Study Summary: Build more muscle with less oxygen

A study showed how muscles grew 4 to 6 times faster when air had only 16% oxygen. Normally, air has 21% oxygen. The study was published in 2010 in International journal of sports physiology and performance. See also what does resistance training do to the muscles.

7 male students trained biceps and triceps for 6 weeks under normal conditions (normoxia). 7 other students did the same in an oxygen-depleted room (hypoxia). 

Trained arm increased by about 8% in hypoxia. Untrained arm didn't and trained arm in normoxia increased a little.

The arm's maximum strength increased the most in the hypoxia group.

Oxygen depletion causes the body to produce more lactic acid. The acid stimulates testes and pituitary to produce more growth hormones and testosterone. 

Oxygen depletion increases free radicals and this in turn increases the body's anabolic processes.

In 2009, a study was published in Medicine and science in sports and exercise. This study showed how oxygen shortage also increase muscle mass and strength. 

The 12 healthy men were aged around 30 and regularly did weight training. During test they did 5 sets of bench presses and 5 sets of leg presses once under normal conditions and once in an oxygen depleted room. 

Oxygen depleted room made the subjects produce more lactic acid and growth hormone, but it didn't affect cortisol, IGF-1 and testosterone levels.

Oxygen depletion may also lead to faster weight loss. Stimulatory hormones (adrenalin and noradrenalin) force fat cells to release their contents into the blood.

Conclusion: Resistance exercise in acute systemic hypoxia caused greater accumulation of lactate, and greater response in growth hormone, adrenalin, and nor-adrenalin to a bout of resistance exercise.Hypoxia is a potent factor for the enhancements of anabolic hormone response to resistance exercise.

Oxygen depletion might cause a person to lose consciousness. This should be taken into account to avoid dangerous situations during training.