As experienced mountaineers can attest, altitude is no joke. If you increase altitude too quickly, you'll find yourself with a monstrous headache at best -- at worst, you'll experience acute altitude sickness, which can lead to potentially lethal conditions such as pulmonary or cerebral edema.
At sea level, the weight of the atmosphere above compresses the air around us. As we travel upward, air pressure lessens. Technically, there's the same amount of oxygen in mountain air as in sea level air; however, the lighter pressure at altitude means that oxygen molecules are further apart [source: Baillie]. Because the air at altitude is thinner, we have to work harder to extract the same amount of oxygen.
It's tricky to predict how an athlete's body will respond to altitude. Faster breathing and a higher heart rate are natural responses to acclimatization; however, if an athlete is breathless even at rest, he or she may be in danger of developing more serious altitude-related conditions, such as:
- Sluggish blood flow. One of the most desirable benefits of altitude training, an increase in red blood cell production, can actually make blood thicker and stickier. The heart sometimes has trouble pumping the blood effectively, which reduces oxygen flow and negates the benefit of altitude training [source: Simpson].
- Headache. In a mild case of altitude sickness, headache can be relieved with aspirin. If aspirin has no effect, you may be developing altitude sickness.
- Cheyne-Stokes respirations. Shallow breathing followed by not breathing and waking with a feeling of suffocation while sleeping at high altitude.
- Moderate to severe altitude sickness. Symptoms include headache, vomiting, dizziness, sleepiness, coughing and loss of balance.
- High Altitude Cerebral Edema (HACE). Swelling of brain tissue from fluid leakage
- High Altitude Pulmonary Edema (HAPE). Fluid buildup in the lungs
In addition to these serious dangers, other potentially undesirable problems can occur when training at high altitude. These include weight loss and the inability to train at sea-level intensities.
The most serious dangers of altitude training generally occur at higher altitudes (above 8,000 feet, or 2,428 meters.) We'll talk about how to train safely at altitude and explore ways to simulate altitude training at sea level in the next section.