Resisted trunk rotation on a stability ball (Neutral spine stabilization, on stability ball, with upper trunk rotation, with band (to side))

Sit on a stability ball with both feet firmly on the floor.
Attach a resistance band to something secure, around waist height.
Hold the end of the resistance band with both hands.
Find your neutral sitting posture and hold this position.
Hold the band out in front of you, and rotate your body away from the band, keeping your elbows straight.
Hold this position, then control the movement as you return to the neutral position.