Altitude: The Endurance Athlete’s Tricky Friend

By Pat – October 3, 2013

I’ve spent the last three summers in Colorado, escaping the Texas heat in order to get the most out of my training.  Endurance athletes have long used altitude training as a tool to gain an edge on the competition.  While I’m no physician, I have learned about altitude training through experience and I believe that, when used prudently, it can make a significant difference in an athlete’s performance.  Keep in mind, though, that it’s not all puppies and rainbows.  Incorporating training and racing can be tricky because of the way the body adapts to changes in elevation.

It’s important to understand how altitude affects the body.  People talk about “thin air.”  Air is always made up of 21 percent oxygen, whether at sea level or the top of a mountain.  The difference is the atmospheric pressure.  The higher up, the lower the pressure.  Think about diving to the bottom of a swimming pool: You feel more pressure at the deepest point because there is a greater weight of water directly above you.  The higher the altitude, the lower the pressure, which results in the molecules that make up air being spaced further apart.  Higher pressure (as in a scuba tank) compresses the molecules.  Therefore, at higher elevations—and even though oxygen still composes 21 percent of air—the atmospheric pressure is low and air molecules are farther apart; therefore, when taking in a breath of air, you get fewer oxygen molecules in each lungful—and we call that “thin air.”

Why does this matter to the athlete?  This is because, with each breath, the body has less oxygen to use when exercising at a higher altitude.  The more aerobic the exercise (like distance events), the greater the effect becomes.  I’ve read that the medical world recognizes performance decreases above 4,000 feet above sea level (Austin sits at about 500 feet).  So, if exercising at higher altitudes than accustomed is detrimental to performance, why do many endurance athletes train at higher altitudes?  It’s because the human body is smart and will adapt to the decreased oxygen.  The primary way the body acclimates is by creating more red blood cells, which transport oxygen from the lungs to the muscles.  Some research also suggests adaptation may additionally increase the amount of capillaries (tiny blood vessels) in muscles.  Therefore, more oxygen is carried to the muscles through better plumbing.

If this adaptation is so great, then why did I use the term “tricky”?  Altitude training is not as straightforward as it might sound.  Every athlete is different, and experiences with adaptation and training vary.  These tips are things that I have found—through personal experience, research, and learning—to work for me.


The human body needs approximately four to eight weeks for physiological adaptations to altitude to occur.  They don’t all happen at once; rather, it’s a gradual process.  When you go to Colorado for a week’s vacation, your body doesn’t make any real adaptations. Yes, you feel better when you get home, but that’s because your body is getting more air; there’s no lasting effect.  Take a look at how your body adapts over time:

0-3 days: This is usually the hardest period, and the time most people will experience altitude sickness.  Train, but keep it easy and short.  Focus on extra rest and hydration.

3-14 days: Athletes tend to feel better, but the body isn’t ready to hit the training hard yet.  Add in volume, but keep the effort easy, easy, easy.  Even when feeling good, don’t push the speed or you could find yourself in bed, exhausted.  I do longer bike rides and runs at a conversational pace.

14 days – 1 month: At this point, intensity can be added into training if the athlete feels well.  Don’t go hard every day; keep the volume high, but there should be a lot of easy training to compliment the hard sessions.

1-2 months: Athletes are pretty much fully adapted, and training can commence ALMOST as at sea level.  You will always need to monitor your body at altitude, however.  Even though you feel better, it’s still too easy to push yourself into a hole of exhaustion.



My running pace starts around 30 sec/mile slower in Boulder than in Austin.  As I adapt, that gap gets smaller, but I can never run quite as fast at altitude.  It’s important to keep your muscles able to fire at their sea level rate or you can lose your speed, so many pros find slight downhills—not steep enough for pounding—and run workouts that get leg turnover up.  Also, many professionals utilize treadmill workouts because it’s easier than keeping turnover high on the road.


Swimming is much harder at altitude than at sea level for two reasons.  First, it’s easy to simply breathe harder when the air is thin while running or cycling but with swimming, breathing can only occur as you rotate with each stroke.  Therefore, if you want to breathe more often, you have to increase your stroke rate …and that makes you breathe even harder, which creates a downward spiral.  Second, flip-turns require you to hold your breath going into the wall and then hold it again as you glide off the wall before surfacing.  As a result, you end up holding your breath for several seconds. This puts you into an even deeper oxygen debt.  I find it takes me several weeks at altitude before I can swim a workout properly.


Racing at a lower elevation is the best part of altitude training.  I feel like I have an extra lung when I race low, but there are a couple of factors that make the difference between racing well and falling flat.  Again, it all comes back to timing:  Race within a week of coming down or after four weeks, but NOT INBETWEEN.

Within Week 1:  You will feel the best in your first week down, so it’s advantageous to arrive a handful of days before your race, do your last few easy jogs, and then race.

After Week 4: The other good sweet spot is to descend four weeks before your race, which allows a couple of weeks of hard training with lots of speed work plus a taper and time to absorb that hard work.  Yes, you will have lost altitude adaptations by race day, but you may still be faster thanks to putting in a hard, fast training block and reaping the benefits.

Weeks 2 – 4:  If you come down two to three weeks early, you will probably still have some real workouts before your race. The problem is, you’ll feel so good that it’s easy to push too hard in those last swims, bikes, and runs, which means you’re still training rather than sharpening.  Also, you will have lost most of your adaptation in that time, so you’ll show up tired from training too hard and without your altitude benefit!

The Details

  • Other factors are critical to how you function at altitude. Keep in mind:
  • You will need more rest and recovery time.
  • The effects of harder workouts can linger longer in your body.
  • Chronic fatigue can build up quickly if you don’t get enough rest and sleep.
  • Dehydrated occurs much more quickly at altitude.
  • The body can become depleted of vitamins; many experts advise paying attention to iron intake, especially for athletes who don’t eat red meat (always check with a doctor before starting any kind of iron supplementation).

Keep this information in mind, and you can use altitude training to make adaptations and realize your best racing.


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