Hypoxia is defined as an inefficient oxygen supply in the blood. When the human body is exposed to hypoxic environments, such as high altitudes, it struggles to produce the amounts of energy required to function.
Living and/or training at high altitudes is believed by many to enhance the efficiency of the body’s respiratory, cardiovascular and oxygen utilization. The state of hypoxia deprives the body of oxygen, the primary source of energy for our cells, and can trigger the onset of several physiological adaptations that could improve athletic performance. However while the fundamental theory is simple, results from studies are not unanimously positive and when present, performance enhancements ranged from about 2-3 percent after several weeks of solid training.
Might sound like small potatoes, but that’s a margin many elite athletes are after, and altitude training has been used for decades to enhance performance at sea level and also to prepare for competition at altitude.
Your body at altitude
When your body senses it is not receiving the amount of oxygen it is accustomed to, it begins to produce more red blood cells, which carry oxygen to your muscles. Your kidneys release a hormone called erythropoietin, which stimulates the production of red blood cells. The increased oxygen transportation from the red blood cells means your body will optimize the amount of available oxygen. The increase of red blood cells helps improve your VO2 max, which is the maximum amount of oxygen your body can obtain and use during intense exercise.
Acclimation to high altitudes theoretically improves the delivery of oxygen to the muscles, which means better performance and faster recovery. But the question among altitude training experts isn’t whether or not this type of training works, but rather which application is the most effective.
There are a few different methods of high altitude training:
Using this method, athletes both live and train at moderate altitude, often referred to as altitude camps. The athlete is continuously in a hypoxic environment. While significant physiological changes have been recorded, such as increased concentration of red blood cells and VO2max (the amount of oxygen your body can use in one minute), conflicting results are produced in regards to performance back at sea level. The higher the athlete trains, the more difficult it is to maintain the intensity of the exercise needed to produce a benefit. This “detraining effect” is what led proponents of altitude training to test other methods that allowed athletes to benefit from altitude exposure without compromising the quality of their training.
Developed in the early 90s, the live-high/train-low system allowed athletes to benefit from altitude exposure without the negative detraining effects of the live-high/train-high method. Using this approach, athletes continue their normal training at sea level, but in the evenings spend a minimum of 12 hours sleeping or resting at altitude (roughly 3,000m), usually in an altitude tent for 3-4 weeks.
A study using simulated altitude exposure for 18 days, training closer to sea level, showed significant performance gains that were still evident 15 days later. But just like any training regimen, benefits are usually lost within three weeks of the end of training. This method can also be disruptive for day-to-day commitments and have an impact on sleep quality.
Referred to as Intermittent Hypoxic Training, this method works on the premise that athletes live in their natural environment but complete up to three sessions a week of altitude training in a simulated altitude environment (altitude training chamber). Quality of training is not compromised and this method is much more convenient and less expensive for the athlete, allowing minimal disruption in home life.
The best method will vary by athlete and event, with lots of factors that need to be taken into consideration. What’s practical may not be beneficial for your particular situation, or the most beneficial method may not be exactly practical. As runners though, we’re pretty used to making sacrifices (because settling usually isn’t an option).