ERECTOR SPINAE

These are very small muscles that run up both sides of your spine from your hip to your neck  They branch off to attach at the ribs and spine.   These muscles tend to be very tight and weak outside of their normal range.   Their main job is to keep you upright.  They also help with twisting and bending of your trunk.

 Most gyms will have a back extension bench that will work the erector spinae.

At home you can perform the Cobra:  Lie facedown with legs extended, toes pointed, hands flat and palms down, elbows bent and wrists in line with shoulders.  Rest forehead on the floor and pull your belly in.  Roll your shoulders back engaging your back muscles.  Inhale and press palms against the floor and lift your upper body arching your back.  Hold for 5 seconds and slowly return to start position.  Do 10 to 15 reps.  Photo below.