Starting Strength, 3rd Edition - Mark Rippetoe [80]
Figure 4-31. The effect of different variations of back and leg dimensions on the back angle in the starting position. From left to right, back length increases as leg length decreases.
Most of the problems you will have with deadlift form can be analyzed with a good understanding of pulling mechanics. Consider, for example, the problem of lowering the bar with a round back, caused by unlocking the knees first: the down phase is the exact reverse of the pull. If the last thing that happens at the top of the deadlift is the simultaneous extension of knees and hips, with a locked back and the chest up, then the first part of lowering the bar has to be knee and hip “un-extension” with a locked back and the chest up (Figure 4-32). The knees unlock just enough to take the tension off the hamstrings, at exactly the same time that the hips unlock. Then the butt travels back with the lower back locked, as the lifter closes the hip angle and uses the hamstrings and glutes eccentrically as they lengthen. As the bar slides down the thighs, further closing the hip angle, it reaches a point as it passes the knees where the knee angle can begin to close with the hips. As the bar is lowered past the knees, they bend and the quadriceps add to the hamstrings’ eccentric function, and the bar gets to the floor. This sequence of movements – the opposite of the pulling-up sequence – allows the bar to drop down in a vertical line (Figure 4-32).
Figure 4-32. The correct down sequence is the opposite of up (Figure 4-28). The last thing that happens on the way up is the first thing that happens on the way down: the hips and knees unlock simultaneously; then the hips move back and lower the bar to below the knees; then the knees flex and lower the bar to the floor.
Any deviation from this order will not work. If your knees move forward first when you are lowering the bar, they will be in front of the bar, and the bar cannot go straight down because it has to go forward to get around the knees (Figure 4-33). Your knees can move forward only so far before your heels get pulled up, so you round your back to let the bar go forward far enough to clear your knees. This action places the bar off-balance, forward of the mid-foot. If you find yourself progressing forward across the floor from the start to the finish of a set of five, this is why.
Figure 4-33. This is the wrong way to set the bar down. The knees have moved forward first, and this places them in a tragic position where kneecaps often pay a high price. And if the kneecaps somehow remain unscathed, the lower back might not.
As you pull the bar off of the floor, your knees and hips extend together while your back angle stays constant, meaning that the quads initiate the push off the floor while the hamstrings hold the back angle constant, resulting in an opening of the knee and hip angles. If you attempt to extend your hips first, the result will be a non-vertical bar path. This happens when you lift your chest first, thus opening the hip angle first and leaving the knee angle in the start position. If this happens, the bar goes forward around your knees, which have not pulled back out of the way. This actually occurs only with very light weights; heavy weights like to move in straight vertical lines. If you try to pull heavy weights chest-first, you will be dragging the bar back into your shins, and the blood on the bar will tell you this is wrong. And when it’s very heavy, the bar will not travel forward around your knees anyway because you can’t pull a heavy weight off-balance forward.
When the knee angle opens first, as it should,