Starting Strength, 3rd Edition - Mark Rippetoe [35]
To maintain the vertical back angle required by the bar position, you must close the knee angle and open the hip angle; the front squat therefore involves inherently shorter hamstrings in the bottom position. A primary difference between the front squat and the squat is that the knees drive forward in the front squat. And if the knee angle gets too closed, some of the knee problems inherent in the front squat – the impingement of the posterior aspect of the meniscal cartilages between the acutely squeezed femoral and tibial condyles – start to show up where they shouldn’t. The cause of this knee-position error is often an incorrect understanding of where the back should be in the squat.
If your concept of the low-bar back squat involves a mental image of your doing the movement with your back in a vertical position, your perception of what you’re supposed to be doing is wrong, and it will cause your knees to be too far forward. If your torso is too vertical, your knees will be forced forward to maintain the bar/mid-foot balance position. The layman’s advice to “lift with your legs, not your back” might be part of the problem because most people interpret this advice as involving a vertical torso and the legs pushing the floor.
Figure 2-47. Quite often, the mental image of the squat involves a vertical torso like a front squat, a position that kills posterior chain involvement. The correct back angle is horizontal enough that efficient hip-drive mechanics are used, and this back angle awareness involves the correct mental image of where your torso actually is during the squat. Don’t be afraid to lean over, sit back, and shove your knees out.
The saying should be “lift with your hips, not your back,” because “lifting with your back” is what happens when you bend over to pick something up and round your spine into flexion. Leaning over is a normal part of the squat; it is required if the bar is to remain in balance over your mid-foot. The correct mental picture, discussed below, usually fixes this problem.
If it doesn’t, there are other things that can get the knees back. If the weight is on the heels during the squat, the knees can’t be too far forward. Think about your heels, and how it feels to have your weight balanced on them. Assume your squat stance, pick up your toes, and rock back onto your heels. Once your weight is on your heels, shove your knees out and squat. When you squat from the heels, your knees stay back, and if you stay in balance, your back angle will have adjusted to a more horizontal position as well. Now, you will not be able to continue to squat on your heels because this is also an unbalanced position. But after three or four reps, this trick will have done its job and you will have settled into the middle of your feet with your knees in the correct position, not too far out over the toes. This position will feel balanced and strong, and done correctly a few times, it will be the one you favor from then on.
A different problem, often encountered in more advanced trainees, is the tendency to let the knees slide forward as the bottom approaches. This problem usually develops over time, and the embedded movement pattern can be hard to fix if you let it go uncorrected too long. And it is potentially complicated. If your knees move forward at the bottom of the squat, you may have relaxed your quads, which hold the knees open; the closed knee angle in turn shortens the hamstrings, which then are slacked distally and therefore cannot be used effectively for proximal hip extension. Quads maintain the knee angle, which in turn anchors the hamstrings as they tighten with greater squat depth and a more closed hip angle so that they can extend the hips on the way up. Or you may have relaxed the hamstrings’ tension on the tibias, dorsiflexed your ankles, and shifted forward to your toes from the bottom. The soleus anchors