improves blood pressure.
• Research indicates that there is a very wide variability in the response to altitude (IHT or other) and tolerance of extreme hypoxia. Future research may provide methods of overcoming the lack of response in some individuals.

3 Western Research

• Research using highly trained runners showed no running improvement with IHT. However, this study used IHT for 4 weeks and had O₂ saturation values of 89.9, 86.3, 85.9, and 81.4 for each week. The value of IHT is dependent upon the O₂ saturation levels, with little effect until values under 89%. The athletes in the study therefore only received significant hypoxia for about one week. The athletes were given 5 min hypoxic, 5 min normal for 70 minutes total for five days per week, 4 weeks total.
• A similar research study showed a significant improvement in 3K running performance. This study used 90 minutes of IHT (5 hypoxic:5 normal) for 15 days over a three week period, using 13,000 feet at the start to 19,000 feet at the end.
• A study looking at Hypoxia EPO, a hormone that stimulates red blood cell production showed a ~50% increase in EPO from 4 hours of IHT or 2 hours of continuous hypoxia, but no response from 5 minutes or 1 hour. The IHT was a simulated altitude of 18,000 ft
• Subjects exposed hypoxia in a hypobaric chamber showed elevated EPO levels after 114 min at 9,000 feet and or after 84 minutes at 12,000 feet. EPO levels continued to rise with longer exposure.
• Research using the AltoLab system showed a significant improvement in sprint speed. The study used 6 min hypoxia (10,000 to 18,000 ft) with 4 min recovery for an hour a day for 15 days. The study shown a tiny improvement in blood parameters (hemoglobin/hematocrit) normally associated with altitude training.
• IHT increased lung force in asthmatic and non-asthmatic athletes. There was no deterioration in asthma status from the trial, and half of the asthmatics reported a reduction in the need for medication. The trial used 15 sessions over three weeks, with each session being 5 min hypoxia followed by 5 min normal air, repeated for 60 minutes. The hypoxia was equivalent to 22,500 ft. Other studies have reported a similar improvement in asthma, with reduced attacks, reduced severity of attacks and reduced need for medication.

4 See Also

• Altitude Training
• Comparison of Altitude Training Systems
• Book Review – Altitude Training and Athletic Performance
• Intermittent Hypoxic Training
• AltoLab