Altitude Sickness and Trail Running: How to Prepare for High-Altitude Races in China
Editor's Note
This guide was prepared in collaboration with our partner RunEast, a China-based platform dedicated to helping international runners discover, understand and register for some of the country's most spectacular trail races. Drawing on their local expertise and experience of high-altitude events, this guide is to help overseas runners prepare for racing in thin air safely and confidently.
For additional practical information and the original guide from RunEast, visit: https://runeast.app/guides/altitude-sickness-guide
China is home to some of the highest trail races on the planet, from the FUGA Glacier Extreme Gongga 100 in Sichuan to the Shangri-La Trail in Yunnan. Many courses start at 2,000 – 2,500 metres and climb well above 4,000 metres, crossing the edges of the Sichuan and Yunnan plateaus and the mountain ranges of Qinghai and Tibet. The scenery is extraordinary, but so is the challenge: thin air, low atmospheric pressure and sudden temperature swings affect every runner, however fit.
That is why altitude sickness is the single most important thing to understand before you race at altitude in China. The good news is that it can be managed. With the right acclimatisation strategy, sensible pre-race habits and a clear plan for race day, most runners can enjoy these spectacular events safely.
This guide explains what acute mountain sickness (AMS) is, how to recognise the symptoms, how to acclimatise for a high-altitude race, and exactly what to do if altitude sickness hits mid-race.
What Is Altitude Sickness (Acute Mountain Sickness)?
Acute mountain sickness (AMS), commonly called altitude sickness, is the body's reaction to arriving quickly at high altitude. Above around 3,000 metres, the lower air pressure means each breath delivers less oxygen. Your body starts adjusting straight away, and the discomfort you feel during that adjustment is AMS.
Crucially, almost everyone experiences some degree of altitude sickness. It does not mean you are unfit or poorly trained, and elite athletes are not immune. Severity varies from person to person and from trip to trip, so past experience is no guarantee.
For trail runners, the aim is not to avoid AMS completely. It is to manage it well enough to race safely, and to recognise the point at which it becomes dangerous.
Why Are Trail Runners at Risk?
Trail runners often travel long distances, arrive close to race day and then push their bodies hard at altitude, which is exactly the combination that makes AMS more likely. Long ultra-distance efforts also mean many hours of exposure, often overnight, when temperatures drop and fatigue builds.
Altitude Sickness Symptoms: Mild, Moderate and Severe
Knowing the warning signs is the most important safety skill you can bring to a high-altitude race.
| Severity | Typical symptoms | What to do |
|---|---|---|
| Mild | Headache, nausea, light-headedness, shortness of breath, poor sleep, reduced appetite | Rest, warm fluids, avoid exertion. Oxygen or medication only under medical supervision. |
| Moderate | Bluish lips (cyanosis), drowsiness or agitation, worsening breathlessness, intensifying headache | Stop racing. Descend and seek medical attention. |
| Severe | Prolonged severe headache, confusion, hallucinations, loss of consciousness, persistent dry cough with pink, frothy sputum | Medical emergency. Descend immediately with assistance and get urgent medical care. |
HAPE and HACE: The Dangerous Forms of Altitude Sickness
If AMS progresses, it can develop into High Altitude Pulmonary Edema (HAPE), fluid on the lungs, or High Altitude Cerebral Edema (HACE), swelling of the brain. Both are life-threatening.
The rule is simple: if you have moderate or worse symptoms, stop racing, descend and seek medical attention. No finish line is worth the risk.
How to Acclimatise for a High-Altitude Trail Race
According to Professor Bärtsch, a leading researcher in altitude sports medicine, athletic performance begins to change from as little as 650 metres above sea level. For training or competing above 2,600 metres, he recommends 3–4 days of rest before reaching race altitude.
In practice, that means acclimatisation should be part of your race plan from the moment you book your trip.
Arrive Early: 2–3 Weeks Is Ideal
The ideal acclimatisation window is two to three weeks before your race. That gives your body time to adapt to lower oxygen levels and lets you explore the region at an easy pace.
If that is not realistic, aim to reach the race start location at least two to three days before the race. Use that time to see how your body responds, and adjust your race plan if needed.
Climb High, Sleep Low
The most effective acclimatisation method is “climb high, sleep low”: hike or train at higher altitude during the day, then return to a lower altitude to sleep. Your body gets the stimulus to adapt without the strain of a night spent at your highest point.
Consider Altitude Simulation at Home
If your health allows, hypoxic (altitude simulation) training at home before you travel may help your body start adapting. It is not a substitute for time at altitude, but it can give you a head start.
Adjust Your Expectations
Your aerobic capacity drops at altitude, so running slower than usual is normal. Base your pacing on effort, not your sea-level splits, and treat your finish time as secondary to finishing safely.
Pack All Mandatory Gear
Mountain weather can change in minutes, from sunshine to hail and near-zero visibility. Bring every item on the mandatory kit list, even if the forecast looks good.
Pre-Race Guide: 5 Ways to Reduce Your Risk of Altitude Sickness
The days between arrival and the start line are when good habits make the biggest difference.
1. Drink More Than You Think You Need
Aim for 3–4 litres of water per day, at least 1.5 times your normal intake. Carry a thermos and sip warm water frequently. Research suggests that staying properly hydrated alone can reduce the incidence of AMS by more than 40%.
2. Eat Plenty of Carbohydrates, but Don't Overeat
Increase your carbohydrate intake with rice, noodles and energy gels. Carbohydrates produce more carbon dioxide when metabolised, which stimulates breathing and helps improve blood oxygenation. Stop eating when you are about 70% full, as a heavy stomach makes altitude discomfort worse.
3. Stay Warm, Especially Your Head
Wear a hat: wind at altitude chills you quickly, and a cold head can trigger headaches. For the first two days at race altitude, avoid washing your hair or taking cold showers. Catching a chill raises the risk of respiratory illness, which in turn increases the risk of AMS.
4. Resist the Urge to Run on Arrival Day
After a long journey to spectacular mountains, the temptation to head straight out is huge. Limit yourself to a gentle walk and some photos. Save the big runs and hikes for after the race: any session over 15km before the start is more likely to hurt your race than help it.
5. Sleep Smarter at Altitude
- Go to bed about an hour later than usual. Going to bed too early at altitude often leads to waking in the night.
- Avoid alcohol, which suppresses your breathing reflex, and coffee, which is a diuretic, before the race.
- If you suffer severe insomnia, speak to a medical professional about short-term sleep aids rather than self-medicating.
What to Do If Altitude Sickness Hits Mid-Race
Even with perfect preparation, symptoms can appear during the race. Here is how to respond.
Slow Down Immediately
If your headache worsens or nausea builds, switch to a power hike. Do not try to push through. Reducing your effort is often enough to stabilise mild symptoms.
Keep Eating and Drinking on Schedule
Take an energy gel or salt tablet every 45 minutes and drink sports drink at every aid station. Under-fuelling and dehydration make altitude symptoms worse, and your appetite may drop just when you need fuel most.
Use the Medical Checkpoints
Well-organised high-altitude races provide medical staff, oxygen cylinders, pulse oximeters (to measure blood oxygen) and emergency supplies. If you feel unwell, stop and get checked. That is what they are there for.
Don't Tough It Out
Many high-altitude courses have descent routes at regular intervals. If medical staff advise you to drop out, follow their advice. Descending is not a failure; it is a rational and courageous decision that lets you come back and race another day.
Frequently Asked Questions About Altitude Sickness and Trail Running
At what altitude does altitude sickness start?
Acute mountain sickness typically starts above around 3,000 metres, although athletic performance can begin to change from as low as 650 metres. Many trail races in China start at 2,000–2,500 metres and climb above 4,000 metres.
What are the first signs of altitude sickness?
The most common early symptoms are headache, nausea, light-headedness, shortness of breath, poor sleep and reduced appetite. These are classed as mild AMS.
How many days should I acclimatise before a high-altitude race?
Ideally two to three weeks. At a minimum, arrive at the race start location at least two to three days before the race. For racing above 2,600 metres, Professor Bärtsch recommends 3–4 days of rest at altitude.
Can fit runners get altitude sickness?
Yes. Almost everyone experiences some degree of altitude sickness, regardless of fitness. Being fit does not protect you, and pushing hard can make symptoms worse.
Does drinking water prevent altitude sickness?
Hydration does not prevent AMS entirely, but research suggests staying properly hydrated can reduce its incidence by more than 40%. Aim for 3–4 litres a day at altitude.
When should I stop running because of altitude sickness?
Stop racing, descend and seek medical attention if you have moderate or severe symptoms, such as bluish lips, drowsiness or agitation, worsening breathlessness, confusion or a persistent cough. These can signal HAPE or HACE, which are life-threatening.
Final Thoughts
High-altitude trail races in China are among the most rewarding experiences in the sport, from the glaciers and alpine terrain of the Gongga 100 in Sichuan to the Tibetan landscapes of the Shangri-La Trail in Yunnan. Altitude sickness is part of that adventure, but it does not have to define it.
Still choosing your race or planning your trip? Read our complete guide to trail running in China for international runners for regions, races, registration and practical travel tips.
Arrive early, acclimatise patiently, look after the basics of hydration, food, warmth and sleep, and know when to slow down or step off the course. Respect the mountains, listen to your body and you will give yourself the best chance of reaching the finish line safely.
This guide is for general information only and is not medical advice. If you have a medical condition, or are unsure whether high-altitude racing is right for you, consult a doctor before you travel.
About this guide
This article was prepared in collaboration with our partner RunEast, a China-based platform dedicated to helping international runners discover, understand and register for the country's most spectacular trail races. Their local knowledge and English-language resources make racing in China far more accessible for overseas runners. Read the original guide here: https://runeast.app/guides/altitude-sickness-guide
