08-30-2007, 03:17 PM
I take "Starting Strength" to all the seminars that I teach and I strongly recommend it to all the students. At a seminar in Denver this past weekend a student, who had a copy of "Starting Strength" with him, had an interesting question. He discussed your explanation of the importance of "Going Deep" in the squat and that partial squats are ineffective due to the omission of the hams/glutes assistance. We certainly agree. His Question: "Does the rationale that partial squats are ineffective not apply to the deadlift which involves a partial squat?" Thanks so much for your take on this one.
08-30-2007, 11:11 PM
Now THAT is a damned interesting question. There are obviously differences in the positions of the two lifts, and in their very nature -- the deadlift starts concentric and finishes eccentric, while the squat starts eccentric and then uses a stretch reflex/viscoelastic rebound to initiate the concentric phase. But the glutes/hamstrings do a different job in the two lifts also. The rebound out of the bottom in the squat is due to adductors/glutes/hamstrings immediately opening up the hip angle along with the quads opening the knee angle from a below-parallel position.
In a deadlift, the higher starting position finds the quads in a much better mechanical position to initiate the push against the floor, and the job of the hamstrings is different; they have no rebound function at all, but rather "anchor" the pelvis in position so that the back angle -- the angle the plane of the back makes with the floor -- can stay the same so that when the quads extend the knees all the force gets to the bar. If the back angle changes, as it will if the chest does not stay up, the quads straighten the knees but the bar doesn't move up, so they have done no work. The hamstrings pull against the ischial tuberosity of the pelvis , and together with the rigid spine produced by the erector spinae, allow the force of the knee extension to move the bar up from the floor.
This is a much different function than the hamstrings have during the squat, partly due to the different position (depth) and partly due to the differences in initial contraction (eccentric/concentric).
But his question involves the differences in half-squat and deadlift. The deadlift can be a nearly pure hamstring/glute contraction if the knees extend without pushing the bar away from the floor, forcing the hip extensors to pull the entire load from the floor without the quads. The deadlift starting position is, in fact, about the same depth as a half-squat, so why no hamstrings/glutes in a half squat? Well, it's not that there is NO posterior chain in a half squat, it's that the quads are so predominant that they leave the glutes/hamstrings inadequately trained and the knees inadequately protected. The initial downward motion in a squat that gets cut off high is typically a knees-forward motion, with very little or no posterior track for the hips that would tighten the glutes/hamstrings and place them in a position where they can be used. This standard leg-press style half squat loads the knees so much more than the hips that it effectively eliminates the posterior chain from the movement, since sufficient depth that would otherwise make the posterior chain engage when the hips moved back is never obtained. Depth in a squat is always dependent on the hips moving back, since you can slide your knees forward until they touch the ground without ever dropping below parallel. Unless the hips move back and the hip angle changes enough, the hamstrings and glutes don't extend, and if they don't extend they can't contract.
A trained powerlifter that knows how to do a correct high-box squat can fix this by using hips down to the box the same way they would be in a deep squat, merely letting the box interrupt this correct squat above parallel. But this is not the same thing as a typical half squat at all, which is mostly quads. In fact, a powerlifter that cuts off a squat unintentionally is actually doing something more like a goodmorning, which is a predominantly posterior chain-based exercise. So the amount of posterior chain involvement in a squat is entirely dependent on the position of the hips when it is being done.
In contrast, a deadlift -- even a correct one that uses quads off the floor -- inherently incorporates so much hamstring and glute that it is one of the best exercises in the weight room specifically for that muscle group.
Hope this helps, thanks for the question.
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