Originally Posted by
Mark Rippetoe
If you are performing a movement that is only possible with the use of a muscle group moving a skeletal component through a defined ROM, then in the absence of neurological damage, you are using that muscle. For example, "gluteal amnesia" is quite popular right now. I just got another post about it. It is supposed to impair your ability to squat until you do special exercises that somehow remind your glutes what they are anatomically positioned to be doing anyway. The reality is that the nervous system manages the many dozens of muscles involved in the squat through a pattern of neurological action called a motor pathway. No single component of the pathway need be micromanaged by your conscious activity, because you can't separate the single component from all the other activity -- there are too many muscles doing their jobs all at the same time. This is why we chose the exercise in the first place: we want lots of muscles working together under a load, because that is how the body works, and this is how it should be trained. The way you ensure that all the muscles are working correctly is to use perfect technique, i.e. move the skeletal components in a way that most efficiently accomplishes the task. We spend quite a bit of time in the book explaining what that means and why. Muscles move bones, so if you are moving your skeletal components in the correct way, the muscles that move them correctly -- in the absence of nerve damage -- are moving them, because bones don't move by themselves. The muscles are thus "working" or "firing" or "activating", whatever your PT wants to call it this week. So, when you squat, your hips extend because that's how you get back up. The glutes, originating on the ilium and inserting on the greater trochanter, extend the hips and externally rotate the femurs when they contract, because when you pull their origin and insertion closer together, that's what happens. If you keep your femurs in external rotation (abduction) at the bottom, and you stand back up, your glutes have "fired", because firing the glutes is how you extended your hips with your knees out. IF, THEN. Very simple, really. In the absence of neurological damage, hamstrings work the same way. Read about it in the excellent book you have just purchased.