Altitude training

The study of altitude training was heavily delved into during and after the 1968 Olympics, which took place in Mexico City, Mexico: elevation . It was during these Olympic Games that endurance events saw significant below-record finishes while anaerobic, sprint events broke all types of records. It was speculated prior to these events how the altitude might affect performances of these elite, world-class athletes and most of the conclusions drawn were equivalent to those hypothesized: that endurance events would suffer and that short events would not see significant negative changes. This was attributed not only to less resistance during movement—due to the less dense air—but also to the anaerobic nature of the sprint events. Ultimately, these games inspired investigations into altitude training from which unique training principles were developed with the aim of avoiding underperformance. ==Training regimens==

Athletes or individuals who wish to gain a competitive edge for endurance events can take advantage of exercising at high altitude. High altitude is typically defined as any elevation above . Live-high, train-low One suggestion for optimizing adaptations and maintaining performance is the live-high, train-low principle. This training idea involves living at higher altitudes in order to experience the physiological adaptations that occur, such as increased erythropoietin (EPO) levels, increased red blood cell levels, and higher VO2 max, while maintaining the same exercise intensity during training at sea level. Due to the environmental differences at high altitude, it may be necessary to decrease the intensity of workouts. Studies examining the live-high, train-low theory have produced varied results, which may be dependent on a variety of factors such as individual variability, time spent at high altitude, and the type of training program. For example, it has been shown that athletes performing primarily anaerobic activity do not necessarily benefit from altitude training as they do not rely on oxygen to fuel their performances. A non-training elevation of and training at or less has shown to be the optimal approach for altitude training. Good venues for live-high train-low include Mammoth Lakes, California; Flagstaff, Arizona; and the Sierra Nevada, near Granada in Spain. Altitude training can produce increases in speed, strength, endurance, and recovery by maintaining altitude exposure for a significant period of time. A study using simulated altitude exposure for 18 days, yet training closer to sea-level, showed performance gains were still evident 15 days later. Opponents of altitude training argue that an athlete's red blood cell concentration returns to normal levels within days of returning to sea level and that it is impossible to train at the same intensity that one could at sea level, reducing the training effect and wasting training time due to altitude sickness. Altitude training can produce slow recovery due to the stress of hypoxia. Exposure to extreme hypoxia at altitudes above can lead to considerable deterioration of skeletal muscle tissue. Five weeks at this altitude leads to a loss of muscle volume of the order of 10–15%. Live-high, train-high In the live-high, train-high regime, an athlete lives and trains at a desired altitude. The stimulus on the body is constant because the athlete is continuously in a hypoxic environment. Initially VO2 max drops considerably: by around 7% for every 1000 m above sea level. Athletes will no longer be able to metabolize as much oxygen as they would at sea level. Any given velocity must be performed at a higher relative intensity at altitude. RSH is still a relatively new training method and is not fully understood. Artificial altitude Altitude simulation systems have enabled protocols that do not suffer from the tension between better altitude physiology and more intense workouts. Such simulated altitude systems can be utilized closer to competition if necessary. In Finland, a scientist named Heikki Rusko has designed a "high-altitude house." The air inside the house, which is situated at sea level, is at normal pressure but modified to have a low concentration of oxygen, about 15.3% (below the 20.9% at sea level), which is roughly equivalent to the amount of oxygen available at the high altitudes often used for altitude training due to the reduced partial pressure of oxygen at altitude. Athletes live and sleep inside the house, but perform their training outside (at normal oxygen concentrations at 20.9%). Rusko's results show improvements of EPO and red-cell levels. Artificial altitude can also be used for hypoxic exercise, where athletes train in an altitude simulator which mimics the conditions a high altitude environment. Athletes are able to perform high intensity training at lower velocities and thus produce less stress on the musculoskeletal system. == Principles and mechanisms ==

Altitude training works because of the difference in atmospheric pressure between sea level and high altitude. At sea level, air is denser and there are more molecules of gas per litre of air. Regardless of altitude, air is composed of 21% oxygen and 78% nitrogen. As the altitude increases, the pressure exerted by these gases decreases. Therefore, there are fewer molecules per unit volume: this causes a decrease in partial pressures of gases in the body, which elicits a variety of physiological changes in the body that occur at high altitude. The physiological adaptation that is mainly responsible for the performance gains achieved from altitude training, is a subject of discussion among researchers. Some, including American researchers Ben Levine and Jim Stray-Gundersen, claim it is primarily the increased red blood cell volume. Others, including Australian researcher Chris Gore, and New Zealand researcher Will Hopkins, dispute this and instead claim the gains are primarily a result of other adaptions such as a switch to a more economic mode of oxygen utilization. Increased red blood cell volume At high altitudes, there is a decrease in oxygen hemoglobin saturation. This hypoxic condition causes hypoxia-inducible factor 1 (HIF1) to become stable and stimulates the production of erythropoietin (EPO), a hormone secreted by the kidneys, EPO stimulates red blood cell production from bone marrow in order to increase hemoglobin saturation and oxygen delivery. Some athletes demonstrate a strong red blood cell response to altitude while others see little or no gain in red cell mass with chronic exposure. It is uncertain how long this adaptation takes because various studies have found different conclusions based on the amount of time spent at high altitudes. While EPO occurs naturally in the body, it is also made synthetically to help treat patients with kidney failure and to treat patients during chemotherapy. Over the past thirty years, EPO has become frequently abused by competitive athletes through blood doping and injections in order to gain advantages in endurance events. Abuse of EPO, however, increases RBC counts beyond normal levels (polycythemia) and increases the viscosity of blood, possibly leading to hypertension and increasing the likelihood of a blood clot, heart attack or stroke. The natural secretion of EPO by the human kidneys can be increased by altitude training, but the body has limits on the amount of natural EPO that it will secrete, thus avoiding the harmful side effects of the illegal doping procedures. Other mechanisms Other mechanisms have been proposed to explain the utility of altitude training. Not all studies show a statistically significant increase in red blood cells from altitude training. One study explained the success by increasing the intensity of the training (due to increased heart and respiration rate). In a study comparing rats active at high altitude versus rats active at sea level, with two sedentary control groups, it was observed that muscle fiber types changed according to homeostatic challenges which led to an increased metabolic efficiency during the beta oxidative cycle and citric acid cycle, showing an increased utilization of ATP for aerobic performance. Due to the lower atmospheric pressure at high altitudes, the air pressure within the breathing system must be lower than it would be at low altitudes in order for inhalation to occur. Therefore, inhalation at high altitudes typically involves a relatively greater lowering of the thoracic diaphragm than at low altitudes. ==See also==