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tighten. Likewise, lifting the chest requires a contraction of the upper back muscles, especially the superior portion of the longissimus dorsi complex. Lifting the chest is thoracic spinal extension, a back movement. The act of tightening the shoulders and lifting the elbows aids the thoracic extension muscles by helping to support the bar at the point where it is mashing down into the back. If you do both of these things at the same time, all the muscles under the bar tighten. And if you do this before you take the weight of the bar onto your back, the bar cannot sink down through loose muscle, unsupported against the skeletal components of the shoulder. Lifting the elbows and the chest together tightens the supporting muscles under the bar, so do this before you let the weight bury itself in your back.

Many people seem to be making a flat, level spot for the bar to sit on by keeping their chest parallel to the floor. It is as if they think that bending over into a position of spinal flexion makes the bar less likely to roll off the back. The bar will not roll off your back if you properly grip the bar, with your hands in the right position, and raise your elbows. When the elbows come up and the chest comes up, the hands are pushed forward and the bar is actually forced forward into the back, trapped between the hands and the rack position, so it cannot go anywhere. This jamming effect creates a tight, secure bar position that can tolerate changes of angle, acceleration, and deceleration.

Back

Although the squat has an undeserved, baseless reputation for knee injury, its greatest danger is to the spine. Lower-back injuries – usually due to form problems – are more common by far than knee injuries, and care must be taken to prevent them. It’s not hard to hurt your lower back, and back injuries are the most common workplace injury, amounting to many billions of dollars per year in treatment costs and lost productivity. Lifters are susceptible as well, although our problems with lower-back injuries are most often associated with activities outside the gym. We know this because hundreds of thousands of young lifters at the mercy of inexperienced, pigheaded coaches are permitted to lift heavy weights with bad spinal mechanics every day, and the rate of injury in the weight room remains low. The most dangerous movement for the spine is flexion with rotation under a load, and we don’t do this in barbell training – we do it when putting the lawn mower in the back of the truck. So barbell training, even done incorrectly, is comparatively safe. But doing it wrong is much more dangerous than doing it correctly. Our primary concern is that doing it wrong is also inefficient, so we’ll do it right because that ultimately allows us to lift more weight and get stronger, and safety will be a welcome side effect.

Understanding the role of the lower back in lifting mechanics requires an understanding of the anatomy of the hip and leg musculature, as well as of spinal anatomy. Remember from our previous discussion that the spine acts as a rigid bar to transmit moment force generated by the muscles that extend the hips and knees. The spine is held rigid by the musculature of the trunk, and it is moved through space by the muscles that extend the pelvis, into which the spine is locked by the muscles of the low back.

The hamstring group consists of the biceps femoris, the semimembranosus, and the semitendinosus, all three of which attach to the ischial tuberosity of the pelvis. They all insert at various points on the tibia, behind the knee on the lower leg. This configuration means that the hamstring group crosses two joints, the hip and the knee, and therefore technically has two functions: the proximal function (hip extension), and the distal function (knee flexion). The hamstrings can also act isometrically against both attachments to control the back angle.

Figure 2-35. (A) The relationship of the bones of the lumbar spine, pelvis, femur, and upper tibia and the actions of the muscles that move them, in profile. The squat