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It takes time to adjust to changes in altitude

Question: I am going to Colorado for six days to ski. I'll be on the slopes for five to six hours a day. I stay in good shape by exercising on Nautilus machines three times a week and playing tennis most other days. Can I do anything to condition myself for the change in altitude from my home in Florida? Answer: No, only time will adjust your body to the altitude. Here's why:

At higher altitudes you tire more quickly, particularly when you do something as strenuous as skiing. The reason is that as altitude increases, the oxygen and other molecules in the air spread out and away from each other. This is what causes balloons to burst as they rise higher in the atmosphere.

As a result, the higher up you go, the less oxygen there is in a given volume of air, and the less you take in with each breath. In addition, this decrease in oxygen triggers a temporary disruption in your oxygen transport system _ that is, not only do you take in less oxygen, but what you do inspire has difficulty getting from your lungs to your muscle tissue.

Muscle tissue needs a rich supply of inspired oxygen to maintain peak performance for any length of time. At the 1968 Mexico City Olympics (altitude 7,800 feet), for instance, there was a steady increase in the longer running and swimming times _ ranging from 3 percent for those events lasting about 4 minutes to 8 percent for events taking approximately 1 hour. This occurred even after the athletes were more or less adjusted to the higher altitude.

However, explosive activities such as 100- to 400-meter runs, where inspired oxygen is not needed for energy, are not affected. Also, strength does not decrease. Some evidence suggests that strength might actually increase at high altitudes.

Therefore, when you first hit the slopes you will probably experience a 10 to 15 percent reduction in your energy _ although people differ widely in how they respond to changes in altitude. But your oxygen transport system will soon adjust, and you should be fine in a day or so. Some people feel fully acclimatized in two days, but others may take a week or longer.

One precaution. With altitude there is a loss of plasma volume, the liquid part of the blood. This is one reason oxygen does not move as well through the body. So drink plenty of water _ even when you are not thirsty.

Some swimmers get faster as they get older

Question: Why is it that swimmers in their 30s and 40s _ even 50s, in my case _ are swimming faster than we did as high school and college competitors? I thought we were supposed to get worse as we get older.

Answer: Not all swimmers are able to swim faster. National and international competitive records show that swimmers are at their best between about 18 and 25 years of age, although there are many exceptions. After about age 25, the average speed for the record performances begins to decline _ in masters competition in the 50-yard and 200-yard freestyle events, for instance, this amounts to about 1 percent per year for both men and women up to about age 85.

This downturn, of course, parallels age-related declines in our endurance, strength, reaction time and flexibility. The speed of these changes can be slowed quite a bit with conditioning, good nutrition, and by generally living a healthy lifestyle. But they cannot be reversed.

It is true, however, that some masters swimmers are able to achieve personal-best performances well into middle age. Exactly why is not known. It is probably because they have experienced a minimal decline in their physiological capacity while taking advantage of improvements in coaching, swimming technique, training methods (particularly the use of interval training and weight training), and swimming facilities that are far better designed to minimize drag.