A stupid question about the deadlift?

[Instinctkiller]

Hello Rip

I understand why the lats pull the humerus best at 90 degrees and I understand why we want to pull the bar close to the body over the mid-foot. I really understand why the lats are stronger in the 90 degree angle position. I just can't figure out what the hell pulls the bar forward, with such force that our LATS can't pull it backwards with the same force if they don't have the best moment possible. What pushes it forward that if we won't pull it backwards it will just move ahead?
I mean, we pull the bar up. I use my anterior deltoid to push it away from my body. I apply force only upwards. I think so.

Can you solve that (stupid, I guess) mystery to me?


Thanks Rip.

[Mark Rippetoe]

This is not really a stupid question, as I think you know. It's actually very good. The fact is that the bar can indeed be held in position against the legs by the lats at any lat angle of attack on the humerus if the weight is light enough. And by lat angle we actually mean the back angle, since the back angle controls this if the bar is over the mid-foot -- see figure 4-26 in BBT3. So the question is, why does this particular back angle -- the position that places the lats at about 90 degrees to the humerus, with the shoulders slightly in front of the bar and the bar over the mid-foot -- establish itself at the point of pull in every heavy deadlift, no matter what back angle you try to use (http://www.youtube.com/watch?v=eCwN6IANWNM is a very good example)?

The answer is, I don't know for sure, and I don't know anybody else other than me and my staff who has even considered the question or discussed the phenomenon. And my explanation has changed a couple of times over the past few years, as I've thought about it and discussed it more. I THINK that what's happening is that in a deadlift, more of the mass of the lifter is behind the mass of the bar, and as the weight goes up the ability to control the position of this mass becomes more critical. Since the direction of equilibrium for the body's mass in relation to the bar's position is more forward, the hips rise and the back angle becomes more horizontal to rotate the torso into this position. Lat strength and efficiency is tested in this position because if the arms hung straight down vertically, the bar would drift forward of mid-foot, pulling the lifter off-balance and rearranging the mass distribution relative to the bar. So the lats stabilize the system in balance at heavy weights, and as the weight gets lighter the more divergence from this model the pull can tolerate. The bar must obviously travel upward in a straight vertical line, and the lats function to control this position of shoulders forward of the bar until almost the top of the pull, where the arms finally get vertical. We don't see this happen in a clean or snatch, for obvious reasons.

So essentially, nothing is pushing the bar forward. You just can't pull it from any position other than back when it's heavy enough. When it's light, you can do anything you want to with it. There are other factors we will discuss as the questions start rolling in.

[Robert NL]

If the back angle becomes more horizontal the lat angle increases thus more of the barbell mass is is loaded on the lats. The lats attach much lower on the back than the arms do. The moment arm from the lats to the hip is much shorter than the moment arm of the arms(shoulder) to the hip joint. So the larger percentage of the weigth the lats carry the easier the lift gets on the hamstrings and lower back.

to illustrate
deadlift.jpg
damn I just cant get those pictures to attach how i want. Anyway..

If you divide the load of the Barbell along the arms and the lats it should be obvious that the second lifter has a much bigger portion of the load going through the lats to the spine. Thus increasing mechanic efficiency.

Could it be that a more horizontal back, thus more of the load on the lats, is the only way the spine can cope with the bigger weight? If the load is hanging from the shoulders only the back is used as one long lever. If a portion on the weight is on the lats the load get distributed along a much bigger part of the spine.

[OCG]

Bonus round: Rip, how does the fact that as the bar passes the knee the shins have to be vertical, or very close to vertical, to allow the bar to pass and keep moving in a straight line play into this?

[Mark Rippetoe]

If the back angle becomes more horizontal the lat angle increases thus more of the barbell mass is is loaded on the lats. The lats attach much lower on the back than the arms do. The moment arm from the lats to the hip is much shorter than the moment arm of the arms(shoulder) to the hip joint. So the larger percentage of the weigth the lats carry the easier the lift gets on the hamstrings and lower back.

to illustrate
deadlift.jpg
damn I just cant get those pictures to attach how i want. Anyway..

If you divide the load of the Barbell along the arms and the lats it should be obvious that the second lifter has a much bigger portion of the load going through the lats to the spine. Thus increasing mechanic efficiency.

Could it be that a more horizontal back, thus more of the load on the lats, is the only way the spine can cope with the bigger weight? If the load is hanging from the shoulders only the back is used as one long lever. If a portion on the weight is on the lats the load get distributed along a much bigger part of the spine.

These pictures are wrong, refer to my figure 4-26. The first configuration will not leave the floor like this, and the 2nd probably won't either. And all of the weight the lats carry is born by the back segment.

Bonus round: Rip, how does the fact that as the bar passes the knee the shins have to be vertical, or very close to vertical, to allow the bar to pass and keep moving in a straight line play into this?

The knees are out of the way when the bar passes them in a vertical line. They rebend for a clean/snatch, they don't for a deadlift. What do you mean, how does it play into this?

[OCG]

The knees are out of the way when the bar passes them in a vertical line. They rebend for a clean/snatch, they don't for a deadlift. What do you mean, how does it play into this?

Well, if the knees must be out of the way for the bar to pass, and I'm fairly sure they must, then this will effect back angle. If the knees must be in a certain position with the hands in a certain position (at knee level) then of course this will effect the position of the femurs and hips, which will effect the back angle. It seems to me, though of course I may be wrong, that there is a very little variation in back angle possible whilst holding your combined COG over your midfoot with near vertical shins whilst holding your straight arms by your knees.

I hope this makes sense Rip, I'm kind of tired and doing free body diagrams in my head then typing them out is taxing to my current mental capacities.

[Savs]

I may be wrong, but I'm reading this as two questions.

Instinctkiller's question about what pulls the bar forward is, I believe, answered in detail in BBT3. Gravity pulls it forward since the arms aren't vertical. As Rip has done, treat the arm as a rod connected to a shaft at the shoulder. The bar will swing forward (to a point directly under the shoulder) unless the lats hold it back (balance the moment about the shoulder). I think BBT3 also explains moment (torque) very nicely, and makes the point that the lats act at 90 deg to the humerus because the torque is greatest at 90 deg (where the sine of the angle is 1).

Rip's question is puzzling! I have no answers, just more questions. Rip, is the body's COM really behind the center of the foot (which I'll shorten to "center") when the bar breaks the floor? The most efficient pull is when the bar travels a vertical path over the center; therefore, the bar's COM is always over center. Shouldn't the total system's (bar + body) COM also always be over center? If so, since the bar is always over center, the body's COM must also be over center and that means the head and shoulders (along with a little of the knees) have to go forward of center.

You seem to be arguing here that the total system's COM does not start over center. If the body's COM is behind the bar to start, when the bar breaks the floor, how does the lifter remain standing? Can the muscles of the foot and lower leg keep the lifter from toppling if the system's COM gets "far" from over center? (Maybe you're saying it isn't that far, the moment isn't so great.) Are you saying that the momentum from the body's COM moving toward the bar (toward center) somehow contributes to the vertical portion of the pull?

I want to believe that the total system's COM must be over center when the bar breaks the floor; however, I don't know if my belief is correct. The truth is whatever is shown by heavy deadlifts - the experiment (done many, many times).

[Splat]

The knees are out of the way when the bar passes them in a vertical line. They rebend for a clean/snatch, they don't for a deadlift. What do you mean, how does it play into this?

This has always bugged me when I start thinking about the deadlift too much. I can be a little dense about some things perhaps. Anyway, how does the weight stay in contact with your legs if it is moving in a vertical line given the thighs are not yet vertical?

[vkp78]

At the particular point when we need the lats the most to keep the bar to the shin, is it not possible that the pecs are pulling the humerus forward?

[Mark Rippetoe]

Well, if the knees must be out of the way for the bar to pass, and I'm fairly sure they must, then this will effect back angle. If the knees must be in a certain position with the hands in a certain position (at knee level) then of course this will effect the position of the femurs and hips, which will effect the back angle. It seems to me, though of course I may be wrong, that there is a very little variation in back angle possible whilst holding your combined COG over your midfoot with near vertical shins whilst holding your straight arms by your knees.

Okay.

Rip's question is puzzling! I have no answers, just more questions. Rip, is the body's COM really behind the center of the foot (which I'll shorten to "center") when the bar breaks the floor? The most efficient pull is when the bar travels a vertical path over the center; therefore, the bar's COM is always over center. Shouldn't the total system's (bar + body) COM also always be over center? If so, since the bar is always over center, the body's COM must also be over center and that means the head and shoulders (along with a little of the knees) have to go forward of center.

The COM that counts is that of the lifter/barbell system, since both move together. I think that at light weights, the COM is behind the barbell, but the tendency to move toward the standard pulling position is in operation. The mechanism that you note regarding the bar swinging forward will not operate if the hips are too low and the arms hang vertically, but as the weight goes up and the COM of the system begins to approximate that of the barbell, hips will rise and shoulders will go forward to the best back angle for lat control of the swing.

You seem to be arguing here that the total system's COM does not start over center. If the body's COM is behind the bar to start, when the bar breaks the floor, how does the lifter remain standing? Can the muscles of the foot and lower leg keep the lifter from toppling if the system's COM gets "far" from over center? (Maybe you're saying it isn't that far, the moment isn't so great.) Are you saying that the momentum from the body's COM moving toward the bar (toward center) somehow contributes to the vertical portion of the pull?

I don't understand this, sorry.

This has always bugged me when I start thinking about the deadlift too much. I can be a little dense about some things perhaps. Anyway, how does the weight stay in contact with your legs if it is moving in a vertical line given the thighs are not yet vertical?

Your lats keep it there.

At the particular point when we need the lats the most to keep the bar to the shin, is it not possible that the pecs are pulling the humerus forward?

No.