Athletes do a lot of different things to keep in shape. The really good ones like to push themselves. They challenge themselves to be better every day. I include Jamaal Charles in this category. Charles has challenged himself to become a better athlete. Running track in the offseason speaks to his character as an athlete. It's a great trait to have.
However, I wonder whether or not it's a good thing for him as a football player. The conditioning required for track and football are very different. Track focuses more on speed and cardio whereas football (for a RB) is geared more towards strength and agility more than raw speed.
Now, I don't doubt that Charles can get back into football shape before the start of the season. We all know that Todd Haley will see to that personally. I simply believe that he's making it harder on himself. Especially considering that there are injury concerns with him. Charles had to come out of the game several times last season because he was dinged up. That's a big sign that a RB needs to be hitting the weight room. I'm not concerned about him getting injured while running track. He has the money to hire a quality coach and trainer, and we know his agent won't let him get to out of hand.
Maybe I'm putting too much into it, but I'd rather see him in the gym with Thomas Jones working on getting some more muscle mass, rather than getting too focused on his running. There is a reason why we don't see very many two-sport athletes at the professional level.