Set-up: Lie face down on the ground with your arms straight and perpendicular to your torso with palms facing down.
Movement: Bracing through your core, and focusing on your upper back, slowly raise one arm off the ground. Pause momentarily then return that arm to the start position and alternate with the other side.
Emphasis: Do not swing. Do not raise your torso too far off the ground and avoid hyperextending in the low back. Brace through your core throughout the movement.