High-altitude basics

Climb high, sleep low where you can, and don't jump your sleeping altitude too far in a day. The well-graded routes here do this deliberately: short distances on the high days, a night lower early on to let the body adjust. Rushing the gain is the single biggest risk factor, and it's entirely within your control.

Know the early signs of acute mountain sickness — headache, nausea, dizziness, poor sleep, breathlessness at rest. Mild symptoms mean stop going up; rest at that altitude until they pass. Symptoms that worsen mean go down, and going down even a few hundred metres usually helps fast. Never push higher to 'get it over with'. On the GHBT, ask for backup from the team — the guide carries oxygen and the support vehicle is never far — but the judgement to stop or descend is the rider's to respect.

Cold compounds everything up high, even in summer. Above the passes the temperature drops sharply once the sun is off the road, and weather turns quickly. Carry a windproof shell and a warm layer within reach, protect your hands and head, and don't let a long descent chill you to the point of bad decisions. Sun is the flip side — at altitude it burns hard, so cover up and use good sun protection.