The Prop Up exercise is to improve spinal mobility. Lie on your stomach with your chest and head resting on your arms. If you feel comfortable in this position, you can proceed to prop up on your forearms, allowing your lower back to move into extension. Keep your hip bones on the floor. This should not be a painful position, but you may feel like it stretches you. Hold the position for 5 seconds, and if directed by your coach - longer. You should never feel pain with this.