High altitude training: myth or misunderstanding?
by Chuck Arabas
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High altitude training for athletic performance first gained popularity just prior to the 1968 Olympics in Mexico City. Little information was available concerning adaptations, limitations and appropriate protocols for balancing stress and recovery cycles for training. Since that time, scientists and coaches have studied many variables associated with high altitude training. However, answers to the fundamental questions are still elusive. Controversy continues to swell over the issue of transference from altitude to sea level performance.
The evidence on either side of the argument leaves much to be desired. Nonetheless, it is imperative that the coaching community understand the basic physiological adaptations that are known to occur at altitude, as well as the strengths and weaknesses of research that has attempted to answer questions of performance enhancements.
The most common confusion about high altitude training is the availability of adequate oxygen. Oxygen is usually measured in percentages. For example, the air we breath is 20.93 percent oxygen, .03 percent carbon dioxide, and 79.04 percent nitrogen. These relative values are the same at all elevations. However, as one ascends in altitude, the air pressure (barometric pressure) changes significantly.
The result of less pressure is painfully obvious to the athlete. As the blood passes the alveoli in the lungs to receive its usual supply of oxygen, there is insufficient pressure exerted for the usual exchange. Under these conditions, the blood does not become as saturated with oxygen as it might at sea level. The same condition holds true when the blood passes by the muscle cell. The exchange of oxygen is diminished because there is not enough pressure to force the exchange. The athlete simply becomes inefficient at exchanging blood gases at altitude.
In order for the human body to adjust to the problem of reduced pressure, there are many changes that it must incur. Some of the changes necessary include: A release of erythropoietin (EPO). This hormone assists with an increased production of read blood cells. An increase in myoglobin. (Protein that contains iron that is found in the cytoplasm of muscle which is part of the transport system of oxygen into the mitochondria.) An increase in two and three dyphosphoglyecerate levels. This is significant because two and three DPG increase the cells ability to exchange oxygen (usually referred to as a dissociation of oxygen) allowing more oxygen to be made available to the muscle cell. A change in size and number of muscle capillary beds. And also, there is limited evidence that the buffering capacity may be increased on return to sea level. However, the mechanism for this change is not well understood nor is the change in buffering capacity well documented.
There are some disadvantages associated with high altitude training. Some of these changes include: There may be problems with weight loss due to dehydration, especially above 9,500 feet. There is evidence that a decrease can occur in both extracellular and intracellular fluid. Some of the cause for fluid loss is due to the increased ventilation that occurs to compensate for the decrease in atmospheric pressure. The greatest cause is probably due to lower production of hormones such as renin, angiotensin and aldosterone, caused by the increased stress (these hormones assist the body in retaining fluid).
The loss in water has a number of negative effects on the bodys ability to perform. For example, blood becomes more viscous, which reduces the hearts ability to pump effectively. This, in turn, causes the heart rate to increase to keep up with the demand. The effect on ATP synthesis is also greatly affected by the lack of sufficient fluids. The reduction in plasma volume diminishes the speed of transport as well as the ability of nutrients to move across the cell.
Finally, there has been some evidence that stress hormones such as cortisone, glucagon and in some cases, catecholamines, are increased at altitude. These hormones have catabolic effects in tissue.
Studies that question the effect altitude has on performance are divided. There is little evidence of refute that physiological parameters change significantly from training at altitude and most serious scientists and coaches accept the idea that performance at altitude is improved from training at altitude.
The question that continues to challenge is simple. Do these changes improve performance at sea level or are they off-set by delusions caused by the onset of stress that has been associated with training at latitude? There is considerable difficulty in answering this question due to numerous assumptions. There are many variables to control when altitude research is conducted.
Design protocol is critical in any serious research endeavor. Many research projects have been designed and implemented by inexperienced coaches or scientists who have never trained athletes at altitude. It is easy to understand why results may suggest negative effects of altitude training. Serious methodological problems can arise from inappropriate adaptation and recovery periods, too short or too long training cycles, inappropriate nutrition and hydration, variance in temperatures, or insufficient preparation and experience of the athlete in training at altitude.
Research on altitude training should utilize experienced coaches in preparatory phases and training design should be well thought out. The question is far from answered. However, since most of the top teams in the world continue to pursue altitude training, it would be unwise to discontinue the practice until sufficient evidence exists allowing for a rational change in training protocol. Thus, the question as to whether high altitude training improves swimming performance remains unanswered until more investigation can occur.