Scared witless and surrounded by a sea of people, Lizzy Hawker stands in the church square at the centre of Chamonix on a late August evening, waiting for the start of the Ultra Trail du Mont Blanc.

The mountains towering over the pack of runners promise a grueling 8,600 metres of ascent and descent over 158 kilometres of challenging terrain that will test the feet, legs, heart and mind.

These nervous moments before the race signal not just the beginning of nearly twenty-seven hours of effort that saw Lizzy finish as first woman, but the start of the...