It was Monday night, August 3, at the 1992 Olympics in Barcelona, Spain. At the track and field stadium, the gun sounded for the 400-meter semifinals. About 100 meters into the race, Britain’s Derek Redmond crumpled to the track with a torn right hamstring. Medical attendants rushed out to assist him, but as they approached Redmond, he waved them all aside, struggled to his feet, and crawled and hopped in a desperate effort to finish the race. Four years earlier he had also qualified