Why Thin Air Is the Great Equaliser
Venturing into high altitudes—generally considered above 8,000 feet—means dealing with lower atmospheric pressure. While the percentage of oxygen in the air remains the same, the molecules are more spread out. With every breath, you take in less oxygen,
forcing your body to work harder to supply it to your muscles and brain. This is why even a simple walk can feel strenuous. Your body's immediate response is to breathe faster and pump your heart more rapidly to compensate. Over days and weeks, it will begin to produce more red blood cells to improve oxygen transport. This adjustment process, known as acclimatisation, is crucial, and it has very little to do with your VO2 max or how fast you can run a 10K.
Fitness Isn't a Golden Ticket
It’s a common and dangerous misconception that being a fit runner or trekker provides immunity to altitude sickness. While a strong cardiovascular base is beneficial for overall endurance, your genetic predisposition and rate of ascent are far bigger factors in how you'll handle altitude. In fact, fit individuals can sometimes be at a higher risk. Their ability to push harder and ascend faster can lead them to ignore early warning signs, moving up in elevation before their bodies have had a chance to adapt. This can turn a mild headache into a serious medical issue. Altitude doesn't care about your personal bests; it demands respect and patience from everyone.
Know the Warning Signs
Altitude sickness, or Acute Mountain Sickness (AMS), often feels like a bad hangover. Symptoms usually appear within 6 to 12 hours of reaching a new, higher altitude and can include headache, nausea, loss of appetite, fatigue, and difficulty sleeping. These are signs that you need to stop ascending and rest until they resolve. Ignoring them and continuing to climb can lead to life-threatening conditions. High-Altitude Pulmonary Edema (HAPE) involves fluid in the lungs and is marked by extreme shortness of breath (even at rest) and a persistent cough. High-Altitude Cerebral Edema (HACE) is fluid in the brain, causing confusion, loss of coordination, and severe headache. Both are medical emergencies that require immediate descent.
The Slow and Steady Strategy
The single most effective way to prevent altitude sickness is a slow, gradual ascent. A good rule is to avoid increasing your sleeping elevation by more than 1,000 to 1,600 feet per day once you are above 9,800 feet. Plan for rest days for every 3,000 feet of elevation gained. Embody the climber's mantra: "climb high, sleep low." This means you can hike to a higher point during the day but should return to a lower elevation to sleep, which significantly aids acclimatisation. Hydration is also key; the dry air at altitude causes you to lose fluid much faster. Aim to drink 3-5 litres of water daily and consider adding electrolytes. Finally, avoid alcohol, as it can dehydrate you and disrupt the acclimatisation process.
Adjust Your Pace and Expectations
For runners and trekkers, the biggest mental shift is accepting that your sea-level performance means nothing up high. You will be slower. Your heart rate will be higher for the same perceived effort. Reduce your intensity significantly for the first few days at a new altitude. If you normally run, start with a brisk walk or slow jog. Listen to your body, not your GPS watch. Pay close attention to your breathing and any emerging symptoms. Fuelling properly is also critical. Your body's preferred energy source at altitude becomes carbohydrates, so ensure your diet is rich in them to keep your energy levels stable. Don't wait until you feel thirsty or hungry to eat and drink; do so consistently throughout the day.
