Back Exercises: Back Release
Do this exercise on your hands and knees. Keep your knees under your hips and your hands under your shoulders. Keep your spine in a neutral position (not arched or sagging). Be sure to maintain your neck’s natural curve.
Relax your abdominal and buttocks muscles, lift your head, and let your back sag. Be sure to keep your weight evenly distributed. Don’t sit back on your hips. 
Hold for 5 seconds.
Return to starting position.
Repeat 5 times.