>> shepard: they came back from iraq and afghanistan missing arms and legs, facing serious challenges just to get their every day lives back. but now, as they take part in 100 k bike ride through a texas canyon, some veterans are inspiring people around them, including the former leader of the freerld. free world. >> that's what i'm talking about. >> shepard: he was once their boss, the man who sent them to war. >> these men and women were severely wounded and now they are riding mountain bikes in the canyon. >> former president george w. bush is right there alongside them on a three day, 62-mile trek through the texas desert. >> great opportunity that i thought i would never have in my life. to be able to come to some place that's this beautiful and ride with other wounded warriors and the president is just a very special thing for me. >> fox news medical contributor dr. marc siegel is there, too. >> you know, this ride is symbolic for reentering society. you are going uphills and down hills and going up mountains.