Since the squat is a whole-body exercise, when you get stronger with the movement you generally get stronger with the entire body, including the trunk muscles. In fact, many Olympic weightlifters get stronger with their lifts without doing direct abdominal exercises. If your squat gets stronger, your trunk naturally gets stronger, simply by way of its direct involvement with every single rep.
The reason you feel it in your trunk (or “core”) while squatting in the 400s is because your best squat is 375 lbs. That’s a big jump. And the reason you didn’t feel the 400 pounds in your legs was probably because you didn’t squat low enough. In the mechanical link of the squat, your back simply felt it before your legs.
Those who squat with a caved-in back simply need to correct their technique, and sometimes this correction requires a temporary decrease in weight until positive adaptation occurs in every segment of the kinetic chain for this exercise.
Increased lumbar lordosis, as a static configuration (posture), does not mean stretched and weakened muscle fibers in the abs; Janda has no scientific support for his claim of sort. In a case such as increased lumbar lordosis, a lengthening adaptation has most likely occured, resulting in the addition of sarcomere numbers. This means cross-bridging opportunity is returned to normal. This could explain the more recent research that shows a lack of relationship between posture and strength.
Although Olympic weightlifters don’t often train abs directly, the lifters at Westside Barbell utilizes a lot of assistant exercises – including lower back and some abs. They even utilize the abdominal push-outs against a weight belt while doing squats (as someone has mentioned in this thread).
Bottom line is this: if your squat is not going up, it could possibly be the design of the squat program, not the individual body parts. Try box squats, speed squats, dead-squats, max squats, breathing squats, jump squats, chain squats, band squats – utilizing a sensible variety of percentages. The magic lies in the periodized squat program, not a certain exercise for an isolated body part.
And, will someone please explain to me how Pilates can get the torso to generate the kind of force output required by a 400-pound squat?
Thanks,
John