press question. Is reduced moment arm between hand and shoulder a good thing?

[spacediver]

Well, work, not, but *torque* is needed at point A nevertheless. Consider point A as frictionless hinge-point, and consider that firstly, point B is completely rigid. Now, the system is in balance. However, when torque is applied at point B,
this will move point A also horizontally; if point A were completely rigid, then the mass at C could not move vertically at all. So, torque is needed at point A to balance the point C above point A.

Rotation is definitely needed at point A, but I still don't see how torque is needed at A.

Consider this. If the contraption was motionless to begin with, and then started extending so C rises upwards, there will have been no change in angular momentum around A (assuming limbs are massless). This means that the net torque at A must be zero. Which means that if a counterclockwise torque was experienced at A, it would have to be balanced by a clockwise torque at A. But I don't see any way a clockwise torque could occur at A.

If I understand you correctly, are you saying that a clockwise torque generated at B can cause a counterclockwise rotation at A? If so, I agree (see links at bottom of this post).

This argument will eventually degenerate to something that is equivalent to the claims that the squat doesn't train your abs because they don't do work (they don't, technically).

I don't think I'm making quite the same style of argument here. Yes, when the spine is held rigid in the squat, the net torque around each facet joint is zero. But the abs and spinal erectors still have to generate a "moment of extension" to counteract the "moment of flexion" generated by the bar. Perhaps work is the wrong term to use in this thread.

I can make an analogous argument; Consider that point C is fixed so that it cannot move horisontally. Point A on the other hand is a free hinge point with no forces. Then, applying torque only to point A will cause the point C to rise. So, no work is needed at point A either.

If point C was constrained to move only vertically, that would mean that there would be constraint forces acting at C that had a horizontal component. In your example, these forces would act rightwards at C, and create a clockwise torque around B, resulting in an upwards displacement of C. But without constraint forces, I don't see how a counterclockwise torque at A can produce upward displacement of C (I'm not being stubborn, I really want to understand your point).

btw, this algodoo simulation I created, which shows how torque generated by the glutes can achieve dorsiflexion, might be relevant (inspired by this thread).

[spacediver]

Other threads that discussed this directly or tangentially:

press narrow grip vs. wide grip

Bones Morphology Influence on Overhead Pressing - A question for Ripp'

Thanks. I'd seen the first, but not the second. I don't think either addresses the exact question I'm asking, but as you say, they are tangentially related.

[Daverin]

If our goal is to press as much weight as possible above our heads, shouldn't the goal be to optimally balance the work requirements between elbow extensors and shoulder abductors & flexors, rather than to minimize the burden on the shoulder musculature?

I don't know, is it? It is kind of telling that the push press allows so much more weight because it gets you out of the hole where the shoulders are generally considered most taxed, and now the triceps are brought closer to a challenging load while the shoulders are in a much better position to help. Sure enough, it is also advisable to take a wider grip than your press, both to maximize distance accrued from the push, and otherwise shorten range of motion (And actually get that even moment now that the shoulders are "caught up.")

Arguably, the narrow grip is what allows for the shoulders to have the most advantage at the start, which I think is borne out by how the narrow grip is more likely to produce a stall around forehead height, whereas a "medium" or wide grip comes closer to the outright start. Which means you now have some momentum you can build coming to the sticking point.

Strangely enough, by this argument, I would almost think that the hip bow of the press 2.0 would actually allow for a wider grip to be more advantageous since you theoretically now can build speed and have a more even moment distribution (aka dem vertical forearms under bar.) Yet, if anything, I tend to feel a medium grip works well strict, but I reaallllyyy prefer narrow if I use any hip motion.

I still haven't figured it out myself. And to top it off, I have come to notice that jamming my elbows forward and even letting the bar rest slightly back in my hands makes the start quicker, and then around forehead or above head height I rotate my elbows under the bar and get it back onto the meat of my palm. Between this and my obsessive history adventure with the Olympic Style press, I have come to the conclusion that the press is just weird, and benefits from weird things. YMMV.

[spacediver]

I don't know, is it? It is kind of telling that the push press allows so much more weight because it gets you out of the hole where the shoulders are generally considered most taxed, and now the triceps are brought closer to a challenging load while the shoulders are in a much better position to help. Sure enough, it is also advisable to take a wider grip than your press, both to maximize distance accrued from the push, and otherwise shorten range of motion (And actually get that even moment now that the shoulders are "caught up.")

Are the shoulders considered the most taxed at the bottom of the lift because the muscle fibers are at their longest (i.e. is it a length-force issue?)

I still haven't figured it out myself. And to top it off, I have come to notice that jamming my elbows forward and even letting the bar rest slightly back in my hands makes the start quicker, and then around forehead or above head height I rotate my elbows under the bar and get it back onto the meat of my palm. Between this and my obsessive history adventure with the Olympic Style press, I have come to the conclusion that the press is just weird, and benefits from weird things. YMMV.

heh, yea I'm enjoying the experimentation myself. Hardest part is controlling for other variables (inter set fatigue being a big one).

[Tom Campitelli]

If we were to actually completely eliminate the moment arm between hand and shoulder joint (along both the frontal and saggital axes), and maintain this throughout the entire movement, this would mean that the muscles that produce torque around the shoulder joint do zero work. Rather, the entire burden is left to the elbow extensors (tricep) and a small amount to the traps.

Aside from the fact that this is not possible, what muscles flex the shoulder? That would still have to happen even if you could get your hands right over the shoulder joint.

[spacediver]

Aside from the fact that this is not possible, what muscles flex the shoulder? That would still have to happen even if you could get your hands right over the shoulder joint.

If you were to hypothetically get your hands right over your shoulders, the shoulders would need to flex to keep the bar going in a straight line, but the muscles wouldn't be experiencing any resistance from the barbell. The only resistance they'd experience would be due to the weight of the forearm and upper arm. Torque generated by the triceps at the elbow joint would also also contribute to shoulder flexion, in the same way that the glutes can straighten out the hips.

It's the same in the squat. If the barbell is directly over the knee joint, there is no moment arm at the knee joint, and the quads don't feel any resistance of the barbell. In that situation, the hip extensors bear all the load.

[Toasterleavings]

If you were to hypothetically get your hands right over your shoulders, the shoulders would need to flex to keep the bar going in a straight line, but the muscles wouldn't be experiencing any resistance from the barbell. The only resistance they'd experience would be due to the weight of the forearm and upper arm. Torque generated by the triceps at the elbow joint would also also contribute to shoulder flexion, in the same way that the glutes can straighten out the hips.
It's the same in the squat. If the barbell is directly over the knee joint, there is no moment arm at the knee joint, and the quads don't feel any resistance of the barbell. In that situation, the hip extensors bear all the load.

Would the shoulders really experience no resistance? Imagine you can assume the hypothetical position. With nothing else doing anything else but supporting that static hold, contract your triceps in your imagination. Where does the bar go? Now imagine picking up the bar from where you forcefully threw it onto the ground in front of you.

[spacediver]

Would the shoulders really experience no resistance? Imagine you can assume the hypothetical position. With nothing else doing anything else but supporting that static hold, contract your triceps in your imagination. Where does the bar go? Now imagine picking up the bar from where you forcefully threw it onto the ground in front of you.

Yes, if you only contract your triceps, the bar is going to arc fowards. As I said, you have to flex the shoulders too to keep the bar moving vertically, but the resistance the shoulder will experience here is a function of the weight of the forearm and upper arm, not of the barbell. In other words, if you had a 10 pound barbell vs a 200 pound barbell, the shoulders will not be able to tell the difference.

Another way to think about this is the components of motion the barbell experiences due to shoulder flexion. If there is no moment arm (i.e. barbell directly above shoulder joints), then if you were to only rotate at the shoulder, the instant this happens, the barbell is experiencing a purely horizontal component of motion.

Think about a clock mounted on a wall, with a single hand that sweeps the circumference in a continuous fashion. At any given instant, the tip of the hand has a horizontal and vertical component, and this can be visualized as the tangent the tip makes with the circle it is tracing out. At 12 o clock, the tangent is a straight horizontal line - there is no vertical component.

In the press, the shoulder joint is the centre of the clock, and the tip of the hand is the barbell (the hand itself would be an imaginary line between the barbell and shoulder joint). When the moment arm between barbell and shoulder is zero, the hand is at 12 o clock.

Now clearly, to keep the bar moving in a straight line, we have to rotate around the shoulder and the elbow. But this thought experiment allows you to see the individual contribution of each joint.

[Tiedemies]

If point C was constrained to move only vertically, that would mean that there would be constraint forces acting at C that had a horizontal component. In your example, these forces would act rightwards at C, and create a clockwise torque around B, resulting in an upwards displacement of C. But without constraint forces, I don't see how a counterclockwise torque at A can produce upward displacement of C (I'm not being stubborn, I really want to understand your point).

btw, this algodoo simulation I created, which shows how torque generated by the glutes can achieve dorsiflexion, might be relevant (inspired by this thread).

Now consider that point C is the point at which a lifter grips the bar. The friction of the grip makes it impossible for the hand to move horizontally (let us assume a 2-D model here). The force of friction is always assumed to be exactly the same as the horizontal force that would move C to the left or to the right.

Apply counterclockwise torque at A, and C will rise even as point B is just a hinge/joint but no torque is generated there. Point C will rise. Analogously, if A is simply a hinge/joint with no torgue, applying clocwise torgue to B will cause point C to rise.

In a system where equal torque can be applied to *both* A and B, the net force lifting C will be greater than if you apply it only on one or the other. Introducing a moment arm may change how the torque applied to each point contributes to a force acting on C, but in any case, the force acting on C is some linear combination of the torques applied to A and B, and the coefficients of this linear combination depend on the possible moment arm between C and A.

What I am getting at is, that the *optimal* moment arm is such that allows for the muscles that do elbow extension and the muscles that rotate shoulder up to contribute maximally. This depends on antropometry (I.e. proportions of forearm/humerus) and muscle developement (the forces produced by trapezius et al, and triceps et al.)

As per training most effectively, that depends on basically how much muscle activation takes place. Theoretically a weaker triceps can be compensated for to some extent, but I doubt that that is how it works. Perhaps a "pathological" or unoptimal muscle activation pattern can be changed by changing grip-width so that the proportionate forces are different.

Also, I have noticed that for me personally, as I have some problems with external rotation and the AC-joint, a zero-moment arm -- in fact, a moment arm that is zero wrt the AC-joint, not the shoulder joint -- protects my shoulder. If I take a wider grip, then the AC joint gives me hell. So there is this consideration. And given that while training this way I do fatique my trapzZz and other shoulder-muscles, I seriously doubt that they would not contribute.

[Tiedemies]

By the way, Spacediver, I do not think you are stubborn. You are wonkish about these matters and I dig that. Some peole get tired of ironing out mechanical models.

The thing with this particular model is that the degrees of freedom of the system you described should be considered. If you have to hinge points, then torque on both contribute to the force at the end of the lever. Applying torque only on one, causes the force vector at C to have a non-zero angle against the resistance; this is suboptimal. The torques at (or actually, we should say "around", because the moment arm actually comes from the muscle attachment point some distance off the point of rotation) A and B must be such that the resultant force vector at C has a zero angle (or 180degrees, if you like) against the force vector on C produced by gravity, if C is to move vertically. If you impose a constraint (as the grip of the barbell does!) against horizontal displacement, then you can transfer the work between the muscles that act on A/B. Whether you do, you should feel this as a sideways "snag" in the grip, that offsets the horizontal force.

Mid you, by the way, that our model is a bit off in that the moment arms of the left and right arm resp. in the actual press are not coplanar; they point ahead of the torso; The wider the grip, the more flared the elbows are and vice versa, to the point where if you have the grip directly above the AC-joint, your elbows pretty much point forward; this eliminates the above argument, because the grip/friction that works against horizontal displacement is then perpendicular to the actual horizontal force. In this case, you *have to* produce a net resultant force vector that points directly up; if you don't, the barbell is pushed forward of the shoulder joint and you will miss the rep. (Your throat pretty much prevents you from producing a significant displacement in the other direction... )

From the above reasoning I conclude that it is perfectly plausible, and even probable, that the optimal training effect -- i.e., the use of as much weight over the maximal range of motion while activating the largest mass of muscles(*) -- is achieved by having the barbell directly above the shoulder joint.

(*) Of course as there are three criteria, not all are necessarily maximized at the same time. But what I mean is, if you introduce a moment arm, even if you may sometimes increase the muscle mass you activate, you probably don't move that much more weight and you do lose on range of motion, i.e., the tradeoff is bad. Minor variations due to antropometry are probable, and looking at the way people actually press, the variations are more likely in the direction of introducing a distal (away from the shoulder joint) moment arm. Very few (actually, can't think of any) people I have seen use a grip narrow enough to introduce a moment arm int he other direction. But I suspect the reason is not the one you conjectured in the opening, but rather related to the fact that the human body is not very accurately modeled with such simple mechanics.