running up stairs is great for your calf muscles you will really feel the pull on them as you go and then later on your quadriceps (thighs) will feel it as well it does greatly benefit your sprinting and endurance as well that is why it is so popular with boxers. another good one is to dribble a ball up the stairs bouncing it on every stair as you go as fast as you can greatly improves your ball handling but it isn't easy to do at a reasonable speed.