The limits for running are constantly being pushed further, with challenges increasing in duration, length, and risk. Marathon have extended to ultramarathons, which are opening up areas of mountain running at altitudes where breathing in is like sucking through a straw. Killian Jornet, a Spanish ultrarunning and ski mountaineer champion and has pushed his competitors even further, with blisteringly fast mountain ascents and descents. What was once technical climbing using ropes and harnesses is now the new trail for runners. Killian is setting records racing up such peaks as the Matterhorn and Kilimanjaro. And he seems to be having fun doing it.