That’s a tough one to get in to one name! :). Hmmm… Your athletes will benefit from a core class in so many ways. You could always keep the name simple, and then have a small description of your class to further elaborate the benefits and goals. I include hips as part of the core (includes various muscles from the diaphragm to the pelvic floor), but here are a few ideas, keeping in mind you work with athletes:
Core Performance for the Athlete
Core Conditioning for the Athlete
Strong Core and More: Knee Injury Prevention Program
Off the Floor Core: Keeping Knees Strong
Hope some of these combinations inspire you to come up with a name. Good luck!