This exercise targets the oblique muscles which control the ability to side bend and rotate the trunk. Strengthening these muscles can help protect your spine from injury.
Start in standing with your feet hip-width apart and your shoulders stacked over your hips. Your arms should be relaxed by your sides.
While maintaining a forward-facing position, slowly lean your trunk to the side, reaching one hand down your leg, then return to an upright position. Repeat on this side. Then repeat on the other side.