Secure a band to a fixed point. Set yourself up, with the band on one side of you, in a half kneeling position, tall spine.
Grip the band and remove any slack. Hips should remain facing forward, while the shoulders & torso are rotated towards the band, arms straight.
Engage your core and exhale as you rotate away from the band, so that your arms a pointed directly in front of you, shoulders are in line with your hips.
Squeeze at the top, core braced. Then slowly rotate your torso and arms back towards the band. Repeat for repetitions.
Keep a tall, neutral posture, arms should stay straight, and hips staying square.