As hikers gain experience, they often want to tackle more ambitious summits. However, the effects of altitude on the body should never be underestimated. To properly prepare for a high-mountain outing, a few precautions are essential. Cimalp shares its top tips for high-altitude hiking.
The effects of altitude on the body
Thinner air
A high-altitude hike has significant effects on the body. Indeed, the higher you climb, the lower the atmospheric pressure drops. Blood oxygenation decreases and the body enters a state of hypoxia. You may then experience shortness of breath and reduced physical performance.
Above 2,500 metres, you may also experience the first symptoms of Acute Mountain Sickness (AMS). When the body does not adapt quickly enough to altitude, headaches, nausea, insomnia or loss of appetite can occur.
Lower temperatures
At high altitude, temperatures drop by an average of 6°C for every 1,000 metres of elevation gain. It can get cold, even in the height of summer. Cold conditions are felt even more acutely at night, when temperature drops compared to daytime are often substantial. The chill is further amplified by wind, which can be intense on exposed sections. The wind chill effect can significantly accelerate body heat loss.
Solar radiation and UV
In the mountains, solar radiation is far stronger. UV intensity increases by about 10% for every 1,000 metres of elevation. Glare from snow or light-coloured rock further amplifies exposure. As a result, you risk sunburn, sunstroke or snow blindness.
Accelerated dehydration
Hiking at high altitude causes a drop in air humidity. This phenomenon is linked to hygrometry. The higher you climb, the more air humidity decreases. This dry air leads to increased water loss through breathing and sweating. Even without visible perspiration, you lose a significant amount of fluid and risk accelerated dehydration.
Other effects of altitude
In addition to these factors, high-altitude hiking can have other effects on the body. You may notice a decrease in appetite, sleep disturbances or increased fatigue due to slower muscle recovery.
The acclimatisation phase at altitude
Understanding acclimatisation
Acclimatisation during high-altitude hiking is crucial. The body needs to adapt to the lack of oxygen. To compensate, it must increase your breathing and heart rate, and produce more red blood cells. This process takes time.
Ascending gradually
To give your body time to adapt to the altitude, ascending gradually is essential. Above 2,500 metres, following the “Climb high, sleep low” rule is recommended. This means climbing during the day, but sleeping no more than 300 to 500 metres higher than the previous night.
Overexertion is also strongly discouraged. Acclimatisation happens faster when you conserve energy. Avoid strenuous efforts at the start of your hike and rest whenever possible. For every 1,000 metres of elevation gain, we recommend taking a rest day.
Staying hydrated and well-nourished
To maintain peak physical condition, hydration and nutrition are paramount at altitude. Drink at least two litres of water daily to offset fluid loss caused by low humidity. Do not wait until you feel thirsty; drink regularly in small amounts to stay properly hydrated all day long.
When it comes to nutrition, ensure you eat enough, particularly carbohydrates and proteins. This provides sufficient energy and supports red blood cell production.
Monitoring your symptoms
AMS is common at altitude and particularly dreaded by hikers. While early signs usually subside quickly, they can worsen. Symptoms such as breathlessness even at rest, severe fatigue, vomiting, severe headaches or hallucinations must alert you immediately.
If AMS persists, you must descend immediately. The primary risk is developing pulmonary or cerebral oedema, which is a life-threatening emergency.
Understanding acclimatisation time
From the very first hours at altitude, your body starts adapting. Proper acclimatisation nevertheless takes several days to several weeks, depending on the individual, duration and target altitude.
If you climb below 3,000 metres, you should acclimatise in just a few days. Between 4,000 and 5,000 metres, two weeks are typically required. Finally, a hike above 5,000 metres demands several weeks of acclimatisation.
Gear for high-altitude hiking
Technical clothing
For layering at altitude, the three-layer system is ideal. For your base layer, choose thermal underwear in merino wool or synthetic fabrics. They keep you warm while wicking away moisture.
For your mid-layer, choose fleece jackets or hiking down jackets. They are perfect for trapping heat in cold conditions. Finally, select hardshell jackets as your outer layer. They deliver optimal protection against rain, wind and snow. For trousers, opt for a water-repellent design.
High-grip footwear
Your trekking boots must be selected with care. At altitude, trails are often rougher, making solid ankle support crucial. Opt for a high-cut model. Also choose a rigid, high-traction sole for superior grip.
Depending on the season, prioritise waterproofing, breathability and adequate insulation. If you encounter snow at altitude, crampon-compatible boots are also recommended.
Accessories
Several accessories are essential for proper protection. Against UV rays, pack category 3 or 4 sunglasses, high-protection sunscreen (SPF 50+), and a cap or hat. To fight the cold, bring gloves, a beanie or headband, a neck gaiter and technical socks.
Hiking poles are recommended for improved stability. They also relieve strain on your joints during ascents and descents. Finally, your backpack must be suited to hiking, featuring a comfortable carrying system.
Safety gear
A hiking first-aid kit is essential at altitude. You can supplement it with an emergency whistle, a survival blanket and a headlamp with spare batteries.
For navigation gear, carry a topographic map with a compass, a GPS device and an altimeter. This allows you to track elevation gain and manage acclimatisation effectively. A mobile phone with an external battery pack or a VHF radio are vital for calling emergency services.
Practical extras
Other practical accessories round out your gear. You can pack a pair of binoculars, a field guide and a camera. They allow you to observe wildlife and flora and bring back precious memories.
You now know everything you need to know about high-altitude hiking. For a successful trip, remember to plan your route carefully and check mountain weather forecasts. This ensures you set off in the best possible conditions.
