Running at altitude

Above about 1,500 m, each breath brings less oxygen: the same pace costs more, so slow down and run by effort or heart rate.

• Expect a higher heart rate and a slower pace: between 1,500 and 2,500 m, often 3 to 8 % slower at the same effort, more higher up.
• Acclimatisation takes time: the first adjustments come in 3 to 5 days, a fuller adaptation in 2 to 3 weeks.
• For the first days, keep runs easy and shorter, drink more as the air is dry, protect yourself from the sun and sleep well.
• Headache, nausea, poor sleep or unusual breathlessness are signs of altitude sickness: rest, and go down if they worsen. Breathlessness at rest or confusion needs urgent medical help.