Simulate hypoxic training by breath holding/regulation

Question

Is it possible to physically simulate hypoxic training by doing periodic breath holds or breath regulation during aerobic activity?

Ideally, it ought to be done in a hypobaric/hypoxic chamber whilst strapped to some monitors. But short of that, I can think of two ways -

1. While running, every few minutes, I can try to hold my breath for a couple of steps initially and gradually increase it to 8-10 steps
2. if I normally run say 6 steps per inhalation+exhalation cycle and I try to increase it to 7 and further on.

What I would like to understand is

1. if it will work?
2. the risks involved, and how to mitigate them (e.g. a pulse oximeter on a finger to monitor?)

I considered posting this question on the physical fitness SE, but did it here instead considering that I would prefer an answer by someone trained in the medical sciences.

In general, based on past work (ref: 1, 2, 3, and 4) it seems that intermittent hypoxic training is indeed beneficial. But most "professional" work (both researchers and athletes) in the area uses hypoxic chambers - which is not practical for the average internet user.

What is less clear is if breath control is an adequate method of simulating hypoxic training. The only reliable references (the runnbetternow website and an NIH publication by a yoga center) I could find aren't exactly by medical professionals. FWIW, these references are in favor of the method. The question is if medical practitioners agree.

The end goal here is to prepare for mountain activities. As it is not practical to move one's permanent base to a mountain top, one would like to be able to somehow simulate high altitude training whilst still living at sea level. Of course, this will be in addition to (not in lieu of) actually periodically training at altitude.

Answer 1

The approach you describe most likely will not work, and could be detrimental to your training.

The main benefit of training at altitude is that the body will adapt to the lower concentration of oxygen by stimulating the production of erythropoietin which in turn causes the body to produce more red blood cells.

What you are describing is a very limited version of intermittent hypoxic training (IHT). In subelite athletes, this has been shown to have some effect, however it was 60 minutes of training using a protocol of 3-5 minutes of hypoxia followed by the same amount of time of normoxia (normal breathing). (Also cited here.)

In a study of male subelite competitive cyclists and triathletes, athletes were exposed to intermittent hypoxia (artificial brief intermittent LHTL) for 15 days over 3 weeks for 60 min per day with either 3 or 5 min periods of hypoxia followed by the same duration in normoxia. Cycling performance improved during incremental step exercise, including increases of 4.7% ± 3.1% in peak aerobic power, 4.4% ± 3.0% in lactate profile power, and 6.5% ± 5.3% in heart rate profile power compared to control measured 3 days post-intervention.35 Fourteen days after treatment, differences between the hypoxia groups were unclear, suggesting that intermittent hypoxia training should be timed for competitive events to take place within a few days following treatment. In a similar study, performance did not improve among elite athletes,36 suggesting that artificial brief intermittent LHTL should be considered mainly by subelite athletes.

The most common method of attempting to achieve this is a training mask, which restricts air flow. Most studies (like this one) reject the claim that it helps by actually simulating altitude, but they do note that it helps train the respiratory muscles and may help improve lung usage.

The short period that you describe really won't have enough of an impact on the body to stimulate altitude related changes in blood and plasma.

Answer 2

Since there is a good answer already I'll just add my two cents from my understanding of physiology: Hypoventilation has two effects during exercise:

1. Less available oxygen in your lungs and a somewhat less amount of oxygen in the blood that comes out of your lungs, which is not as big a difference as you might expect because hemoglobin is incredibly efficient at sucking up all available oxygen. Under stress conditions (heat, acid metabolites and CO2 all inhibit the binding of oxygen to hemoglobin) this sucking up is somewhat dampened but if the gradient is large enough large quantities of oxygen are still easily captured in the lungs.
2. A large increase of CO2 in your blood, which in turn stimulates your breathing reflex, making it near impossible to force yourself to breathe less. This effect would be much larger.

Furthermore, to be successful at high altitude survival there is one key aspect that needs to be there, and I'm not sure if it can be trained: Hyperventilation is essential to get enough oxygen into your blood under hypoxic conditions. Most people don't have a strong enough breathing reflex though to breath more when oxygen is low and CO2 is normal or low. It's not natural to hyperventilate, and not very healthy either. Maybe it can be trained at sea level to compensate for the stress that hyperventilation causes on your body?

Interestingly, the people of Tibetan descent that lived in the Himalaya evolved a protecting mechanism against the increase of red blood cells during long stays at high altitudes. Other peoples that live at high altitude, for example those that live in the Andes lack this protection and their blood thickens up to a point where it causes serious health problems.

Dehydration is another serious threat at high altitude: hyperventilation makes you lose plenty of water through your breath. And brain swelling is also a nasty complication of stays at very high altitudes...