The best strengthen as a running back is the arms. This is in football.
running back & wide receiver
Barry Sanders
Gale Sayers or Walter Payton.
Adrian Peterson is the best.
The best running back is Tyler Olsen (aka ~T-23~) plays for the south sevier rams!
De' Anthony Thomas
Cardiovascular exercise is the best you can get to prepare yourself for a sport like football. Stretching your muscles is also good because it can help you prevent many kinds of injury, which a running back can sustain.
Priest Holmes, Landnien Tomlison, Darren Mcfadden
Tie between Javon Ringer and Jehu Caulcrick
In History Jim Brown.In the NFL right now Adrian Peterson, Arian Foster, or Chris Johnson all are really good.
The best is pele.