Changes

==Mechanisms==

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

* 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.

** 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.

** Recent studies indicate that IHE stimulates NO (Nitric Oxide) production, with the excess stored in the vascular walls. This improves blood pressure.

* Research<ref name="jack"/> using highly trained runners showed no running improvement with IHE. However, this study used IHE for 4 weeks and had O₂ saturation values of 89.9, 86.3, 85.9, and 81.4 for each week. The value of IHE is dependent upon the O₂ saturation levels, with little effect until values under 89%<ref name="HTI"/>. 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.

* 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. <ref name="acu"/>

* 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

==Intermittent Hypoxic Exposure and Diseases==