his strengthens the core muscles involved in “anti-extension” – ie, any movement that resists extending the lower back – which applies to anyone who works at a desk. It uses all your abdominal muscles, but also works the legs, glutes (your bum) and shoulders. The key is to keep your hips in line with the rest of your body. Don’t let them fall towards the floor or stick up towards the ceiling: easier said than done. a) Starting from a kneeling position, come into a forearm plank position; bend your elbows so they are parallel with the floor, and turn your palms flat against it. b) Activate your thighs to straighten your legs. c) Push your elbows and palms into the floor, so your shoulder blades open up. d) Tuck your tailbone under, squeeze your glutes and draw your belly inward. e) Imagine that you are pulling your feet towards your elbows and your elbows towards your feet. Hold for 30-60 seconds (or longer if possible). f) Repeat three times.