Hamstrings and the Squat

[Scott Beall]

In the past, I believed (and I think you previously taught at the seminars) that the hamstrings were the primary muscle involved that mad the Low-Bar Squat much stronger than the Front Squat or High-Bar Squat. Is this still your understanding?

I ask because we know that the hamstrings do not shorten nor lengthen significantly in the Squat. However, I we also know that in the HBS or Front Squat, there is much less tension of the hamstrings and therefore the hamstrings contribute little to performing these two lifts.

So my second questions is, if the hamstrings are the primary muscle that make the LBS damn stronger than the other two versions of the Squat, is it because of the stability and security they provide to the hips and knees, and ultimately, the entire barbell-lifter system?

I can also imagine that since the Low-Bar Squat has a smaller hip angle, the gluteals would be lengthened further, thus allowing for more power generation from them. I imagine (and feel when performing a body squat) the same if true for the adductors.

Thank you for your input.

[Mark Rippetoe]

1. As best we know, this is true. The added muscle mass of the hamstrings enables more weight to be lifted.

2. The hamstrings enable a more horizontal back angle to be used, thus enabling the hip extensors to more effectively add their force production to that of the knee extensors.

[Scott Beall]

And are the hip extensors able to generate more force production because they are stretched (lengthened) more than with a more vertical back angle?

Also, if the hamstrings probably do not lengthen significantly on the eccentric nor shorten on the concentric of the Squat, and essentially function isometrically, why do we refer to them as extensors? Do we still refer to a muscle as an extensor even if it doesn't do the extending itself, but simply helps the other prime movers do their job?

[Mark Rippetoe]

1. Yes, and they are forced to generate more force because they are supporting a longer moment arm.

2. Anatomists call them "extensors" because they are in a position to extend the hips.

These are good questions for Saturday morning at the seminar. You should attend again and ask better questions.