STARTING POSITION:
Take two bottles of water. Stand up straight with the bottles in your hands. You should use a neutral grip. Lift the bottles just above of you extending your arms. Contract your pelvic floor and core while keeping your chest up.
MOVEMENT:
Slowly lower the bottles just behind you by bending your arms while you inhale. Return to the starting position in a strong movement while you exhale.
TIPS: While your are doing the exercise, move only the elbow joint, make sure you don't move any other part of your body.