The Duo Ball is particularly effective for massaging and releasing tensions in parallel lines of muscles e.g. along the thoracic and lumbar spine - The areas where we feel upper and lower back pain. It can also be used to target the upper thighs tight hips calfs and the areas around the achilles tendon. A recent study has identified the Duo Ball as a highly effective tool in the workplace to reduce muscle stiffness and prevent pain symptoms related to prolonged periods of sitting.