The symptoms will gradually subside in a few days, but takes two weeks or so of living and riding to become adjusted to altitude. Note that occasionally symptoms do not subside in the normal interval, thus requiring oxygen and a descent. Try to bully your way up hills in thin air before then, and altitude sickness will bash you with headaches and nausea. Don't expect to set any speed records when you return to sea level, unless you're in poor shape or a smoker or something. Acclimatising to altitude simply increases the lungs' ability to take in oxygen, while the usual bottleneck is the ability of the muscle cells to take in and use that oxygen.
Muscle cells remains oblivious to altitude training.
Altitude sickness can be exacerbated by narcotics such as alcohol, morphine, babituates, and by almost all anesthetic agents. Indeed, these can cause the condition at sea level. Copyright 1999-2001 BicycleSource. All Rights Reserved.