And he determined this so-called imbalance how?? By “core” muscles are you referring to the musculature on the anterior side of the torso? I only ask this because “core” seems to mean different things to different people. Is this yet another “isolationist” solution to a problem that might be multi-factorial? Maybe the more observant coaches on our board can chime in regarding her form, but I’m not sure any could determine by observation alone that she has an imbalance between her “core” muscles and lower back. If anyone can please enlighten us!