Start seated on the edge of a chair (or equivalent) with a short band just above your knees. Your feet should be just wider than shoulder width. Come onto the balls of your feet and lean forward slightly, keeping a neutral spine. This is your start position. Drive your knees out forcefully against the band. Pause for a count of one, keeping the tension in your glutes and then bring your knees back to centre, inhaling as you do so. Repeat.