With Olympic athletes training at high altitude, and the Democratic National Convention bringing many people from sea level to the mile high city of Denver, Colorado, the physiological effects of high altitude are frequently in the news. Some people arriving at higher altitude, even to what is considered intermediate altitude (1500-2500 meters, or approximately 5000-8000 feet) can experience discomfort related to altitude. Generally, altitude sickness appears at elevations above 6500 feet, and acute mountain sickness over 8000 feet.
At higher altitudes, the barometric pressure is lower, which results in less oxygen entering the lungs per breath. The lack of oxygen can result in headache, dizziness, lack of appetite, nausea, and inability to sleep. Not all people suffer from altitude effects, and it is not known why some people suffer from altitude sickness while others do not. It is not related to how physically fit an individual is, or to age. It appears to have a genetic component.
Adaptations to High Altitude
Initially, after arriving at a higher altitude, the rate of breathing will increase to deliver more oxygen to the body. The heart rate also increases, to help deliver more oxygen to the body. Fluids redistribute; more blood flows to the brain to provide oxygen, and pulmonary blood pressure increases. If blood pressure gets too high, pulmonary edema can result.
Over time, the body begins to acclimate to the higher altitude. More red blood cells are produced, increasing the amount of oxygen that can be carried in the blood. Also, the amount of myoglobin, an oxygen carrying protein, increases. After returning to lower altitude, these adaptations will reverse.
Athletic Training
When an endurance athlete has acclimatized to a high altitude, the resulting increased red blood cell count and larger lung capacity mean they will have enhanced fitness after returning to low altitude, though after several days, their performances will return to pre-acclimatized levels. Many athletes now practice a "live high, train low" approach, where they train at lower altitude where they are able to train harder, but live at high altitude to increase their red blood cell count. In fact, some athletes are trying to replicate this effect by sleeping in chambers that mimic the conditions of high altitude, allowing them to train anywhere, instead of needing to live in the mountains.
Resources
Pollard, AJ and Murdoch, DR. (2003) The High Altitude Medicine Handbook, Radcliffe Publishing.
Wilber, RL. (2007) "Application of altitude/hypoxic training by elite athletes." Medicine and Science in Sports and Exercise. 39, 1610-1624.
Tamara Golden - Tamara Golden is a professional science and technical writer providing materials to biotechnology and nonprofit clients. She enjoys ...
