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By Dr Mimi Zimwalt, MD

Hypoxic Dose on Exercise-Hype, Hope of Height?

Training at elevated altitudes is becoming more and more popular as a mode of exercising in an environment of low oxygen, as an attempt to improve cardiorespiratory condition in hopes of enhancing athletic performance. Researchers began to study high altitude training in the late 1960s, especially after the Olympics in Mexico City being held at over 7300ft elevation. World-class elite athletes participating in anaerobic, sprint-type events broke all sorts of records, while those competing in endurance Olympic Games finished way below prior recorded times. Speculations arose out of these differing competition results center on the air being less dense, therefore providing less resistance during motion, along with shorter duration of non-aerobic events contributing to the overall final advantage.

So what are the principles/mechanisms behind altitude training? The atmospheric pressure between high altitude and sea level differs by the former having less molecules of gas (~4/5 nitrogen-~1/5 oxygen), thus being thinner and exerting less force in the body. This decrease in air resistance causes different physiological changes. The higher elevation results in less oxygenation of blood, causing an increase in EPO-erythropoietin (produced in the kidneys). This hormonal production sends signals to the bone marrow to make more red blood cells (RBCs), but this adaptive effect is variable in different athletes, according to their body’s natural limits of natural EPO secretion. Another bodily change occurs from increasing workout intensity from elevated respiratory/heart rates, causing an improvement in the training effect, which can last up to a couple of weeks after returning to sea level. Similarly, other research has shown that hypoxic training stimulates muscles to use oxygen more efficiently, contributing to improved endurance/duration of activity. In addition, by exercising at higher altitudes, muscle fiber types eventually switches towards better aerobic capacity/performance, due to alteration of cellular metabolism.

How can someone then go about using altitude-training effect to his/her advantage? Few techniques exist to help an athlete achieve the natural condition of hypoxic atmosphere. One such condition is living high (~7000 to 8000ft above sea level) and exercising low ~4000ft or less, is optimal for altitude-type training. One must be exposed to higher altitudes of at least 12hrs/day for about 3 weeks, before physiological changes occur to make a positive difference in performance, which can persist as long as 2 weeks at sea level. The gains in speed, strength, endurance, plus recovery are variable according to time spent along with training program type. These physical effects are also less evident in athletes engaged in primarily anaerobic activity, since they don’t rely on oxygen as fuel for energy. However, it’s not recommended to train at altitudes higher than 16000ft, since this degree of extreme exposure to hypoxia can deteriorate soft tissues, resulting in 10-15% muscle loss. Other methods of hypoxic exercising include using artificial altitude training systems (Hypoxico, Inc) or working out inside altitude simulators/barometric chambers, first introduced in mid 1990s. Since then, respiratory muscle training (RMT)/resistive breathing while exercising has surfaced as another tool to train similar to simulated altitude environment, via usage of a mask-like device with valves providing resistance with each breath.

The elevation-training mask (ETM) is a new product on the market composed of a multi-level resistance system, supposedly designed to help with sports performance. This wearable device has adjustable opening/valves to increase resistance to respiration, which makes breathing more difficult. Individualized adjustments allows the athlete to purportedly control simulated level between ~3000-18000ft altitude range. A recent study on cyclists did show some differences in respiratory muscle endurance parameters, but not comparable to working out at naturally elevated height conditions.

In summary, results of high altitude training via natural or artificial/simulated elevated height hypoxic environmental conditions, including devices touting potential positive effects on sports performance, are negligible at best. Positive physiological changes do occur in the body dependent on frequency/duration of exposure. As far as better oxygen utilization and/or improved respiratory muscle function are concerned, these effects happen primarily in endurance events. However, whether these adaptations will translate to boosting athletic activity needs to be studied further. Newest scientific evidence is still lacking, so try not to waste your money on any ETMs, especially if you’re involved in anaerobic types of exercise. Thus far it’s much more hype than help. The best approach is to live high-train low, or better yet, perform sports-specific training on a regular basis to ultimately maximize your physical competitive condition…


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