Sorry I know it wasn't directed at me, but core contractions is not something anybody would ever ever have to think about. It happens in all athletic movements running, jumping, swinging, throwing etc, all sports, hockey, tennis, soccer etc. TTB is something you would definitely need to think about, it's unique, it's forced, it's not natural at all. JMHOI seriously doubt they have any thought of core contractions either, but that doesn't mean they don't happen.