If you're using dumbbells, you haven't got to fiddle with weight plates, you'll never need to stress about barbell collars and you can guarantee that there will always be a pair of dumbbells available on the gym floor. Something we can't guarantee about the weight bench – especially if it's chest day. But more fool them. For those in the know, there's a pot of gold waiting for you, a world of exercises you never knew existed, and workouts that will achieve the same results as those lifting heavy iron from the floor. And we're going to show you how