“Assistance” Exercises – What do They Assist? | Mark Rippetoe

Here's a better question: if I do leg extensions for 6 weeks and go from 90 to 130, does that make my squat go up, or if I take my squat up 5 pounds per workout from 185 to 365 x 5, what happens to my leg extension? If you've had any experience with this, you know that leg extensions do not drive the squat up, and that squats do in fact drive up the leg extension. And this is true of any single-joint assistance exercise. They don't actually “assist” the primary barbell exercises – the barbell exercises “assist” the isolation exercises. So which ones are the Assistance Exercises?