People who’ve lived at altitude for generations, like Tibetans and Andeans, show genetic adaptations to altitude to overcome the lower barometric pressure and corresponding lower oxygen density in the air. However, the main adaptations that occur are related to immediately reduced blood plasma volume (thus raising your hematocrit level since your hemoglobin per unit of blood is higher), then over days your body releases more natural EPO to increase red blood cell production to transport more oxygen. You’ll also find your maximal heart rate is lower, even once you’re fully adapted to altitude, plus your breathing will adapt after initially leaving you more out of breath. The process is more detailed and complex, but I want to get to the practical applications for training.
Below is a high level overview which aims to prepare runners for the specifics of dealing with high altitude races, as defined below. In particular, I’ve used Leadville Trail 100-miler as an example since it’s one of the most historic ultras, and a personal favorite where I’ve enjoyed battling for wins and coached two other winners and numerous finishers.
Altitude and Side Effects
Generally, altitude can be separated into three practical bands for the effects it has on physical activity:
- Low Altitude – up to 4,000 ft (1,219m): Almost no effect on performance with Jack Daniels’ VDOT Running Calculator estimating a 7.7-second/mile slow down in a three-hour marathon at 4,000 ft due to lower oxygen uptake per breath, thus slightly lowering VO₂max. No other noticeable ill effects.
- Medium Altitude – between 4,000–8,000 ft (1,219–2,438m): More pronounced slowdown but usually no illness. Jack Daniels’ estimate for the effect on a three-hour marathon at 8,000ft is slowing 27.8 seconds/mile. Races at these altitudes can generally still be undertaken coming straight from sea level.
- High Altitude – above 8,000 ft (2,438m) especially above 10,000 ft (3,048m): Possibility of Acute Mountain Sickness (AMS) with symptoms similar to a hangover, including headache and nausea. Risks increase as altitude rises, including High Altitude Pulmonary Edema (HAPE) with a build-up of fluid on the lungs that can be very dangerous, or High Altitude Cerebral Edema (HACE) with fluid on the brain which is life threatening and requires immediate medical attention. Plus, the difficulties and dangers of exercising at altitude increase exponentially as you get higher, but even small reductions in altitude quickly help you feel better.
Data on running at really high altitude is scarce, but one of the greatest mountain runners of all time (and the course record holder at Leadville), Matt Carpenter, ran a 2:52 marathon at 14,350 ft (4,374m) and an amazing 3:22 at 17,060 ft (5,200m) to show the relative equivalent upper limits.
The City of Leadville is at 10,200 ft (3,109m) and most of the Leadville 100-miler is above that altitude, topping out at 12,600 ft (3,840m). Therefore, the advice below applies to races run in the “High Altitude” category for the majority of the race, and does not pertain to events where there are brief sections that high, such as Ultra-Trail du Mont Blanc (UTMB) which has a few passes at just over 8,000 ft.
The Ideal Way to Adapt
Unlike most training adaptations like speed work or heat training, altitude adaptation occurs mainly due to non-stop exposure to altitude and is unrelated to effort, so simply hiking or even sleeping are fine. Most sources recommend at least 12 hours a day at altitude to see a benefit, with around 12–16 hours being a common estimate. That means that altitude tents are unlikely to be of much use unless you can stay in them for longer than just while you sleep. However, bear in mind that most research in this area is either for providing altitude training benefits for sea level professional road or track racing, or for survival for mountaineers. Our niche of racing at high altitude is small enough to avoid much attention.
One key consideration is that increases in red blood cells are significantly greater above around 7–8,000 ft, so even athletes living in places like Boulder (5,328 ft) or Flagstaff (6,909 feet) will benefit significantly from going up higher. This is also borne out by the general experience of Colorado runners taking on races like Leadville and Hardrock.
The first few days at high altitude are tough on the body due to the difficulties of breathing with little positive adaptation kicking in. Two-time Leadville winner and flatlander from Texas, Liza Howard, would arrive 10–12 days pre-race in Leadville and have a headache and lack of appetite for the first couple of days, then find things gradually improving each day. Arriving anywhere from 2–6 days before the race is typically the worst option and it’s only by around day seven that your body will overcome the initial lack of adaptation. By around 28 days, the vast majority of altitude adaptations have occurred so the optimum time to arrive is 14–28 days before the race, which also fits in with tapering. Any longer will make it difficult to train hard during peak training. In fact, 2–4 weeks of light hiking to altitudes above race altitude is the perfect way to taper as well as maximize how good you’ll feel at the higher points during the race.
I don’t recommend arriving within a couple days of the race, which is common for most lower altitude events. At the least, you’ll compromise on performance, but the likelihood of some form of altitude sickness ending your race will be significantly higher than if you can arrive a week or more prior to the start. Personally, I arrive at altitudes of 9,000 ft and above two weeks out from Leadville, and hike up 14ers regularly until the final few days.
Second Best Option: Heat Training
Not everyone has over a week of spare time to spend at altitude, so the next best way to improve how you feel at altitude is through heat training. This can be done over a period of around three weeks with around 10 sessions of an hour each where you get uncomfortably hot, ideally while exercising. Wearing extra layers of clothing can simulate this, but even a hot tub or sauna will be of use.
All other modalities for preparing for altitude, such as masks or legal supplements, are likely to be marginal at best and harmful to your training at worst. However, the fitter you are the more efficient your body is at using oxygen, so it’s easier to keep your intensity sustainable at altitude. Therefore, simply getting faster and better trained for the specific terrain of your target race will definitely help.
- Altitude training is a lot of hassle and luckily isn’t essential for races below 8,000 feet.
- Staying at altitudes close to your target race’s altitude makes the biggest difference, ideally for 1-4 weeks.
- Heat training helps speed up the adaptation to altitude to compensate for less time at altitude pre-race, but the exact relationship hasn’t been quantified for this purpose. So, the one-week minimum rule for staying at altitude is still advisable.
- No matter how well you adapt to altitude it will still slow you down, so power-hiking becomes even more important and gradients that may be runnable at sea level will require hiking higher up.
- Recovery, especially sleep quality, will also be reduced at altitude, so arriving too far in advance or training hard while there may adversely affect your performance.
- There’s individual variability in how you adapt, plus factors like low iron may limit red blood cell creation, so some degree of trial and error is needed to find what works best for you.
Noakes, T. (2002) The Lore of Running p709-10
Levine, B. (2016) University of Texas Southwestern Medical Center (2016). How high-altitude training can benefit elite endurance athletes like runners and swimmers.
Salgado, R. M., White, A. C., Schneider, S. M., & Mermier, C. M. (2014). A Novel Mechanism for Cross-Adaptation between Heat and Altitude Acclimation: The Role of Heat Shock Protein 90. Physiology Journal,2014, 1-12. doi:10.1155/2014/121402
White, A., Salgado, R., Schneider, S., Loeppky, J., Astorino, T., & Mermier, C. (2014). Does Heat Acclimation Improve Exercise Capacity at Altitude? A Cross-tolerance Model. International Journal of Sports Medicine,35(12), 975-981. doi:10.1055/s-0034-1368724
Constantini, K., Wilhite, D. P., & Chapman, R. F. (2017). A Clinician Guide to Altitude Training for Optimal Endurance Exercise Performance at Sea Level. High Altitude Medicine & Biology,18(2), 93-101. doi:10.1089/ham.2017.0020