Misconception #1. Freestyle “catch-up stroke” is a viable technique.
Research shows that catch-up stroke is biomechanically ineffective, physiologically inefficient, anatomically stressful, and counterproductive from a skill-learning perspective. Biomechanically, catch-up stroke produces an ineffective arm synchronization, where no force is generated by either arm on two phases of each stroke cycle. Physiologically, there is an inefficient use of energy as the body velocity fluctuates. (The energy cost of speeding up on every stroke is greater than maintaining a relatively constant velocity.) Anatomically, when the arm is held in position in front of the body and parallel to the surface, the angle at the shoulder reduces the space for the soft tissue between the upper arm and shoulder. This position causes irritation and decreased blood flow and is classically related to shoulder impingement. (Torso rotation with this arm position further stresses the shoulder.) And from a skill-learning perspective, research shows that swimmers don’t use catch-up stroke when swimming fast, so why reinforce a technique that you’re not going to use for racing?