Its common for a coach to tell you to "brace your core" or "squeeze your abs" when squatting, its fair to say after todays midline madness, you're going to know where that is tomorrow. Its a good pain though, don't pretend its not......
Without reducing the weight throughout, establish a 1RM in the following:
- Overhead Squat
- Front Squat
- Back Squat
Start light and Keep adding weight until you fail each movement. for example, when you fail the OHS, use that weight as the starting weight for your Front Squat and so on with smaller increments.