Toned arms? Check. Killer abs? Check. Power pins, check, check check. If you want a supermodel body, Christina Howells and Charli Cohen AKA That Girl London are the ladies to show you how to achieve it. They understand you're busy but still want a killer bod so they're workouts are time efficient while still maintaining maxium impact. Watch the video above for an exclusive resistance band workout. Plus visit That Girl London and enter the code INSTYLE20 to receive 20 per cent off all their online workouts. You and your perfect summer body can thank us later.