Take position with a suitable weight dumbbell in one hand. Your feet are firmly planted at shoulder width, your head is up and your core is tight. The arm holding the dumbbell hangs down on your side, palm facing inward. On the opposing side, put your hand either behind your head or across your body. This is the starting position.
Commence the movement by bending the body from the waist whilst keeping the lower body stationary. Your working movement is toward the side not holding the dumbbell. Bend as far as you can to that side and hold for a second at the maximum range point.
When you have gone as far as you can, reverse the movement back past the starting position to the other side but without going to the end of your range.
Alternate the side holding the dumbbell upon completion of the set.