Joe, I use a Swiss Ball with a training/Medecine and whilst I can't say that it's definitely beneficial, what I can say is that it definitely adds variety to a weekly training schedule. If you're a dediciated, coimmitted runner it may not be of any benefit, but as a multi-sported person, it's good fun. I also have a copy of 'Strength Ball Training' which is a very good book, with nice photos showing 69 exercises for all round body workouts.