At altitude, the air contains less oxygen per breath, so your body has to work harder to deliver the same amount of oxygen to your muscles. Even at moderate elevations — roughly 1,500 to 2,500 metres — most people notice faster breathing, a higher heart rate, and a feeling of heaviness during exercise that would feel easy at sea level. This is normal physiology, not a lack of fitness.

High altitude training has attracted attention because athletes who spend time at altitude often return to sea level with improved endurance. The body adapts by producing more red blood cells, which carry oxygen more efficiently. But those adaptations take time — typically two to four weeks — and they come with trade-offs, including reduced training intensity and possible sleep disruption.

The golden rule is to acclimatise gradually. If you can, spend a day or two at moderate elevation doing only light activity before attempting anything strenuous. On your first outing, cut your usual effort roughly in half: walk instead of running, take frequent breaks, and judge effort by feel rather than pace or distance. Drink more water than usual, because altitude increases fluid loss.

Watch for altitude sickness, which can affect anyone regardless of fitness. Headache, nausea, dizziness, unusual fatigue, and poor sleep are early warning signs. Mild symptoms often improve with rest, fluids, and a day without further ascent, but if symptoms worsen — especially confusion, difficulty walking straight, or breathlessness at rest — descend promptly and seek medical help.

Once you are acclimatised, build gradually. Short, frequent outings beat one huge day, and walking steep terrain is excellent training in itself. Strength work for legs and core helps with climbs and descents. Most beginners find that after a few days, breathing feels easier and effort drops noticeably. Enjoy the process rather than chasing numbers.

A gentle acclimatisation schedule makes the first days far more comfortable. As a rough guide, spend your first day at altitude on easy walking and light activity only, keep the second day moderate, and save anything strenuous for day three or later. A classic mountaineering rule is to sleep no more than about three hundred to five hundred metres higher than the previous night once you are above roughly three thousand metres, though at moderate elevations the rule matters less. Clothing matters more than beginners expect: dress in layers you can add or remove quickly, protect your head and hands from wind, and carry a waterproof layer even when the morning looks clear, since mountain weather changes fast. Sun protection is essential, as ultraviolet intensity rises with elevation and snow or light rock reflects it back. Eat regularly even if your appetite is low, favouring familiar, easily digested foods, and keep drinking steadily rather than waiting for thirst. If a member of your group develops worsening symptoms, descend together and seek help early; altitude illness rewards prompt action and punishes delay.