Running the ball can be the most exciting aspect of the game to watch. It is also one of the toughest. When moving the ball on the ground, every yard must be fought for.
Agility and quickness are needed to advance the ball. Blockers can
create gaps up, finding the holes in the defense, but only for a few
seconds at a time. Body control is essential. Tremendous physical
strength is also needed to power through tackles.
Due to the demanding nature of the position, teams frequently carry multiple running backs. Usually a fullback or power running back is used in short yardage situations when the defense will be guarding against the run and the only yards gained will be the ones muscled out. The team's main running back is usually faster and can double as a receiver.
What sets a good back a part is being able to move in all directions on the field. Moving east to west is just as important as moving north and south.
Running backs are among the least durable players in the game. In the NFL, top running backs are viable for around 5 years before their careers are chipped away by injuries.