This is Misty Hyman demonstrating the kick she developed in the late 90’s. She went on to win gold in the 200m butterfly in Sydney in 2000.
And here is a video of how she used to do it before there were rules about how far you could kick…
Here is the kick broken down:
Full extension, arms straight and in line with back. Legs are limber (relatively straight) and her hips are pressing them BACK. Keeping the arms aligned with the back is the most difficult position to manage for most people. It takes great shoulder flexibility. The rest of the motion is possible for almost anyone.
Her shoulders shrug UP AND STAY HIGH to start her upper body PRESS. You can see her arms moving toward us with respect to the black segment of the lane line.
Shoulders continue to work in a SHRUGGED position. Her UPPER BACK is rounding and the UPPER ABS and SHOULDERS/BACK are making the movement happen, NOT THE ARMS. Her abs contracting have pulled her hips forward but there is NO ACTIVE KICK as yet.
She continues to contract her abs, pulling her arms forward, as her ACTIVE KICK begins. This is the UNCOILING of all the abdominal tension built in the above two frames.
Her upper body is now stable and her legs explode in extension.
Her kick finishes and almost immediately her hands begin to lead her upper body back the other direction – but her arms remain straight.
Her straight arms realign with her upper back, and her legs begin to recover in a LOCK-KNEED position.
Hands lead her upper body as she pulls her straight legs back. Her core muscles are tight and stable, which allows her hips to pull her legs back.
Moving to the “superman” position. Her upper back and arms are CATCHING water and PULLING her forward.
Back to the starting position…
Note: she has traveled almost the same distance during the front and back kicks. But it’s the powerful, well-timed contraction along the front of her body, starting from the first movement of her shoulders to the last extension of her kick, that provides the bulk of the power.