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
Hiking at altitude has a significant effect on the body. The higher you climb, the lower the atmospheric pressure. Less oxygen reaches the blood, and the body enters a state of hypoxia. You may then notice difficulty breathing and a drop in 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.
Avoid overexertion, too. You acclimatise faster when you conserve your energy. Avoid intense exertion at the start of your hike and rest whenever you can. We also recommend taking a rest day for every 1,000 metres of altitude gained.
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 to below 3,000 metres, you should acclimatise in just a few days. Between 4,000 and 5,000 metres, it generally takes two weeks. A hike at over 5,000 metres requires several weeks of acclimatisation.
Gear for high-altitude hiking
Technical clothing
For clothing at altitude, the three-layer system is ideal. For your base layer, choose thermal underwear made from merino wool or synthetic fabric. It keeps you warm while wicking away sweat.
For your mid-layer, choose a fleece jacket or hiking down jacket. Both are well suited to retaining heat in cold weather. For your outer layer, choose a hardshell jacket. It provides protection from rain, wind and snow. For trousers, opt for a water-repellent pair.
High-grip footwear
Choose your trekking boots carefully. Trails at altitude are often steeper, so good ankle support is essential. Opt for a high-cut boot and choose a stiff sole with good grip for better traction.
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 better stability. They also take pressure off your joints on climbs and descents. Finally, your backpack should be suited to the hike, with a comfortable carrying system.
Safety gear
A hiking first aid kit is essential at altitude. You can add an emergency whistle, a survival blanket and a head torch 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.
