I recently heard that 10,000 people move to Denver every month. While I do not know if this is true, I am happy that such migration is not happening in Colorado Springs. This region has too much traffic as it is, and I like my favorite trails the way they are – without too many people on them.

How do Colorado newbies, whether moving to Denver or the Springs, handle running at altitude? How long does it take to acclimate and what’s the best way to do it?

The first rule of thumb for running at altitude is to slow down. Many runners might feel fine at first, and they likely would run fine if they did not look at their watch.

Too many flat-landers try to run at their sea-level pace when they are at a higher elevation. Then one of two things happens: They get frustrated because they cannot hold the pace or they become fatigued quickly because they are working too hard.

I remember the first time I ran at high altitude. It was miserable. I was driving past Purgatory Ski Resort outside of Durango and decided to stop to run on the trails. I ran on dirt roads and trails above 9,000 feet. As I climbed, I got more and more tired until finally I had to stop. My problem was I tried to run like I ran every time I went out and did not slow my pace.

At high elevations, heart rate and breathing rate increase regardless of exercise intensity because the partial pressure of oxygen is lower, which decreases the body’s ability to transport oxygen to the working muscles. So heart rate and breathing rate increase in an attempt to provide more oxygen to the muscles. And making the heart do extra work causes one to tire quicker.

The best tactic is to train on effort instead of pace. I would not even look at the watch and instead would trust my rating of perceived exertion. Most coaches say to train easy at altitude for at least three days to let the body adjust.

A higher altitude affects runners in others ways too. Blood plasma levels decrease, resting heart rate increases and maximum heart rate is achieved quicker and with less effort.

The second rule of thumb is to hydrate. It is easier to become dehydrated at altitude because the air is drier and cooler. Runners need to hydrate not only for the typical reasons but also to help blood plasma levels return to normal and to avoid muscle cramping and headaches.

There is a difference in opinion on how long it takes to adjust to altitude. Some researchers say it only takes two weeks while others say it takes a couple of months.

Regardless of the research, it is my advice to run slow and easy for a few weeks until you do feel normal and your watch tells you that you are running at a “normal” pace roughly equivalent to your lower-altitude pace.

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Tommy Manning is a former member of the U.S. Mountain Running Team and a math teacher at Fountain Valley School. Read his columns on the first Thursday of each month in Out There.