STARTING POSITION:
Select the appropriate weight of the medicine ball. Lie on a fitball facing down, it should be under your stomach. Your feet should be touching the floor and a wall behind you. Take the medicine ball in your hands and place it just above your head with your arms straight. Retract your shoulder blades.
MOVEMENT:
Keeping your lower back flat, start leaning forward slowly from the hips going down as much as possible while inhaling. Keep moving until you feel a good stretch in your hamstrings and then stop. Return to the starting position while you exhale. The medicine ball should be always in the same position.
TIPS: The exercise key is quality over quantity. The trick is to perform the exercise using proper form.