Sea Level to Altitude: How it Impacts Running

The first question most runners in Denver ask is “How are you adjusting to the altitude?” If they’re lucky my non-totally adjusted lungs leave me enough air to say…it’s altitude running is hard.

Meanwhile my Florida friends start with “are you freezing?!” and my Mid-West friends “where are you running next?”

I love having lived in so many places across the US not just for the friends, but for all the ways it’s allowed me to experience different styles of training!

In Florida, I battled the humidity and regularly ran in hot weather, so was very interested to see what it would be like to truly live and train at altitude, rather than simply swinging through on a random weekend.

While heat training, can sometimes simulate altitude. They are different. There was definitely the possibility of an uncomfortable transition period!

In this article, I’m going to help you understand how altitude running impacts athletic performance, physiological changes that occur and some tips to help you avoid common pitfalls like acute mountain sickness.

What is the difference between altitude running and high altitude training?

How high above sea level is Denver? The average is around 5,200 feet. Sea level is 0 feet or in essence land in line with or barely above the water.

Altitude training is generally considered anything over 5,000 feet.

High altitude training is 8,000 to 12,000 feet.

Very high altitude is what you hear about mountain climbers or sky racers like Kilian Jornet doing, which is 12,000 to 18,000 feet.

Why elite runners train at altitude?

Before moving to Denver, I’d heard many times of the amazing runners like Emma Sisson who chose to live and train in nearby Boulder to achieve the benefits of altitude training.

One of the principle benefits of high-altitude acclimatization or training for a long period at altitude, is that the body begins to produce more red blood cells and thus enhance oxygen capacity. This is the same EPO effect many cyclists were seeking when they began doping with it.

Many Elite athletes are now training and living over 8000 feet. Like Mammoth Lakes where Deena Kastor trains.What’s interesting is the longer we’ve lived here, the more often we’ll find new trails within just 45 minutes of us that start at 7,000 feet and I can immediately tell a difference in my breathing.

In fact, during Colorado Ragnar I started running at the highest point of the race, 10,000 feet. Even running downhill and I could tell that my breathing was different due to available oxygen!

The reason they go up higher is to maximize their sea level performance. It’s often called natural blood doping.

In fact, some have taken it up a notch with live high-train low. Research studies like The Journal of Applied Physiology showed this improved sea level performance even more than only training up high.

In this case the runner might sleep at 10,000 feet, but come down to 6,000 feet for their speed workouts. You might also hear about them sleeping in a hypoxic chamber at lower elevation to simulate lower oxygen levels from 10,000 feet.

This allows them to go harder in speed workouts and get all the benefits of living at altitude.

Once you see all the benefits listed below you’ll understand how the higher training reaps some big rewards.

Side note: altitude vs elevation – while they are scientifically slightly different, both can be used to describe the distance of an object from the ground, which is why we tend to use them interchangeably.

My first experience running at altitude was during a trip to Snowbird, Utah which was rough, also followed by a rough run at 8,000 feet in Park City…but then I miraculously busted out a 20 mile run in Boulder one trip!

Ahh the key there is a good 2500 feet difference! It can seem like what’s the big deal, once you’re up high, well it’s high. But the more altitude you gain, the more difficult.

If you’re ever wondering “how many feet above sea level am I?”, either get a super fancy trail GPS watch with an altimeter or pull out your phone, which usually has a compass function and will also tell you elevation.

So let’s dive in to the why people train at elevation, what it’s like to race vs train at altitude and a few of the tips I’ve picked up on better training with elevation changes.

Running at Altitude Explained

Why is running at altitude so different? 

Running at high altitudes decreases the amount of oxygen getting to the muscles and there’s an increased risk of dehydration.

“At 6000 feet above sea level, you exhale and perspire twice as much moisture as you do at sea level.” – From High Altitude Life.

In other words, oxygen levels at altitude decrease the farther you go up, making it harder to breathe. Altitude adaptation is what increases red cell volume and thus should increase our body’s ability to run faster.

Most of us think of altitude as specifically referring to hiking up a mountain. But altitude sickness symptoms can start as low as 6,000 feet (honestly most people trying to climb stairs in Denver really notice it!).

For climbers, the main cause of sickness is going too high, too fast without acclimating to the low oxygen level.

Runners are usually not running so quickly up a mountain that this is the cause of any issues.

But many runners will notice a change in their running when reaching the “Mile High” city of Denver. And a greater decrease in performance as they move farther in to the mountains or any location over 6,000 feet.

How Oxgyen Levels Change at Altitude

Here’s a handy chart to show the main difference of increasing altitude.

• 6,000 ft: 17% less oxygen than at sea level
• 8,000 ft: 25% less oxygen than at sea level
• 14,000 ft: about 40% less oxygen than at sea level

Photo from the new Mammoth Track, part of a project by Deena and Andrew Kastor. This is another place you’ll find many elites like Meb training!

Some claim that fit runners who are in better shape, adapt more quickly to altitude.

But science doesn’t support this idea. There just isn’t a good way to know the body time that it will take for any one person to adapt.

For example, while I run 150 miles a month, David had been on a hiatus from training and yet I was the one who felt the impacts of altitude on every single run and especially when we went out for hikes with a gain of 1,700 feet or more.

What does less oxygen mean for training?

Luckily our bodies are miraculous machines, that begin adapting to our surroundings without us needing to think about it. So here’s what it’s doing to try and make up for the decreasing oxygen levels:

1. You start to breath faster to initially increase your oxygen levels.
2. You urinate more frequently as your kidneys try to keep the body balanced (it’s like a diuretic)
3. Your body increases red cells in your blood to better carry more oxygen
4. Heart rate and blood pressure increase in an attempt to push more oxygen
5. Blood thickens also making your heart work harder
6. A good night’s sleep often becomes harder with more wakefulness

As you continue to increase altitude, the body also begins to battle the decreased outside air pressure, which adds to the feeling that it’s hard to breathe and you feel more fatigued than normal on your run.

According to Greg McMillan, over 7,000 feet you can expect an easy run to be up to 30 seconds slower per mile to achieve the same easy level of effort.

How running at altitude effects the body and your pace! #runchat Share on X

How might you feel running at altitude?

Your body doing all of this work is part of what causes many people to feel less than fantastic when they first get to altitude…also known as altitude sickness, but for many it’s actually just dehydration!

• Headache
• Harder to breathe (harder and harder the higher you go)
• Runs feel harder (because you can’t breathe)
• Nausea
• Possible sleep disruptions
• Often a major decrease in appetite, which you need to overcome to fuel your runs

All of these are key reasons why we say to drink lots of water! You have to stay on top of hydration to protect your health and performance.

Above, Desi on a training run at elevation.

It seems that the benefits can last for up to 2-3 months after living at altitude. In order to get both the oxygen benefits and work on speed, you’ll notice that many elites do periodized training from high to low altitude.

Or a newer strategy of “Live High, Train Low” where athletes sleep at high altitude, but come down lower daily for training sessions.

9 Tips for Running At Altitude

There is a lot of science you can read on this, but here are some plain English tips for the common runner who is simply ready to enjoy a run on vacation. Remember that for sedentary people, this might not be the time to try your first run.

1. Drink large amounts of water!

A hilarious rhyme I heard “Before you hit the trail, best your urine be pale.”

In other words, you need to drink more water than you’re used to drinking. It’s very easy to become dehydrated because you are breathing out more so you lose water through respiration and the air is very dry so your sweat dries quickly potentially not triggering your normal urge to drink.

2. Go Quickly

Go for a run as soon as you can upon arrival. Altitude sickness often sets in a day or two after arrival.

Thus, if you can get out the door quickly you might enjoy your first run taking in the scenery before your body starts to notice what’s changed.

After that for the first couple of days, try keeping everything a bit more low key. Enjoy your hikes, walks and strength training. But give the body time to really warm up to this change.

3. Avoid Alcohol and Caffeine

The dehydration will slow your adjustment to altitude as the body again is expelling more water and further stressing the kidneys. It also leads to headaches while running and nausea while running!

Now, this tip alone has burst a lot of skier bubbles. So I’m going to say sip wisely, and really focus on extra hydration if you are going to partake after your sweat sessions.

Same goes with your morning cup of joe. Just remember you need to offset the extra water loss.

4. Slower Paces

This isn’t the time to force a speed work session, instead take advantage of the great views and enjoy a leisurely paced run. Your heart rate will likely be higher as your body works harder to get oxygen.

You won’t have a normal breathing response and so again, your brain will tell you this is harder. That’s because it truly is harder.

5. Maintain Iron Levels

Your body needs more iron as it creates more red blood cells. Be sure to eat iron-rich foods, like red meat and greens, along with Vitamin C which helps with absorption.

I actually started taking an iron supplement when we moved to Denver, to help keep my levels up.

6. Increase Carbohydrate Intake

You’ll want carbs to be at least 70% of total calories if you’re doing a longer training run.

This is because carbohydrates require less oxygen for the body to process and when you first arrive at higher altitude your body will use more carbohydrates for fuel. Like anything, over time you will adapt back to burning more fat for fuel on your easy days.

7. Plan Time to Acclimatize

If you’re planning a destination race at altitude whether that’s Western States or just a fun Leadville trail run, try visiting at least 2 or 3 times prior to the race for a weekend.

It’s not the same as training there, but it can certainly help.

Additionally, as noted above you want to plan on either racing almost as soon as you arrive or giving yourself a good week or two prior to the race.

8. Consider Walk Breaks

Even if they are not part of your normal routine, a few pauses throughout the run may allow you to continue with less trouble breathing.

Run/walk has worked for ages and continues to have benefits for all kinds of endurance race scenarios. There’s a reason that ultramarathon runners embrace it.

9. Rhodiola

Try using something like Rhodiola! It happens to be in the Vega Pre-Workout that I use, so I didn’t realize I was getting the benefit until I was doing some research and found this:

Rhodiola is widely distributed at high altitudes in mountainous regions over the world. It is commonly used in traditional medicine in Asia for stimulating the nervous system, enhancing work and exercise performance, eliminating fatigue and preventing mountain sickness.

What Have I Noticed Running at Altitude?

I know this is what everyone is dying to know…so let’s break it down.

We moved to Denver from sea level around December 1st and I definitely noticed that it was harder for me to keep my heart rate down during runs, which meant going slower to continue doing Low Heart Rate training.

Over the following 3 months, I was traveling almost every 3 to 4 weeks, which means I have yet to have a long consecutive period of training in Denver. However, I do know that I start to adjust during each period because when I leave and come back I am immediately feeling that it’s harder to breathe again. Having talked to a lot of runners here, many of them said it was at least a year before they really felt like they could pick their pace back up and felt strong running.

*** UPDATE**
We’ve now been in Denver for 5 years and I can truly tell the difference. I was injured for most of 2017 which knocked my mileage way off, but 2018 was great!

Post surgery, I had to climb back to my old endurance, but then I went to a couple races.

1. Going down to sea level made my breathing feel so good, that it was absolutely easier to run faster.
2. I still train a little slower at altitude because I watch my HR, but that is slowly improving too.
3. I still notice when we go from 5,500 feet in Denver to a trail that starts at 7,000 feet.
4. I’ve learned that training fast when you get to sea level is a great way to take advantage of both.
5. When I return from traveling for over a week, I still notice a couple runs where my breathing has to readjust.

Overall I love living here, so the training here is great, even if I feel a little slower some days!

Have you ever run at altitude?

Ever experienced altitude sickness?

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