Your backstroke can only be fast if you are using both hands and your feet to the best of your ability. Don’t get caught only moving one arm at a time. Instead, be sure to continue to rotate both arms at the same time like a windmill. When one arm is up; the other should be down. This way you never stop moving forward. While doing this, make sure to keep your kick moving as fast as you can; your legs are your friend! Fast turns and streamlines can make all the difference in backstroke.