One of the most storied and feared stretches in running is in the Boston Marathon – Heartbreak Hill is 32 kilometres after the start. The 27-metre elevation gain over half a kilometre would be a painful climb in any marathon, but here it's compounded because it occurs at the distance where many runners hit the proverbial wall.

Last April, Erik Rasmussen, a 42-year old trail seeker, runner and triathlete, finished the Boston marathon at 2:42:35, good for 241st overall. But in August, he became the first to complete what may arguably be the world's toughest 42.2km race: up the face of Kilimanjaro, the world's tallest free-standing mountain. In this debut run, he crossed five ecological zones, from bushlands through a rainforest and up to the glacier-capped summit at 5895 metres. It took him eight hours and 33 minutes.

Bloomberg