I'm just a hobby jogger but my son is a very competitive high school distance runner. Anyway I recently bought Greg McMillan's DVD on developing core strength and am trying to do the exercises along with my son. They are things like side bridges, slow sit ups, leg lifts etc.
My question is, how often do most runners do core work? Daily? Every other day? Different for competitive runners, in season vs summer? I like the exercises and can already feel them getting easier, just not sure how often I/my son should do them.