Main Set: Breaststroke Getting the right anatomical tools for doing fast breaststroke is very important. Internal rotation of the hip, pronation of the ankle and lumbar spine extension are the three important qualities needed for a strong breaststroke kick. Plus strength. Plus fitness. Some swimmers are born with the breaststroke kicking tools, and some are not. If you don’t have the necessary flexibility for breaststroke, it doesn’t mean you have to throw in the towel. You just need to know what to do to improve.