Team Hoyt is a father (Dick Hoyt) and son (Rick Hoyt, b. 1962) in Massachusetts who compete together in marathons, triathlons, and other athletic endeavors. Rick has cerebral palsy, caused by loss of oxygen to his brain at birth because his umbilical cord was wrapped around his neck. Dick pulls him in a special boat as they swim, carries him in a special seat up front as they bike, and pushes him in a special wheelchair as they run.

More background can be found in this interview:
http://www.youtube.com/watch?v=dDnrLv6z-mM

Oh, and please excuse the religious connotation in the video.