Altitude training: Does it work?

Dear Interested,

Hypoxic training is a type of athletic training used to improve athletic performance at normal altitudes or allow athletes, such as mountain climbers, to perform better at high altitudes by depriving the body of oxygen. Hypoxic training is commonly achieved by using specific training regimens at high altitudes and is most often used by distance runners, swimmers, and cyclers. The idea became popular after the 1968 Olympic Games, which were held in Mexico City, at an elevation of 7,545 feet — even higher than Denver, Colorado. Experts began to hypothesize about how the Olympians’ bodies were adapting to performing at such a high altitude, and by the 1990s, had developed several different types of hypoxic training, including intermittent hypoxic exposure during rest (IHE), intermittent hypoxic exposure during a continuous session (IHT), and the most popular, "live high, train low" (LHTL). While the methods each have their differences, they all aim to acclimate the body to high altitudes, where the air is "thinner" or contains less oxygen.

If you've ever been hiking several thousand feet above sea level, you may have felt that normal activities, such as walking, became more difficult. This is because there is less oxygen available per breath and therefore less oxygen traveling to the organs and muscles of the body, increasing heart rate and blood pressure and decreasing respiratory ability which may make activity harder. However, over time at high altitudes the body adapts and eventually increases the number of red blood cells in the blood, which carry oxygen throughout the body. By adding more red blood cells, the body can use the oxygen available in the air more efficiently. Recent studies show that other systems of the body may be adapting as well, such as the respiratory, muscular, and nervous systems. Once this adaptation occurs, athletes can return to normal altitudes, and still have extra oxygen available, which prevents fatigue while increasing lactic acid tolerance and endurance. Research has shown that this boost can increase athletic performance in elite athletes by nearly two percent, which may make all the difference during a photo finish in, for example, Olympic swimming. That being said, for those not qualifying for the Olympics, the benefits are less pronounced, and some "simulated" altitude devices on the market don't always live up to the claims in their advertisements (more on that later).

As mentioned earlier, there are several different types of hypoxic training, each with slightly different methods and physiological results.

• "Live high, train low" (LHTL) is a training program where athletes spend most of their day (about 12 to 16 hours) living in high altitudes around 8,000 feet above sea level, optimally for about four weeks at a time. They may train there as well but only at lower intensity. Then, for a few hours a day, they train at higher intensity at normal elevation. In the U.S, this method is used by many elite athletes, including runners at a popular training camp in Utah. During training, they live in Park City, Utah (about 7,000 to 8,000 feet above sea level) but train in Salt Lake City (about 4,000 feet). 
• Intermittent hypoxic exposure during rest (IHE) involves exposure to low-oxygen (or high-altitude) environments for short periods of time. Between periods, the athlete returns to regular oxygen and altitude, and the process is repeated many times for up to a few weeks. One study showed that 90 minutes of exposure, nine times over three weeks, showed increases in red blood cell counts among other physiological changes. Other studies show similar results with some variations in exposure duration and length of training. However, these haven't necessarily translated to recorded increases in performance.  
• Intermittent hypoxic exposure during a continuous session (IHT) is similar to IHE, because exposure to low-oxygen environments is limited to short periods repeated over a few weeks. However, during the short exposures of IHT, the athlete also completes high intensity exercise. While this seems contradictory to the other methods, some changes in muscles and other parts of the body have been observed in several studies; likely because high altitude training adds additional rigor to a training routine. 

While the benefits of these hypoxic training methods, particularly LHTL, have been proven in elite athletes, some say using training to change the body's physiology constitutes an unfair advantage. Also, the potential benefits to athletes at lower performance levels or who participate in less intensive training regimens still lacks evidence in the research (although scientists are exploring currently whether living in high altitude could increase health and longevity). In some cases, hypoxic training may also have negative health impacts. For one, constant low levels of oxygen can cause poor sleep or altitude sickness, with symptoms such as nausea and vomiting, headaches, and fatigue. Over time, this may cause chronic stress, detraining, and edema (fluid buildup). It's also possible for blood to thicken too much at high altitudes, raising the risk of death due to blood clotting. Being a few thousand feet up can also increase exposure to ultraviolet (UV) rays, which may contribute to skin cancer and cataracts. To avoid these conditions, it's recommended to increase altitude slowly, start with very low training intensity, and talk with a health care provider to review factors such as blood iron levels or other pre-existing conditions before starting any hypoxic training.

Heading for the hills also isn't the only way to achieve the effects of hypoxic training. As you mentioned, there are now many ways to simulate high altitude training: breathing intermittently with a nitrogen mask, sleeping in a nitrogen tent, living or sleeping in a barometric chamber, and living in a nitrogen house. Nitrogen replaces a proportion of the oxygen in the air in many of these methods, leading to oxygen deprivation and therefore creating a hypoxic environment. However, these tools aren't considered effective methods for conducting hypoxic training. The use of altitude masks, for example, is ineffective because it puts resistance on the lungs, but doesn't cause the same acclimation as living in high altitude. Altitude tents or chambers are also ineffective since one would have to spend most of their day inside to simulate the high-altitude environment necessary to accomplish hypoxic training.

Using altitude-simulating devices isn't likely to bring athletic improvement, but if you decide to try them for yourself you may want to take precautions to prevent sickness or other negative impacts. If you're interested in pursuing high-altitude training, you may want to talk to a health care provider first to ensure your safety throughout your physical activity or connect with a certified trainer to discuss the best methods. However, what's much more certain to improve a person's athletic potential are lifestyle choices such as getting plenty of sleep, eating a balanced diet, practicing stress reduction strategies, and strength training (among others).

Best of luck in your athletic adventures!