In high school I only ran track during the off season and pretty much half assed it, because all cared about was football. Looking back if you want to be better all around I would have played baseball and every thing i could get my hands on during the offseason just to stay in better shape and learn diffrent skills.
This would be better than running on a treadmill. If you are in season you should be busting ass and giving it your all so you don't want or need to run on a treadmill. It is what you put into it.