Lie on your side on a stability ball. The ball should be under your lower waist and hip.
Allow your upper body to bend over the surface of the ball.
Extend your legs and position one in front of the other for stability.
Place your hands behind your neck or head.
Exhale as you laterally flex your waist and raise your upper body off the ball until you feel a mild stretch in your side.
Hold for a count of two.
Inhale as you slowly lower your upper body to the starting position.
Repeat for the prescribed number of repetitions.
Repeat the exercise on your opposite side.
Comments and tips
Keep your neck neutral.
Keep the movement slow.
The stability ball side bend is effective at targeting the obliques, strengthening the lateral flexion of your spine, improving spinal mobility, and helping to develop a strong and stable core.
Many people make the mistake of keeping most of the movement in their lower (lumbar) spine. Therefore, make sure that there is movement throughout your lumbar spine (which is built for stability) and your thoracic (upper) spine (which is built for mobility).
To improve your stability, position your feet against a wall. See video.
Make the stability ball side bend easier by positioning your hip lower on the ball.
Make it more difficult by holding a weight plate behind your head.