Come into an elevated high plank position, with your hands placed against a chair seat (or equivalent raised surface), with your arms fully extended and your legs extended directly behind you, resting on the balls of your feet. This is your start position. Keeping you core braced, lower your chest towards the your hands by bending your elbows until your chest is just above your hands. Inhale as you do so. You should maintain an unbroken line from your head to yours toes throughout this lowering phase. Pause at the bottom of the movement, then press upwards from your chest and shoulders, straightening your arms as you return to the high plank position. Exhale as you do so. Repeat for the required number of reps (or time).