You can do this chest exercise on the stability ball or on a more stable surface such as a stool.
Sit upright on the ball with perfect posture. Have the exercise band around your back and under both armpits. Holding the band in each hand, keep your elbows both at 90 degrees.
Keeping your upper arms parallel with the floor, bring your elbow closer together, squeezing the chest muscles. Make sure that your shoulders do not lift up towards your ears.
Keep going until your elbow are touching, then open your arms wide, returning to the start position. Repeat each side 10 to 12 times, then rest. Repeat the entire exercise sequence once or twice.