Altitude and Performance

March 15 2024

It is desirable for many athletes to have access to altitude for performance enhancement. This may seem relatively intuitive if you’ve ever experienced how difficult altitude can make everyday activities. It's like sucking the air out of the room and strapping on ankle weights- that’s got to be good for exercise performance, right? While we agree that altitude can influence performance, the mechanism is quite complex and depends on the length of the stay, how high you go, and whether you train up there. It is a muddled means for performance enhancement, and often depends on the activity.

Starting from the beginning- oxygen gas is an important substrate for high-energy generating reactions within your body. Although we are able to make some ATP (energy that gets converted to work in your body) without oxygen, these pathways are not sustainable standalone. For this reason, unlike fermenting or deep sea bacteria, we need to breathe. Gasses (like O2) in the air are constantly bouncing around randomly, running into each other and surfaces. This gas- bumper-car-dance exerts pressure. Pressure likes to move downhill. Essentially, at altitude, there is not less oxygen per se, but the partial pressure of oxygen gas is quite low as compared to sea level. This low pressure at altitude narrows the pressure difference to your lungs, making it more difficult for oxygen to transfer from the air to the lungs, and then into the blood. For this reason, many of the exercise related effects of altitude have to do with respiratory and circulatory systems, important for delivering oxygen to tissues and working muscles and greatly affecting aerobic performance.

Acute Exercise

At Altitude If you arrive at altitude from sea level on a vacation or to compete in an event, like, say the Leadville 100, not only will we praise your gusto, but your body will experience changes in response to physiological stress. 

Hydration Consideration

When you arrive at altitude, your ventilation rate will increase due to enhanced catecholamine release (what you think of as adrenaline). This enhances the respiratory fluid loss. For this reason and in concert with increased urinary output, plasma volume significantly declines immediately upon arrival to altitude. It is in turn important to diligently hydrate before, during and after exercise to maintain hydration at altitude and all of the benefits which accompany it. 

Circulatory Considerations (heart, blood, lungs)

Your circulatory system operates to deliver oxygen to working tissues. Assuming your ascent to altitude is fairly rapid, your body will compensate for the low pressure of oxygen in the air to attempt to balance this out and preserve delivery to tissues. Your brain will release adrenaline (from the sympathetic nervous system) to increase heart rate and ventilation to speed up the movement of blood through the pulmonary system to the working muscles. For any given submaximal exercise intensity then, your heart rate will be higher to enhance cardiac output in compensation of less available oxygen. What’s more, the aforementioned fluid loss leads to an initial decline in plasma volume. Despite having a negative impact on the hydration mechanism, this plasma volume loss acutely raises the concentration of hemoglobin- the oxygen shuttle- to initially maintain O2 delivery before longer term mechanisms can kick in and generate more blood cells and hemoglobin (to be discussed). Overall, your heart is working much harder when acutely exercising at altitude. 

VO2 and VO2 Max

Hold on to your britches here. VO2 refers to the volume of oxygen delivery to tissues. In turn, VO2 max is the maximum volume of oxygen any individual can deliver to the body going all out. These concepts are a function of cardiac output (liters of blood delivered per minute) and tissue oxygen delivery (the difference in O2 between arteries and veins) and are great measures of endurance capacity as they can allude to aerobic efficiency. Upon initial exposure to altitude, VO2max declines as there is less available oxygen, and the body has not yet been able to compensate for this loss. For this reason, if you are competing at an event at altitude without acclimatization, your exercise capacity will drop. 

Exercise intensity refers to the percentage of VO2 max you are working at. Interestingly, VO2 delivery to muscles at submaximal exercise does not change. Basically, your muscles require the same volume of oxygen for any given effort no matter what. However, because VO2 max declines with acute altitude exposure, VO2 stays the same. Therefore exercise intensity increases as you use a greater percentage of your VO2 capacity for a given workload. This is why exercise at altitude feels difficult (intensity is rising) but is not hormetic in the context of VO2: you are not able to push yourself as hard as you could at sea level. Put another way, the same exercise intensity at sea level will feel a lot more difficult at altitude (without acclimatization) as the ceiling for VO2 is lower. 

Chronic Exercise at altitude: Training Adaptations?

When you have been at altitude for some time, physiological adaptations ensue. So what happens when you stay high?

Circulatory Considerations (heart, blood, lungs)
When you acclimatize to altitude (after a few weeks), your resting heart rate drops as compared to the acute condition, tugging your heart toward homeostasis. Interestingly, with prolonged exposure to altitude, the volume of blood your heart can eject to the body in any given beat- known as stroke volume- declines. This is due to loss of plasma volume and increased hematocrit, and is a variable that can affect your cardiac output in exercise. For this reason, hydration continues to be an important management strategy at altitude.

Of chief concern to athletics, upon initial arrival to altitude, there is a detectable increase in Erythropoietin (EPO). EPO is a hormone from the kidneys that stimulates the production of new red blood cells. Despite the initial spike in EPO, it takes many weeks at altitude to observe a significant change in red blood cell mass, and thus, oxygen carrying capacity or the net saturation of oxygen onto hemoglobin. This is the effect most athletes chase when engaging in altitude training. 

VO2 and VO2 Max
Upon altitude acclimation, there is mixed data regarding the changes that occur in VO2 max. Some studies find that VO2 max increases in athletes, and others find no difference in VO2 max with altitude acclimatization as compared to sea level acclimated athletes. This could be due to genetic differences in altitude tolerance. Alternatively, these inconsistent results could be explained by a “detraining effect”- essentially altitude makes training at higher intensities more difficult, rendering the achievement of major changes in one’s VO2 max more difficult. For this reason VO2 max changes in response to altitude is still highly researched and debated. That said, studies have shown performance enhancement and better outcomes in races at sea level following altitude acclimation. 

Training Paradigm

The scientific community has found the Live High Train Low (LHTL) paradigm to be the most accepted form of altitude training. In theory, living at altitude can provide positive cardiovascular adaptations such as increased red blood cell mass and oxygen carrying capacity, while training at lower altitude allows training intensity to remain high. Despite the backing of LHTL, the most important aspect of training is specificity. Specificity refers to training for events or conditions that you will be competing or consistently recreating within. For this reason, tailor your fitness to your lifestyle and event routine. We aren’t telling you not to try it, we are just saying if you live, train, sleep, and compete by the sea, there is no need to find tickets to the Colorado Rockies. That is unless you want to come see us. 

Cheat Sheet

In Tanzania, on Kilimanjaro they use the Swahili term, pole pole, which means slowly slowly. The slow approach to hiking at high altitude allows the body time to acclimate, but it is not just on the mountain you want to be cautious of speed. Anything which takes you from low altitude to high altitude quickly can rock your system - the speed of ascent is what can do you in with altitude. So if headed to a spot like the mountains in Colorado, it’s wise to fly to Denver and spend a day at 5,000 ft instead of jetting up to 9,000 or 10,000 right off the bat. The more time you can give your body to acclimate at each elevation gain the better chance you have at feeling good up high. Don’t be fooled, altitude sickness can happen at lower altitudes than you would think.

Some preventive care tips include:

Staying hydrated (Everyday Drink Mix or daily hydration recipe, and if active: our sport mix)


Don’t let the loss of appetite that can happen at altitude take its toll, be sure to get your calories in, some people’s guts can be more sensitive at elevation so try to start with simple meals.

The loss of appetite that can happen up high and particularly when exercising can make you susceptible to bonking, so be sure to back a mix of foods as what you thought might be appealing might change once you lose your appetite, or try a liquid fuel like High-Carb Drink Mix as an easy way to get energy in.

Reduce your intake of alcohol

Wear your sunscreen, it’s easy to get burnt up high and the impacts of the sun can take a toll on performance

If not competing, and headed to something like Kilimanjaro talk to your travel doctor about meds for high altitude.

Head here for information on high altitude sickness and treatments.

To find out more and read the studies referenced, check out all of our sources and studies below. 

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