'Every day I run could be my last'

    By Gary Morley and Lisa Cohen, CNN
    Kayla Montgomery is a runner unlike any other. Every time she competes in a race, she knows she'll collapse in a sobbing heap at the finish line. It's become a fact of life since the teen was diagnosed with multiple sclerosis five years ago.

    About the series

    Human to Hero

    Twice a month, Human to Hero gets to the heart of what it takes to be a sporting star, exploring the discipline, dedication and determination involved, as well as the sources of inspiration for the world's best athletes.

    Watch on Wednesday May 20 at 1130, 1245, 1445, 2130, 2245, 2345 and Thursday May 21 at 0445 (All times GMT). Read about CNN's special reports policy

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  • Earl Bamber of New Zealand in action during the A1 GP qualifying round held at the Kyalami race track on February 21, 2009 in Gauteng, South Africa. (Photo by Duif du Toit/Gallo Images/Getty Images

    Up next ... Earl Bamber

    The New Zealand racing driver is moving his way up the motorsport ranks, and is preparing to drive in the prestigious Le Mans 24-hour endurance event in June. The 24-year-old won the 2014 Porsche Supercup, a series which runs during the race weekends of selected Formula One grands prix.