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

[spacediver]

I've been experimenting with different grip widths in the press, and have been thinking more about the way grip width affects things.

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.

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?


for reference:

[OCG]

1. It's one of those practical things. If you want to stick your elbows forwards, doing so with a wide grip excessively externally rotates the shoulder.

2. Straight from hand to shoulder isn't how you would calculate the torque on the shoulder. Off the top of my head, maybe end of the humerus to the shoulder would be close enough. Would also explain why the press starts easy, gets hard around halfway when the humerus is stuck out the furthest and then gets easy again towards the top.

[spacediver]

2. Straight from hand to shoulder isn't how you would calculate the torque on the shoulder. Off the top of my head, maybe end of the humerus to the shoulder would be close enough. Would also explain why the press starts easy, gets hard around halfway when the humerus is stuck out the furthest and then gets easy again towards the top.

But the force is being applied through the hand. So it would have to be the distance between hand and shoulder joint, no? When the elbows are flared out halfway up, that increases the moment arm at the elbow joint, which means triceps have to work harder.

1. It's one of those practical things. If you want to stick your elbows forwards, doing so with a wide grip excessively externally rotates the shoulder.

I understand that sticking your elbow forwards will externally rotate the shoulder, and that this may impact the lift. But in my mind, sticking the elbow forwards is what allows you reduce the moment arm, along the sagittal axis, between hand and glenohumeral joint. Is this what you meant?

[spacediver]

just so we're on the same page here, here is a diagram of a 2D representation of the situation in the frontal plane. The green squares indicate the hands. b is the moment arm between hand and shoulder joint, and a is moment arm between hand and elbow joint. These moment arms are along the frontal axis.

Here you can see the elbow is flared out, but because b is very small, the shoulders do very little work. In fact, if the hand was directly over the shoulder joints, you can see how any counterclockwise torque at S2, by itself, would contribute no upwards displacement of the bar.

[Tiedemies]

just so we're on the same page here, here is a diagram of a 2D representation of the situation in the frontal plane. The green squares indicate the hands. b is the moment arm between hand and shoulder joint, and a is moment arm between hand and elbow joint. These moment arms are along the frontal axis.

Here you can see the elbow is flared out, but because b is very small, the shoulders do very little work. In fact, if the hand was directly over the shoulder joints, you can see how any counterclockwise torque at S2, by itself, would contribute no upwards displacement of the bar.

You have to take into account how the E2 (symmetrically for E1) mediates the force.The muscles that rotate S2 to elevate E2 do of course work against the torque of b, but that is only the static view; for every millimeter the bar moves up, the muscles that extend E2 do some work, but the muscles that rotate S2 have to do a proportionate amount of work as well. if you trace the trajectory of E2, the moment arm a diminishes, then reaches zero, and slightly increases (to the other direction) near the top position. The moment arm of b remains static.

If b is zero, then the moment arm of a reaches zero at the top. Be that as it may, I don't think the muscles that rotate S2 do zero work,or, indeed, even any less work if b is minimized. I can't formulate this mathematically right now, but I am sure you can derive it by assuming a force that only opens the E2 angle. Obviously such a force cannot elevate the E2 point, so you will need a force/torque that simultaneously rotates the S2 angle.

[spacediver]

Tiedemes, in the following image, the green dot, C, represents a point mass exerting a downward force due to gravity. Torques are generated at A and B, and together, they cause C to move up in a straight line until the contraption is fully extended. Assume that C remains directly above A for the entire time, and that the "limbs" are massless. Do you agree that no work is required at A? I wanna double check that we're on the same page here, before responding to your post.

If you're uncomfortable with massless limbs, then assume the limbs have a mass. In that case, the torque required at A is simply the integral of the (mass at any point along the limbs * the horizontal distance between that point and A). But importantly, do you agree that in this case, that the mass at C has no bearing on the work done at A?

[OCG]

So if we take your equation to it's logical conclusion, if the hand is directly above the shoulder then the moment arm on the shoulder is zero, and there is no significant torque on the shoulder? So, then why can't we press a ridiculous shittonnne of weight just by moving our grip in?

As far as external rotation, as we move the grip wider, the external rotation required to get the elbows forwards become quite excessive and potentially injurious. Try this, gently, take a very wide grip, say pointers on the rings. Now, stick your elbows as far forwards as possible. See what happens.

[spacediver]

So if we take your equation to it's logical conclusion, if the hand is directly above the shoulder then the moment arm on the shoulder is zero, and there is no significant torque on the shoulder? So, then why can't we press a ridiculous shittonnne of weight just by moving our grip in?

Because now the triceps have to do all of the work. That's the whole point of my question - whether instead it makes more sense to instead distribute the load optimally (as we do between quads and hammies in the squat).

As far as external rotation, as we move the grip wider, the external rotation required to get the elbows forwards become quite excessive and potentially injurious. Try this, gently, take a very wide grip, say pointers on the rings. Now, stick your elbows as far forwards as possible. See what happens.

Yes, I don't disagree with this, and I can see how this is important to consider when choosing a grip width.

[Tiedemies]

Tiedemes, in the following image, the green dot, C, represents a point mass exerting a downward force due to gravity. Torques are generated at A and B, and together, they cause C to move up in a straight line until the contraption is fully extended. Assume that C remains directly above A for the entire time, and that the "limbs" are massless. Do you agree that no work is required at A? I wanna double check that we're on the same page here, before responding to your post.

If you're uncomfortable with massless limbs, then assume the limbs have a mass. In that case, the torque required at A is simply the integral of the (mass at any point along the limbs * the horizontal distance between that point and A). But importantly, do you agree that in this case, that the mass at C has no bearing on the work done at A?

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.

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 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.

[Nate7out]

Other threads that discussed this directly or tangentially:

press narrow grip vs. wide grip

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