How to Prepare for a Trail Race at Altitude

Quick answer: To prepare for a trail race at altitude, arrive early if you can, go up gradually, and keep your first 48 hours easy. The CDC says unacclimatized travelers sleeping at 2,450 m (8,000 ft) or higher are at risk of acute mountain sickness, advises avoiding alcohol and doing only mild exercise for the first 48 hours at altitude, and says never to go up to sleep higher while you have symptoms. Plan a slower pace for race day, and talk to a doctor before the trip if you have health concerns.

What changes at altitude

There is less oxygen in each breath at altitude, so the same pace feels harder. That is why effort, not pace, is the better guide on a high race course. Our uphill running guide covers when to run and when to hike.

Know the signs of acute mountain sickness

According to the CDC, acute mountain sickness (AMS) feels like a hangover. Headache is the main symptom, usually with at least one of: loss of appetite, dizziness, fatigue, nausea or, sometimes, vomiting. It typically starts 2 to 12 hours after arriving.

• The CDC says: never go up to sleep at a higher altitude while you have symptoms, however minor.
• Descend if symptoms get worse despite rest at the same elevation.

How to acclimatize before race day

The CDC Yellow Book acclimatization checklist includes:

• Ascend gradually. Avoid going directly from low altitude (below 1,200 m or 4,000 ft) to above 2,750 m (9,000 ft) in one day.
• Above 3,000 m (9,850 ft), increase your sleeping altitude by no more than 500 m (1,600 ft) per day, with an extra acclimatization day for every additional 1,000 m (3,300 ft).
• Avoid alcohol for the first 48 hours at high altitude.
• Do only mild exercise for the first 48 hours at altitude.
• If you drink caffeine regularly, keep drinking it, so a withdrawal headache is not confused with an altitude headache.
• A high-altitude stay (above 2,750 m) of at least 2 nights within 14 days before the trip helps; closer to the trip is better.

The checklist also mentions medication to speed acclimatization when a fast ascent cannot be avoided. That is a decision to make with a doctor.

Race day at altitude

• Run by effort and expect a slower pace, especially on climbs.
• Plan water and fuel as carefully as at sea level; see how much water to carry and the fuel guide.
• Mountain weather changes fast. Carry the layers on the race's required gear list; see the race checklist and how to layer for the cold.
• Protect yourself from the sun on exposed ground; see sun protection for trail runners.

FAQ

How many days early should I arrive?

The CDC gives guidance for sleeping altitude rather than a set number of days for racing. Use the checklist above, and keep the first 48 hours easy.

Can I still race if I have a headache?

Headache is the main symptom of AMS. Follow the CDC advice: do not go higher while you have symptoms, and descend if they get worse. Get medical advice.

Source: CDC Yellow Book, high-altitude travel and altitude illness. This guide is general information, not medical advice.