Core stability training - dumbbells to side

Lie on your back with a stability ball under your back.
Hold dumbbells in each hand with straight arms.
Tight your core muscles and maintain your back straight.
Raise dumbbells towards the ceiling.
When ready, drop both dumbbells to the side.
Try not to move other body parts while lowering your arms down.
Slowly return to the starting position and repeat on the opposite side.