As the 2012 Olympic Games approaches, Al Jazeera is taking a look at athletes from across the world who have overcome exceptional hurdles to become champions. Kayla Harrison, a US judo champion, overcame sexual abuse by a former coach. She now aims to become the first person from her country to win gold in her sport. In the latest in our 'Against all odds' series, Al Jazeera's Andy Gallacher reports from Miami.