1. Come to a straight arm front plank position.
2. Keep your arms straight and push your body away from the floor slightly. It should feel as if your shoulder blades move further apart.
3. Keep your arms straight and bring your body closer to the floor. You will feel your shoulder blades coming closer together and closer to the spine.
4. Make sure to keep your shoulders low throughout this movement. It should feel as if the shoulder blades are low down and you are using the lower back muscles. Avoid tension in the upper traps.