To the outside world, Markelle Taylor was an inmate. But behind the walls at San Quentin State Prison, he had a different reputation — the fastest athlete with unmatched grit. Now, he's racing on the world's biggest stages as a free man and making strides toward a better life. As part of the "CBS Mornings" series "Pushing the Limits," our lead national correspondent David Begnaud joined Taylor as he trains for his next race and overcomes obstacles along the way.