As you can see, there isn’t much to this exercise. It is a standard plank, but we’ve just changed the surface up a bit. Rather than being on solid ground, I’ve put my forearms on the physioball here. The instability of the physioball is going to make me use my core even more in order to stay still and in control. At the end I’ve added a roll-out to the plank. This simple add-on to the exercise is going to fire the core up even more. The further you go out, the harder your core is going to have to work to stay stationary. Focus the entire time on a tight, flat core.