Chile's Atacama desert is Andy's last stop before the Antarctic, a tougher place to run would be hard to find.
It is the driest hot desert on earth, and it is also at altitude so there is limited oxygen in the air - perhaps not the ideal location for a marathon, yet, dozens of runners travel to compete at 14,100ft in the Volcano Marathon.
Andy says: "It is one of the interesting perversities of human nature that for many of us in the developed world, as our day-to-day lives become easier, a significant number of us still feel the need to find new and interesting ways to push ourselves physically and mentally to the limit, be it with a trip to the Antarctic ice, or here where this committed bunch are getting ready to run a marathon where they share a start line with one of the most active volcanoes in South America."
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Source: Al Jazeera