Starting Strength, 3rd Edition - Mark Rippetoe [79]
Figure 4-28. The correct sequence off the floor. (A) The starting position. (B) Knees extend, opening the knee angle. (C) The hip angle opens, bringing the bar up to the finish position (D).
As the hips extend more, the hip extensors – the glutes, adductors, and hamstrings – become the predominant movers of the load, the quads having finished most of their initial job of extending the knees before the bar gets to them. The role of the back muscles during the pull is to hold the trunk rigid and keep the shoulder blades back in their normal anatomical position so that the force generated by knee and hip extension can be transferred up the back, across to the arms, and down to the bar. Lockout at the top occurs when the knees and the hips reach full extension simultaneously, with the chest up and the shoulders back. If this pulling sequence is followed, the bar will come up the legs in a vertical path.
If the back rounds during the pull, some of the force that would have gone to the bar gets eaten up by the lengthening erectors. If the weight is sufficiently heavy, the rounded back cannot be re-straightened and the deadlift cannot be locked out; the spinal erectors are designed to hold an extended position isometrically, not to actively extend a flexed spine under a compressive load. The knees and hips are already extended – the knees in this position are straight and the pelvis is in line with the femurs – and their extensors cannot help since they are already fully contracted.
Figure 4-29. A rounded lower back is difficult to straighten when the weight is heavy. The muscles that hold the lumbar spine in extension are postural and are not designed to change the relative positions of the vertebrae; their job is to maintain extension, not to concentrically extend under compressive loading. And if the spine is in flexion, the hips are, too. If the hip extensors have finished their job, the pull is essentially finished. The only way to continue the pull would be to “hitch” the bar with a knee re-bend that would allow the hip position to reset a little. Many heavy deadlifts have been missed this way.
The question of exactly what these three angles should be is answered for each person individually since it depends on individual anthropometry. People with long femurs, long tibias, and relatively short torsos will have a more horizontal back angle and a more closed hip angle than people with long torsos and short legs, who will have a more vertical back angle and a more open hip angle. Each person will have a different set of knee, hip, and back angles, but the correct starting position for everyone will have the previously discussed things in common: the shoulders will be slightly in front of the bar; and the bar will be touching the shins directly over the mid-foot, resulting in the vertical alignment of the scapula, bar, and mid-foot. If this alignment is correct, and if the arms are straight, the feet are flat on the floor, and the back is in good thoracic and lumbar extension, the resulting reference angles are correct for that person’s anthropometry. Of the three angles, the back angle will exhibit the most obvious individual variability, easily seen by an informed observer.
Figure 4-30. A comparison of different anthropometries in the deadlift start position.
Arm length must also be considered when you are analyzing these angles. All other segment lengths being equal, short arms produce a