Starting Strength

completely unnecessary if the bar starts out in balance with the body’s preferred position of pulling equilibrium so that a vertical bar path can be produced.
    The non-vertical arm angle is perhaps the most poorly explained phenomenon in weightlifting. Why does the back angle become stable for the first part of the pull when the shoulders are in front of the bar and the arms assume their characteristic angle of 7–10 degrees from vertical? Why is there an apparent equilibrium between how far the shoulders are in front of the bar and how far the hips are behind the bar? Our working theory is that the critical relationship is the interaction between the lats, and the teres major, the triceps, and the humerus. There is a back angle at which the lats can best stabilize the arms and shorten the distance between bar and hips in order to facilitate a vertical bar path, and a heavy deadlift settles into this angle because it cannot do otherwise.
    The humerus is suspended from the scapula by lots of muscle and ligament, and it would seem as though the arms should just hang vertically, as a weight on the end of a rope hanging from the ceiling hangs vertically, or “plumb” as it is called. But the arms don’t hang vertically, not with a weight that is actually heavy enough to force you to tighten your back and arms. Check the videos yourself. If you want that rope to hang from the ceiling at any angle other than vertical, you will have to apply another force to the system from a different direction – you’ll have to tie another rope to the one hanging plumb. And that second rope will work best against the first one if you pull at a right angle to the loaded rope, because a right angle is the configuration that allows the force to be applied most efficiently. Like pulling on a wrench at any angle other than 90 degrees, pulling on the rope from anything other than a right angle fails to generate the maximum turning force. It’s easier to see this when the first “rope” is your humerus, and the second rope is your lat.
    So, there is another rope after all; there are actually several of them. The teres major and the triceps control the angle between the scapula and the humerus. The teres major connects the inferior part of the scapula to the proximal end of the humerus on the anterior side, only millimeters away from the lat attachment under the armpit on the arm side. The triceps attaches the superior scapula, up high on the shoulder side of the armpit, to the elbow, although its leverage position is weak. More important, the lats connect their large origin along the low back directly to the shaft of the humerus, up under the armpit on the anterior side, so it pulls across the full thickness of the shaft. These muscles add to the large number of attachments from the shoulder joint area, which, working together, transfer force from the trunk to the arms.
    This posterior pull is responsible for the non-vertical angle of the arms as they hang from the shoulders under a loaded spine, and must equal the tendency of the weight to rotate the arms forward to a vertical position. If the arms rotate forward, this will place the bar forward of the mid-foot and thus off-balance, unable to be pulled if it is heavy enough. Since the triceps and the teres major are actually minor contributors to the situation due to their poor positions of leverage, the total contribution of the lats, teres major, and triceps averages out to approximately the same as just the lats. When the shoulder is in front of the bar and the back angle is stable in a pull, the angle of attachment between the lat and the humerus is about 90 degrees, since this is the angle at which the least muscular force is required to produce a rotation force that is equal and opposite to the weight . It is the angle at which these muscles can exert their tension on the humerus most efficiently and thus provide the maximum force transfer and stability during a pull from the floor in which the bar needs to stay over the mid-foot and as close to the hips as this stable “hang” will allow (see Figure 4-25 ). And the back angle adjusts to produce the 90-degree lat angle in equilibrium between the shoulders and hips.
    The fact that several muscles are contributing to this posterior pull makes the angle hard to calculate precisely, and some variation with anthropometry would be expected, but the lats appear to be the major factor in the system, and the angle of attachment in a