Secure a long resistance band round a pull up bar. Standing under a pull up bar, reach up and hold onto the bar with an underhand grip whilst also stepping your feet into the end of the resistance band. Make sure your hands are shoulder width apart and elbows are close to your body. Keep your arms straight and hang from the bar. Keeping your body straight and not swinging your weight, pull your body up towards the bar by pulling your elbows down towards your torso, exhaling as you do so. Continue lifting your body up until your chest is nearly touching the bar. Pause at the top of the movement and squeeze your lats and middle back. Once your lats have completely contracted at the top of the movement, slowly lower your body to the start position, inhaling as you do so. As you progress in strength you can remove the resistance band.