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1955 Pan American Games, acclimatization, acetazolamide, acidity, acute mountain sickness, aerobic, alcohol, alkaline, altitude, altitude sickness, AMS, anaerobic, apnea, bicarbonate ions, biking, carbon dioxide, cardiovascular workout, elevation, elevation training, endurance, EPO, ergogenic, erythropoietin, fitness, Gamwow bag, HACE, HAPE, HARH, hemoglobin, high altitude cerebral edema, high altitude pulmonary edema, high altitude retinal hemorrhage, high altitude sickness, high elevation training, hiking, hyperbaric chamber, hypnotic medication, hypoxic conditions, lactic acid, live high train high, live high train low, live low train high, mountain climbing, nifedipine, oxygen, periodic breathing, pH scale, rock climbing, sea level, skiing, soccer, sprinting, swimming, weight training, yoga.
Altitude training refers to exercise at varying elevations to maximize physical fitness.
Some experts define high altitude as any elevation at least 2,000 meters (about 6,500 feet) above sea level. Other experts set the limit at 2,400 meters (about 8,000 feet) above sea level, the elevation at which 25% of people experience symptoms of altitude sickness.
Athletes who train or live at high altitudes may gain a competitive advantage against athletes who train or live at sea level or moderately high altitudes (about 300 meters/1,000 feet) due to physiological changes in the body in response to the high altitude.
Evidence shows that some types of altitude training may help endurance athletes (those who exercise for long periods of time), as well as sprinters (those whose events are intense but last for less than two minutes). Some programs may also help mountain climbers, skiers, and rock climbers prepare for exercise at very high elevations (above 2,700 meters, or about 9,000 feet). Altitude training may help elite athletes as well as recreational athletes and may help people preparing for competition in many sports, including running, swimming, and soccer. However, some athletes experience no benefit from altitude training. It is impossible to predict how and when the body may respond to altitude training or if an individual will respond at all.
Competitive athletes who train at high altitudes for 3-4 weeks may experience benefits to their athletic performance for a few days or weeks after returning to lower altitudes, according to some studies. These benefits may last for about three weeks.
Those preparing for high-elevation sports, such as hiking, skiing, and rock climbing, should, while at low elevations, engage in cardiovascular training, which strengthens the heart, increases endurance, and trains muscles to be more efficient. Ascents should be slow, and hikers should spend days higher and nights lower to make sure that the body can handle the high elevation without becoming ill.
History: Athletes and coaches began to recognize the importance of altitude in sports training during the 1955 Pan American Games in Mexico City, which is 2,300 meters (about 7,500 feet) above sea level. Many of the athletes from lower elevations needed oxygen masks; some collapsed from lack of oxygen. At that elevation, differences in the atmosphere caused performances to vary from what they would have been at a lower altitude. Those competing in endurance events (events lasting longer than two minutes) did not perform as well as expected. It was hypothesized that the athletes may perform better if they train at high altitudes and compete at lower altitudes. Experts soon learned that sprinters may also benefit from training at high altitudes.
Atmosphere changes: As altitude increases, air becomes less compressed, reducing the oxygen available. Although the proportion of oxygen remains the same relative to other gasses, it is more spread out across space than it is at lower elevations. At 3,000 meters (about 10,000 feet), the level of oxygen in the blood may be as low as 69% of its sea-level value, according to the U.S. Centers for Disease Control and Prevention.
Physiological changes: When ascending to high altitudes, the human body may undergo physiological changes to compensate for changes in the atmosphere. These changes take days or weeks to occur but may last weeks after returning to lower elevations. Pinpointing when these changes occur is difficult, as they depend on the person, the elevation, the fitness level, and the length of time spent at high and low elevations, among other variables.
When a person moves from low to high altitudes, the body acclimatizes. The heart and breathing are the first to change, increasing in rate. Over a few days, the body uses what little oxygen is available more efficiently. Some studies suggest that changes in muscle function and the ability to handle carbon dioxide waste may occur if the person remains at a high elevation for a few weeks.
Risks: Training at high elevations may not yield any competitive advantage. In fact, it may even reduce athletic potential in some cases. Some evidence suggests that athletic potential may be maximized by living at altitudes of 2,000-2,500 meters (about 6,500-8,200 feet), while training at lower elevations (sea level to 1,250 meters, or about 4,000 feet).
Training at high elevations also carries some health risks, such as altitude sickness, which is characterized by poor sleep, nausea, fatigue, and headaches. Altitude sickness may impede athletes' ability to train effectively. However, only about 25% of athletes may experience more than two symptoms of altitude sickness at 2,500 meters (about 8,200 feet); these symptoms typically cease within 1-5 days of being at high elevation. Altitude sickness may be prevented by taking medication or ascending slowly.
General: Physiological changes in the body may occur at high elevations and may increase athletic performance. Different altitude training programs may use these physiological changes to increase performance at lower altitudes or, in the case of high- altitude sports such as mountain climbing, hiking, and skiing, to help athletes better adjust to intense physical activity at very high altitudes.
Physiological effects: Several physiological changes occur in the body at high elevations that may be responsible for increases in athletic performance; these include increased absorption of oxygen in the blood and loss of carbon dioxide, leading to changes in the pH level (acidity and alkalinity) of the body.
Oxygen: More oxygen in the blood may improve athletic performance, and at high altitudes, the blood absorbs more oxygen. Absolute oxygen levels are higher at sea level than at higher elevations. At high elevation, the body must use what little oxygen is available in the air more efficiently. Oxygen is contained in the blood by hemoglobin, a protein in red blood cells. The kidneys sense when oxygen levels are low, and to correct this, they secrete a hormone called erythropoietin, which signals bone marrow to produce more red blood cells. With more red blood cells, there is more hemoglobin and thus more oxygen. The excess oxygen-carrying capacity can partially compensate for less oxygen being available from the air. At high elevations, the body is prepared to use oxygen efficiently, which is useful during intense periods of exercise. Back at low elevations, the blood is able to use oxygen more efficiently than it could before being at high elevations, improving athletic performance at low elevations.
Some experts recommend taking iron supplements to support the body's production of additional red blood cells. More research is needed to determine whether this technique is effective.
Carbon dioxide: People breathe faster to have enough oxygen while training and at high altitudes. Increase in breathing rate means a person is exhaling more carbon dioxide. However, with the loss of this acidic gas, the body becomes more alkaline. The body needs to adjust the balance of its acidity and alkalinity, also referred to as its pH (potential Hydrogen) scale. The body's pH level is stabilized with the help of the kidneys, which remove alkaline bicarbonate ions from the blood. These ions are excreted through urine. At high elevations, the body is prepared for regulating an alkaline pH level, a condition that also occurs during endurance workouts.
Muscles: At high elevations, the body's muscles are able to manage the buildup of waste acid more efficiently. Athletes who sprint use an anaerobic metabolic process, rather than oxygen, to create energy. The anaerobic process produces lactic acid, which may build up in muscles and may limit sprinting activities. Some evidence suggests that after training at high altitudes, the muscles may have an increased ability to absorb acid. The authors suggest that this may improve sprinting performance. This may help short-distance runners, swimmers, and other athletes who use short bursts of energy.
Types of altitude training: Biking, running, weight lifting, rock climbing, and swimming are all types of exercises that athletes can use to train. Team sports, such as soccer and tennis, may be practiced at high elevations. At high elevations, these workouts may need to be less intense than they would be at lower elevations to accommodate for less oxygen in the atmosphere. Workouts may need to start at a lower intensity when athletes are still acclimatizing to the high elevation and slowly start increasing in intensity after a few days. Athletes may never be able to train at the same high intensity at high elevations as they could at low elevations.
There are three main training programs for competitive athletes that use altitude: "live high, train low," "live high, train high," and "live low, train high."
Live high, train low: This workout regime requires athletes to spend most of their time at high altitudes, but they move to low altitudes to train. Some studies have shown that after four weeks of "live high, train low," the body may undergo physiological changes that improve performance. Although the "live high, train low" program has the strongest supportive evidence of effectiveness, not all studies concur.
Live high, train high: This exercise regime provides continuous exposure to high altitudes, where athletes both live and train at high elevations. Although it is the most common program that coaches and athletes use, there is mixed scientific evidence for its effectiveness.
Live low, train high: With this exercise program, athletes spend more of their time at low elevations, but move to higher elevations to train. The scientific evidence of effectiveness for this training program is not well-established.
Locations: Finding a place to train high and live low may be logistically difficult. The high elevation must be easily accessible to the low elevation, and both elevations must have facilities for athletes to train. There are several locations where athletes have found they can move easily between high and low altitudes. One such location is in Utah, between Park City (2,100 meters, or about 7,000 feet) and Salt Lake City (1,280 meters, or about 4,200 feet), which are 30 minutes apart.
High-elevation sports: Athletes who are preparing for sports that take place at high elevations, such as mountain climbers, skiers, and hikers, may need to train carefully for these sports before engaging in them. Cardiovascular workouts such as long-distance running while close to sea level help these athletes use oxygen and muscles more efficiently once at high elevations. Gradually increasing their elevation and the intensity of workouts helps these athletes manage exercising at high elevations.
Artificial elevation: Some gyms provide technologies that simulate high-altitude atmospheric conditions. These include rooms that have lower oxygen levels and masks that deliver air with less oxygen. There is some equipment athletes can use to simulate high altitudes. One example is a tent that recreates the low-oxygen air pressure of high altitudes. Athletes sleeping in the tent may produce more hemoglobin, using oxygen more efficiently during workouts.
General: Evidence of effectiveness for altitude training is mixed. This may be because of inconsistencies in the methods of experiments, as well as highly variable physiological responses to high attitudes among individuals.
Study participants: Some studies use elite athletes as subjects, others use recreational athletes, and still others use animals. This may explain some inconsistencies in the effectiveness of altitude training.
Inconsistent benefits: Altitude training may be beneficial only for some athletes. Some researchers have reported that among non-elite athletes who lived high and trained low, 31% may not experience improved performance. More research is needed to determine why some people may benefit from altitude training and others may not. Currently, some experts believe genetics may play a role in these differences. The evidence is unclear, but some individuals' bodies may be more sensitive and responsive to decreases in oxygen levels. People who have developed severe forms of mountain sickness are encouraged to register with a database that may be used in genetic studies.
Risks of training high: Any workout program that requires training at a high elevation may not be effective because training at high altitudes is more difficult than training at low altitudes. Athletes have difficulty breathing while training at higher altitudes because of reduced oxygen concentrations. As a result, athletes may feel that their workouts are as intense up high as they are at lower elevations, but they may not be. Although athletes may acclimatize within 3-5 days, they may never be able to train as intensely as they could at sea level. When the athletes compete with those who trained at lower altitudes, they may be at a lower level of fitness. Therefore, training low while living high is likely the most effective training program.
Small benefit: Some research suggests that the "live high, train low" program, which is generally considered the most effective of the three programs, only yields a 1-2% improvement in performance once back at lower elevations. This may only be enough improvement for elite athletes to notice. Another study compared endurance athletes who "lived high, trained low" to those who "lived high, trained high" and who "lived low, trained low." During a sea-level five-kilometer (3.1-mile) run, athletes who "lived high, trained low" shortened their times by 13.4 seconds. Those who "lived low, trained high" ran about the same time, and those who both lived and trained low slowed down by about 26 seconds. Elite athlete times for this event are just more than 14 minutes for women and about 13 minutes for men. Saving 13 seconds on their time may be significant for elite runners, but less significant for recreational runners.
High-altitude competition: The evidence is clear that if the competition is in a high-altitude location, it is important for athletes to train and live at a similarly high location. High-elevation training may prevent performance deterioration when a competition is at a high elevation, but it is less likely to help when competition is at a low elevation. Had Pan-American athletes participating in a 1955 endurance event been prepared for the high Mexico City elevation, they may not have seen such a decline in their performance. A British Medical Journal study showed that soccer teams competing in South America who lived and played at high-altitude places, such as Bolivia, were more likely to win against opponents who generally lived and played at lower-elevation places, such as Brazil. This was most likely the case when the match was being held at a high altitude. The authors found that for every 1,000 meters (about 3,300 feet) difference between where the two teams lived and trained, the score favored the high-altitude team by a half point.
It is also important for people engaging in sports that take place in high altitudes, such as mountain climbers and skiers, to train carefully at high elevations. Sudden vigorous activity at high altitudes may cause serious health problems.
Inconsistent response: Knowing how an athlete may respond to altitude is difficult; the athlete may become ill from altitude sickness and be unable to train, or may not experience benefits once at lower altitudes or may only experience these benefits weeks after returning. Determining whether the athlete has benefited from altitude training is also difficult and may require blood tests. Some athletes may show immediate improvements; others may take weeks to show improvements. Improvements may also be due to changes in other variables, such as exercise techniques, nutrition, air quality, or sleep, rather than altitude training.
Duration: Based on available scientific evidence, it is unclear how long an athlete should live or train in high altitudes. However, many coaches and athletes participate in programs lasting 3-4 weeks at high altitudes, whether living, training, or both. Skiers and mountain climbers may benefit from a few days to a few weeks at high altitudes before ascending any further.
Change in climate: When athletes train at high elevations and return to lower altitudes for competitions, some may be unaccustomed to the climate. They may have become accustomed to the cool, dry mountain air, and their bodies may not be prepared to compete in the hot, humid, or even polluted conditions that are common at lower altitudes. Some research suggests that sudden exposure to hot, humid temperatures may limit the effects of having trained at high altitudes.
Change in location: Coping with some symptoms of altitude sickness may be stressful for athletes. For example, the poor sleep with vivid dreams and fatigue associated with altitude sickness may disrupt training. Moving to a high location may involve travel, extra monetary expense, and being away from home, potential sources of stress for some athletes.
Finding a location: Finding a location where it is convenient to move from high to low altitude is difficult. One study used Park City (2,100 meters, or about 7,000 feet), and Salt Lake City (1,280 meters, or about 4,200 feet), both in Utah and 30 minutes apart, as their high and low living and training sites. If an area with high and low regions close together is difficult to find, athletes may train with an oxygen mask. This mask delivers air with lower levels of oxygen to athletes as they train. Some athletes live at sea level, but sleep in a tent that may create the atmospheric conditions of high altitudes.
Ethics: There is some ethical debate about altitude training. Erythropoietin (EPO) is the hormone that the kidneys secrete to create more red blood cells. Ultimately, this hormone helps people use oxygen more efficiently. Athletes may receive EPO intravenously, but this is prohibited in many leagues and athletic associations. Moving to a high altitude is a natural way to encourage the increased production of the hormone. Some athletic associations test athletes for abnormally high EPO levels, along with illegal drugs. Levels could be high if the athlete received an intravenous dose of EPO or was living or training at a high altitude. However, officials may not be able to tell the difference.
Another potential ethical dilemma surrounds technologies people use to simulate high altitudes without actually leaving at sea level. Sleeping in a tent that controls the air pressure to mimic high-elevation atmospheric conditions may be considered artificial, and therefore some believe it might be unethical.
General: Risks associated with living and training at high altitudes may be life-threatening, while some may merely decrease athletic performance.
Altitude sickness: Altitude sickness, also called mountain sickness, covers a wide variety of physical problems that may result from being at a high elevation. Acute mountain sickness, high altitude pulmonary edema, high altitude cerebral edema, and high altitude retinal hemorrhage are all types of altitude sickness.
Acute mountain sickness (AMS): Symptoms include poor sleep, lethargy, loss of appetite, nausea, rapid heart rate, shortness of breath with exercise, and headaches. These symptoms typically develop within a few hours of moving to an elevation as low as 2,000 meters (about 6,500 feet).
AMS may make training more difficult; working out may in turn increase the severity of altitude sickness symptoms. Furthermore, nausea and vomiting may lead to a decrease in appetite, further impairing an athlete from training effectively.
High altitude pulmonary edema (HAPE): This condition occurs when oxygen concentration in the air is so low that fluid begins to build up in the lungs. Experts do not know why the lungs fill with fluid, but it may cause the lungs to become even less able to take in oxygen from the air. Risk of developing HAPE increases with elevation.
Breathlessness while at rest indicates that the lungs are not able to supply enough oxygen to the body, a warning sign of HAPE. Two other symptoms are a cough with pink, frothy phlegm and an accelerated heart rate. Vigorous exercise may increase the risk of developing HAPE.
High altitude cerebral edema (HACE): HACE is the buildup of fluid in the brain. It is characterized by headaches, vomiting, lethargy, and bizarre or irrational behavior. The symptoms may progress to confusion, unsteadiness, and even coma. The risk of HACE also increases with elevation.
High altitude retinal hemorrhage (HARH): HARH refers to bleeding in the back of the eye and may occur at extremely high elevations (2,700 meters, or about 9,000 feet). There are often no symptoms, but some people may develop a blind spot in the eye. HARH is diagnosed with an instrument called an ophthalmoscope, which views the eye. HARH is unlikely to cause permanent damage.
HAPE, HACE, and HARH occur rarely. The risks are greater for mountain climbers and skiers ascending to extremely high elevations (above 2,700 meters, or about 9,000 feet) rather than athletes training for competitions held at lower elevations.
Poor sleep: Many people do not sleep well at high altitudes. Vivid dreams, feelings of suffocation, and tiredness upon waking have been reported. At high elevations, some people experience periodic breathing during sleep. This means that while sleeping, they alternate between a few deep breaths and a few shallow breaths. Others may develop sleep apnea, a short pause in breathing. Apnea and periodic breathing may cause fluctuations in heart rate and may wake a person up, creating a sense of restlessness. Poor sleep may contribute to fatigue, decreased physical performance, and a greater risk for injury.
Cough: Some athletes, such as hikers and mountain climbers, develop a persistent cough at high elevations. The reasons are not well-understood, but some experts believe this may be due to excess fluid in the lungs.
Poor environmental conditions: Conditions at high altitudes may be risky or hazardous. The temperature may become cold and dry, with increased exposure to ultraviolet (UV) radiation. This may lead to sunburn and dehydration. Drinking enough fluids is important for all athletes, especially at high elevations. Storms and windy conditions may limit mobility on a mountain or create hazardous conditions for driving or exercising.
Medical conditions: Athletes with heart disease or sickle-cell disease should consult with their health care provider before training at high altitudes. Altitude illness may cause diabetic ketoacidosis, a potentially life-threatening condition caused by high glucose levels and low insulin levels. People who take medications that depress the respiratory system should not travel to high altitudes.
Treatment: Altitude sickness may be treated by descending, breathing oxygen through a mask, creating conditions of higher pressure using technology (e.g., a portable hyperbaric chamber), or medications.
Oxygen and pressure-based treatments: A portable hyperbaric chamber, called a Gamwow bag, is an inflatable bag that a person can lie in. The bag mimics the atmospheric conditions of a lower atmosphere. Athletes with AMS may inhale about 2-4 liters of oxygen per minute; this increases the amount of oxygen in the blood.
Medications: Athletes can take acetazolamide (Diamox®) before they ascend and after symptoms of altitude sickness develop. This medication makes the blood more acidic, which increases respiration and therefore oxygen. The U.S. Centers for Disease Control and Prevention (CDC) recommend 125 milligrams every 12 hours before ascent and for the first two days at high altitude.
Nifedipine (Procardia®) is an antihypertensive drug that may prevent and treat HAPE by decreasing pressure in the pulmonary artery, allowing more oxygen to transfer.
A steroid called dexamethasone (Decadron®) increases the amount of bicarbonate excreted in the urine, making the blood more acidic. This may treat AMS, HACE, and sometimes HAPE. This may make the athlete feel acclimatized, without symptoms of mountain sickness, but he or she should continue taking measures to prevent mountain sickness.
Two hypnotic medications, zaleplon (Sonata®, Starnoc®) and zolpidem (Ambien®, Nytamel®), both used to treat insomnia, have been shown to improve sleep and increase the amount of oxygen in the blood at very high altitudes. Improved sleep was associated with fewer and less severe AMS symptoms at 3,500 meters (about 11,400 feet). More study is needed before recommendations can be made.
Integrative therapies: Some scientific evidence shows that yoga may help increase respiratory efficiency. There is limited, inconclusive evidence that Ginkgo biloba may help treat altitude sickness. There is also inconclusive evidence that antioxidants, such as vitamin E with carotene, may help keep respiratory changes more consistent between low and high elevations.
Integrative therapies with unclear scientific evidence: Reishi mushroom (Ganoderma lucidum), also known as Ling Zhi in China, has been used to treat and prevent altitude sickness. It is found on decaying logs. Rhodiola, a plant that grows in high-altitude regions, has been used in Eastern Europe and Asia to protect against reduced oxygen in the blood. Neither of these supplements has been clinically tested.
Prevention: Ascending at a slow rate rather than flying or driving directly from low to high altitudes may prevent altitude sickness. The CDC recommends that athletes should ascend no more than 900 meters (about 3,000 feet) per day. Training before the body has acclimatized to a high elevation might exacerbate symptoms. Alcohol use may also make symptoms worse, so drinking is not recommended for the first few days after ascending. Finally, dehydration may exacerbate altitude sickness, so athletes should drink plenty of fluids.
Altitude training is just one technique athletes may use to increase their performance, and it may well be effective, especially for those who may compete at high altitudes. However, a carefully crafted exercise program as well as adequate nutrition and sleep are also important factors for all athletes looking for high performance.
This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).
Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.
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Natural Standard: The Authority on Integrative Medicine. www.naturalstandard.com
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U.S. Centers for Disease Control and Prevention (CDC). www.cdc.gov
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Copyright © 2013 Natural Standard (www.naturalstandard.com)
The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.
March 22, 2017