Start in a tabletop position, kneeling on the floor with your hands under your shoulders. Reach your opposite arm and leg away from the centre of your body until they are straight. When bringing them back towards the body have the elbow and knee meet underneath you – this will involve rounding your back slightly. For maximum results, work one side for a number of reps before switching sides. Keep your core tight during the exercise to avoid straining your low back during the extension.