| Matlock | 07-15-2011 09:54 PM |
Currently reading Rippetoe's Starting Strength: Quote:
Squat depth - safety and Importance
The full squat is the preferred lower body exercise for safety as well as athletic strength.
The squat, when performed correctly, is not only the safest leg exercise for the knees, it produces a
more stable knee than any other leg exercise. The important part of the last statement is the
"when performed correctly" qualifier. Correctly is deep, with hips dropping below level with the
top of the patella. Correctly is full range of motion.
Any squat that is not deep is a partial squat, and partial squats stress the knee and the
quadriceps without stressing the glutes, the adductors, and the hamstrings. The hamstrings, groin muscles, and glutes perform their function in the squat when the hips are stretched to the point of
full flexion, where they get tight — the deep squat position (fig. 2-3). The hamstring muscles,
attached to the tibia and to the ischial tuberosity of the pelvis, and the adductors, attached
between the medial femur and various points on the medial pelvis, reach a fu]l stretch at the very
bottom of the squat, where the pelvis tilts forward with the torso, stretching the ends of the
muscles apart. At this stretched position they provide a slight rebound out of the bottom, which
will look ]ike a "bounce," and which you will l e a r n more about later. The tension of the stretch
pulls the tibia backwards, the posterior direction, balancing the forward-pulling force produced by
the quadriceps, which pull from the front. The hamstrings finish their work, with help from the
adductors and glutes, by straightening out, or "extending," the hip.
In a partial squat, which fails to provide a full stretch for the hamstrings, most of the force
against the tibia is upward and forward, from the quadriceps and their attachment to the front of
the tibia below the knee. This produces an anterior shear, a forward-directed sliding force, on the
knee, with the tibia being pulled forward from the patellar tendon and without a balancing pull
from the opposing hamstrings. This shearing force — and the resulting unbalanced strain on the
prepatellar area — may be the biggest problem with partial squats. Many spectacular doses of
tendinitis have been produced this way, with "squats" getting the blame.
The hamstrings benefit from their involvement in the full squat by getting strong in direct
proportion to their anatomically proper share of the work in the movement, as determined by the
mechanics of the movement itself. This fact is often overlooked when considering anterior
cruciate tears and their relationship to the conditioning program. The ACL stabilizes the knee: it
prevents the tibia from sliding forward relative to the femur. As we have already seen, so does the
hamstring group of muscles. Underdeveloped, weak hamstrings thus play a role in ACL injuries,
and full squats work the hamstrings while partial squats do not. In the same way the hamstrings
protect the knee during a full squat, hamstrings that are stronger due to full squats can protect the
ACL during the activities that we are squatting to condition for. In fact, athletes who are missing
an ACL can safely squat heavy weights, because the ACL is under no stress in a correctly
performed full squat (fig. 2-5).
Another problem with partial squats is the fact that very heavy loads may be moved, due to
the short range of motion and the greater mechanical efficiency of the quarter squat position.
This predisposes the trainee to back injuries as a result of the extreme spinal loading that results
from putting a weight on his back that is possibly in excess of three times the weight that can be
safely handled in a correct deep squat. A lot of football coaches are fond of partial squats, since it
allows them to claim that their 17 year-old linemen are all squatting 600 lbs. Your interest is in
getting strong (at least it should be), not in playing meaningless games with numbers. If it's too
heavy to squat below parallel, it's too heavy to have on your back.
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