Active prone back extensions (Trunk extension/scapular retraction strengthening, arms in W position, prone; 01)

Lie on your front with your hands by your shoulders and your elbows by your side.
Squeeze your shoulder blades together so your elbows are close to your side, and your hands are off the floor.
Arch your back so your torso comes off the floor.
Maintain your shoulder blades in a squeezed position throughout the duration of the exercise while keeping the buttock muscles tight.
Your lower body remains in contact with the floor.