Ihave been thinking a lot about something that I believe doesn't get nearly enough airtime in outdoor adventure circles: the nitty gritty behind physical performance at high altitude. Which really covers everything from trekking to Machu Picchu and up Kilimanjaro to climbing on Aconcagua to learning how to swing ice tools on Mount Baker! After years of guiding and personal high-altitude pursuits, I'll say this much: there are 3 things I wish every climber and trekker knew before stepping above 14,000 ft.