Desert RunnersExecutive producer Dean Karnazes set a precedent in 2009 by being the first person to complete the Four Desert Ultramarathon Series, running a total of 1000km in the space of a year. Now, every year a diverse and disparate group of motivated daredevils converge on four of the most challenging racecourses on Earth — Chile’s Atacama desert, China’s Gobi desert, Egypt’s Sahara desert and, finally, Antarctica.

Jennifer Steinman’s film follows four participants in the 2010 event, tracking the attempts of British self-defence instructor Tremaine, American ex-baseball player Ricky, Australian law student Samantha and 56 year-old Irish businessman Dave to follow in Dean’s footprints. Each has their own individual reason for competing — Tremaine is running in honour of his late wife; Samantha wants to be the first woman to finish — and all four will face their own individual struggles as they tackle the four 250km races.

As impressive as the spectacle undoubtedly is — it’s difficult to imagine running a normal marathon in such extreme temperatures, let alone four extra-long ones — it takes the human element to provide audiences with a stake in the competition. Steinman — who has over fifteen years experience working in television and film — clearly knows this, and after a text-heavy introduction to the terms and conditions she lets the competitors carry the film — in addition to their food, equipment and emotional baggage.

The film, following each race in chronological order, is anything but repetitive, with the changing terrain and increasingly worn-down runners giving each course its own distinctive personality. Despite the physical strain, each of the competitors manages to remain relatively upbeat and optimistic throughout the Chilean leg of their ordeal, before the trauma begins to manifest itself over the consecutive races and a number of shocking and completely unpredictable developments start to infringe on the fun.

It really is an astonishing piece of work, as spectacular as it is emotionally exhausting, as dynamic as it is rooted in the moment. The individual journeys are by turns uplifting, entertaining and completely devastating, and when some of the competitors are forced to reconsider their place in the competition you can feel the sacrifice they are having to make.