Bent arm vs Straight arm planche

Hello everyone, 

My apologies if this has been asked in the past but I'm trying to figure out exactly why a bent arm planche is easier than straight arm.

I always thought the straight arm PL has a bigger torque on the shoulder, but after some trivial physics, it's easy to see the torque about the shoulder is equal to both.

So perhaps it's because of the whole "muscles exert the most force at their resting lengths"? And the straight arm planche places the biceps very lengthened,  so it becomes a lot harder? The difference is very large so it's hard to believe that's the entire reason! 0_o

the leverage on the anterior shoulders is higher on straigth arm planche. 

Also in the bent version the shoulder is supported bu chest and biceps.

38 minutes ago, Alessandro Mainente said:

the leverage on the anterior shoulders is higher on straigth arm planche. 

So you're saying the SA PL is easier? I don't think that's true.

What do you mean by the shoulders being supported? That might the real reason then.

Never said that, during the SA variation the horizontal component of the weight is definitely higher compared to the bent version. for this reason the effort perceived on the anterior shoulder is higher compared to the bent arm planche.

when I say supported I mean "helped" from chest , triceps and biceps.

17 minutes ago, Alessandro Mainente said:

Never said that

You said the SA PL has a higher leverage on the shoulders. This means it's easier because the less leverage you have, the harder something becomes. The secret to making an exercise harder is to decrease your leverage.

17 minutes ago, Alessandro Mainente said:

during the SA variation the horizontal component of the weight is definitely higher compared to the bent version. for this reason the effort perceived on the anterior shoulder is higher compared to the bent arm planche.

Could you explain exactly what you mean by "horizontal component of weight"? Weight is only a vertical force, no horizontal component so perhaps you mean something else? 

17 minutes ago, Alessandro Mainente said:

when I say supported I mean "helped" from chest , triceps and biceps.

Well but those muscles also work hard during the SA PL. I guess you're saying they help even more during the Bent-arm planche? 

Here, I drew the free-body diagrams, with the torques about the shoulder angle. I mainly ask because my friend asked me why the SA is so much harder and I immediately told him it was because of decreased leverage. But we're both Mechanical Engineering students, and he wasn't convinced. When we worked out the physics, it's pretty easy to see the leverage and torque is the exact same. So the answer must be somewhere else. Perhaps because it's much harder to balance?

Physics alone won't give you the answer. As Alessandro pointed out, you have to understand something about functional anatomy, how the body works as a whole, in motion or stillness.

You equations it is correct, I was confused since in some pl push up executions I noticed that at the end of a planche push up, D it is not the same . but I admitt that those cases are typical of the last planche push up where people tend to become fatigued. normally D is the same. if not:

1-the bent arm variation has its moment of rotation (i think you mean torque)  that could be expressed as M1 = Force₁ * the arm of force₁

2-the SA variation has its own MoR that could be expresses as M2 = Force₂ * the arm of force₂

In both cases the Force that you should "defeat" is the same bodyweigth .

We can now compare the 2 equations and you can see that in the first case the arm of the force is less compared to the SA variation (you made the correct draw in the picture) and as consequence the moment of rotation 1 (bent arm) is less compared to the moment of rotation 2 (SA). If we need to resist to the moment of rotation we need to generate a different effort. 

Normally what's happen is that D is the same but there are different muscles activation. It is not a case that people with the full planche cannot hold a bent arm planche and vice versa. I prefer to say that you can become stronger in what are you training for. I explain here my hypothesis:

-during the bent arm version the chest is a lot more involved, it is stretched something closer to the best length to generate effort (and this is normal) but you should be trained for this position (you can easily understand the level of stretch by analyzing the upper arm position)

-during the bent arm position biceps is involved a lot in order to avoid full elbows extension

If you have never trained chest specifically you cannot counter balance the leverage of the body, same thing could be said for the biceps. You can easilty see that a people who normally train the hollowback press and the full planche probably has the necessary strength for both type of positions. So it is not correct define that SA is harder always. I'm a monster on full bent arm planche but weak on SA version. But if you have never trained for bent arm work I understand you..if you cannot hold the BA version. 

Then your equations are insufficiently detailed for this particular problem.

About 30sec of work will easily confirm that the SA planche is several orders of magnitude more difficult than the BA planche.  

Please post the video of your attempting to prove otherwise.

Yours in Fitness,

Coach Sommer

2 hours ago, Coach Sommer said:

Then your equations are insufficiently detailed for this particular problem.

About 30sec of work will easily confirm that the SA planche is several orders of magnitude more difficult than the BA planche.  

Please post the video of your attempting to prove otherwise.

Yours in Fitness,

Coach Sommer

Thanks for chiming in Coach! However, my question is not "Which one is harder?", that's rather obvious hehe. My question is "Why is the SA harder than BA?". 

3 hours ago, Eva Pelegrin said:

Physics alone won't give you the answer. As Alessandro pointed out, you have to understand something about functional anatomy, how the body works as a whole, in motion or stillness.

Thanks for chiming in Eva! I guess you're saying this is simply too complex to even come up with an answer? It's a shame because usually it's easy to tell why an exercise is harder than another :/

3 hours ago, Alessandro Mainente said:

You equations it is correct, I was confused since in some pl push up executions I noticed that at the end of a planche push up, D it is not the same . but I admitt that those cases are typical of the last planche push up where people tend to become fatigued. normally D is the same.

Yes, D is simply the distance between the COM and the shoulders. If you aren't piking, this should be roughly the same.

3 hours ago, Alessandro Mainente said:

1-the bent arm variation has its moment of rotation (i think you mean torque)  that could be expressed as M1 = Force₁ * the arm of force₁

2-the SA variation has its own MoR that could be expresses as M2 = Force₂ * the arm of force₂

In both cases the Force that you should "defeat" is the same bodyweigth .

We can now compare the 2 equations and you can see that in the first case the arm of the force is less compared to the SA variation (you made the correct draw in the picture) and as consequence the moment of rotation 1 (bent arm) is less compared to the moment of rotation 2 (SA). If we need to resist to the moment of rotation we need to generate a different effort. 

 

I'm not sure what "Moment of Rotation" is. Never heard that term before. From your equations, it looks like you're talking about Torque, so that's what I'll call it here.

The torque is NOT just (Force1)*(arm of the force) as you think. Torque is the (arm of the force)*(the perpendicular component of the force). Or, for easy computation, simply T = F*L*sin(theta) where F is Force, L is length of the arm, and theta is the angle between them.

So in a plank push-up, the angle between force and arm is zero. Sin(0) = 0, so torque is zero. In an Iron Cross, the angle between force and arm is 90 degrees, so the Torque can be simplified to your equation of T = F*L.

In the SA, the lever arm is longer BUT theta has become smaller. And they change in a way that they cancel out, if you follow my math. 

3 hours ago, Alessandro Mainente said:

-during the bent arm version the chest is a lot more involved, it is stretched something closer to the best length to generate effort (and this is normal) but you should be trained for this position (you can easily understand the level of stretch by analyzing the upper arm position)

-during the bent arm position biceps is involved a lot in order to avoid full elbows extension

This is very interesting Alessandro, and I think this would have to be it. It looks like the shoulders are nicely stretched out, which helps support the position. The biceps also seem like they have a more advantageous line of pull.

Does this mean that the BA planche is a better element for training bicep and chest strength?

3 hours ago, Alessandro Mainente said:

So it is not correct define that SA is harder always. I'm a monster on full bent arm planche but weak on SA version. But if you have never trained for bent arm work I understand you..if you cannot hold the BA version. 

This is very interesting Alessandro. Thank you for your help!

I made a simple way to explain it, there are some language barrier when people learn with different languages and different terms! It's fine..

btw talking about external forces the ba and sa are equals.that's the fact.

the problem should be analyzed inside. I will try to be as clear as possible: If you can hold the SA planche 1 sec and the bent arm planche 10 seconds then you SA is closer to maximal effort while the ba is moving away from maximal strength. During the bent arm version changes the extra muscular coordination (the way in which muscles work together), from the SA where there Is a sort of isolation of the anterior shoulder to the BA where ant shoulder works together with other muscle. Appears pretty natural that the total amount of muscles involved on the BA is higher and since the torque on shoulder is the same, something changed outside the shoulder. With high probability we could see that the intra muscular coordination of ant deltoid for SA and BA is the same, but the extra muscular coordination between ant delt and the other muscles is definitely different and higher in bent arm planche.

until the external forces are held at the same, if you can show more extra muscular coordination then the position is easier to hold.

i apologize for the short written but it is a lot more complicated! I hope you've understood.

You can use a lot more muscle mass in the Bent Arm Planche, namely the chest and triceps. It also involves less connective tissue strength (remember that your instincts will try to protect your elbows).

About leverage and physics, I'm not sure you can really just model your arms as sticks. Your body has a bunch of sticks (your bones), which are connected by joints, which your muscles pull at specific insertion points by contracting and lengthening. Probably key to this is how in the BA planche your actually have two levers, one going from your wrists to your elbow and from your elbow to your shoulders, whereas in the SA Planche just one longer lever going from your shoulders. However these levers aren't like levers you would have in a stick figure, remember that you have muscles and specific insertion points where muscles pull on these levers.

8 hours ago, Alessandro Mainente said:

I made a simple way to explain it, there are some language barrier when people learn with different languages and different terms! It's fine..

btw talking about external forces the ba and sa are equals.that's the fact.

the problem should be analyzed inside. I will try to be as clear as possible: If you can hold the SA planche 1 sec and the bent arm planche 10 seconds then you SA is closer to maximal effort while the ba is moving away from maximal strength. During the bent arm version changes the extra muscular coordination (the way in which muscles work together), from the SA where there Is a sort of isolation of the anterior shoulder to the BA where ant shoulder works together with other muscle. Appears pretty natural that the total amount of muscles involved on the BA is higher and since the torque on shoulder is the same, something changed outside the shoulder. With high probability we could see that the intra muscular coordination of ant deltoid for SA and BA is the same, but the extra muscular coordination between ant delt and the other muscles is definitely different and higher in bent arm planche.

until the external forces are held at the same, if you can show more extra muscular coordination then the position is easier to hold.

i apologize for the short written but it is a lot more complicated! I hope you've understood.

I am in complete agreement with you here and I also think this is most likely the reason why it can be much easier. Thank you for your time! 

6 hours ago, Christian Nogueira said:

You can use a lot more muscle mass in the Bent Arm Planche, namely the chest and triceps. It also involves less connective tissue strength (remember that your instincts will try to protect your elbows).

About leverage and physics, I'm not sure you can really just model your arms as sticks. Your body has a bunch of sticks (your bones), which are connected by joints, which your muscles pull at specific insertion points by contracting and lengthening. Probably key to this is how in the BA planche your actually have two levers, one going from your wrists to your elbow and from your elbow to your shoulders, whereas in the SA Planche just one longer lever going from your shoulders. However these levers aren't like levers you would have in a stick figure, remember that you have muscles and specific insertion points where muscles pull on these levers.

Thanks for chiming in!

As far as modeling goes, I don't really see how "different insertion points" have anything to do with the question. The insertion point (and distance) for, say the biceps, remains the exact same between both exercises so the length of that arm is constant. My drawing just simply show that the other lever (from force to joint) also remains constant so overall torque must be very similar. Perhaps I'm misunderstanding what you mean by insertion points? Sorry :/

The simple thing I'm trying to show is that people assuming there is more torque because a straighter arm is a longer arm... but they don't realize that the angle of the BA is 90 degrees (maximum torque!) While that of the planche is much less. So they end up canceling out.

Please tell me what kind of lever it would look more like, because of insertion points? Just one example, like for the elbow just to get a feel for it. Thanks!

Incorrect.  Insertion points are extremely important as they are the weak links in the chain of support.

Yours in Fitness,

Coach Sommer

Planche is all about how much you can lean your upper body in front of you hands wether it's a Bent arm or straight arm. Bent arm is easier as you have more body parts involved than straight arm. think of the Planche as an old fashion scale. It's even called a Scale in the gymnastics code of points. Your hands are going to be the middle part of the scale (center of mass) you want to evenly distribute your weight on both sides of center of mass. Obviously that's going to be easier with bent arms than straight. Wether you want a BA or a SA planche practice a lot of lean.

4 hours ago, Jesus Candal said:

Thanks for chiming in!

As far as modeling goes, I don't really see how "different insertion points" have anything to do with the question. The insertion point (and distance) for, say the biceps, remains the exact same between both exercises so the length of that arm is constant. My drawing just simply show that the other lever (from force to joint) also remains constant so overall torque must be very similar. Perhaps I'm misunderstanding what you mean by insertion points? Sorry :/

 

The simple thing I'm trying to show is that people assuming there is more torque because a straighter arm is a longer arm... but they don't realize that the angle of the BA is 90 degrees (maximum torque!) While that of the planche is much less. So they end up canceling out.

Please tell me what kind of lever it would look more like, because of insertion points? Just one example, like for the elbow just to get a feel for it. Thanks!

I think it matters because, think for example of just the triceps. In a SA Planche, since your arms are locked your triceps muscle can't really contract more, it's not contributing to movement much more. 

However in a BA Planche, when you are hovering over the balance point, your triceps are not fully contracted and they are contracting strongly in order to extend the arm to counteract what gravity is doing, i.e., pulling your body down. So we can agree that one difference is that tricep contribute to the movement, whereas in the SA planche not really. 

Now think that the triceps attaches to the scapulae, to the humerus and elbow (hence the name, triceps). A muscle works by shortening, which pulls at the the insertions and makes your bones move. So in this case the motion of extending the arms is actually having pulling force at the elbow joint and the shoulder joint. The fact that you have more muscle mass in the movement, doesn't just say that you can exert extra force because of more motor units, but it also means that this force is applied in different points of your "sticks". So it's kind of like putting one end of a rod on a table and grabbing the other end of the rod with both hands and pressing, versus grabbing it with one hand on one end and one hand near the middle, for this case.

I think the same analysis applies to the chest muscle which work a lot more in the BA Planche (and now that I am on the BA planche progression in F2, I feel like it's traditional BodyBuilding "chest day").

Caveat lector, I have no actual training in anatomy and physics is a distant memory from my college years so I may be completely wrong here :). This is just my reasoning regarding this problem.

Umh, I don't know. I don't buy this whole insertion point theory. The insertion point is the same between both variations. Unless the insertion point somehow changes when you bend your arms, I don't see how this would favor either variation. 

Alessandro, you seem to be familiar with the physics behind the movement. Here's an idea that my friend and I just came up with. During BA Planche, the entire weight of the body is used to torque the shoulder. During the SA PL, a fraction of this weight (M*g*sin(theta) to be exact) is used to torque the shoulder, but due to the longer arm, it turns out to cancel out to be the same torque as in BA. Good so far, we agree here.

However, the other fraction (the one parallel to the arms... M*g*cos(theta)) provides a compression force along the arm which is similar to a support position (think top of a push-up) which must be opposed by the triceps and shoulders. I've attached some simple work, to show you this additional component that, unlike torque, DOES depend on arm length (...interesting). If you had super short arms (as short as D), then this force would be zero... Which makes sense because it'd be like doing a maltese, with arms by your sides. But if you have normal sized arms, then this force is nonzero and actually quite relevant as it would be in the order of Bw*0.7. That's around the same amount as holding the top of a push-up.

So it's like the Planche has a torque component of the BA Planche, AND a support component of the top of a plank, at the same time. This would be a pretty dramatic increase in force asked to the joints, so perhaps this is why it is much harder. This is why doing a Tuck Planche not only feels like you're trying to raise your hands overhead, but also like you want to straighten them under this compressive force.

For one, I imagine the ability of two levers (the arm) to act as one, without hinging (at the elbow), depends on the force acting to prevent that hinge from collapsing. So in that sense the SA is harder because you're acting against the elbow wanting to hinge, whereas in the BA you're acting with it. But I could be pulling this out of my ass because the one thing I am certain of is that I am not a trained engineer.

25 minutes ago, Christian Nogueira said:

I think it matters because, think for example of just the triceps. In a SA Planche, since your arms are locked your triceps muscle can't really contract more, it's not contributing to movement much more. 

However in a BA Planche, when you are hovering over the balance point, your triceps are not fully contracted and they are contracting strongly in order to extend the arm to counteract what gravity is doing, i.e., pulling your body down. So we can agree that one difference is that tricep contribute to the movement, whereas in the SA planche not really. 

 

I don't agree with this. Actually, I'd argue the opposite. The triceps are working very hard during a SA planche. The elbows want to bend because of the component of weight parallel to your arms I explain on my post before. Just because the elbows are straight doesn't mean the triceps aren't hard at work (think top of a dip or a push-up). As long as you have some kind of force trying to get your hand to your shoulder, the triceps will have to fight it.

On the other hand, during the BA PL, all force is torque. There is no force along the arm, so actually the triceps would do very little work. There is no force trying to close the angle of the elbow. In fact the force is all trying to OPEN the angle of the elbow, which is why the biceps are hard at work during the BA Pl.

However, your explanation about the rest of the attachments makes sense to me. Perhaps the way the chest is attached means that it can get more leverage when the arms are alongside of it. I appreciate your response!

You are looking at this far too simply. You need to know the antomy, biomechanics, neurobiology and neuroanatomy to answer this question. You need to measure what happens at the fingers, wrist, elbow, shoulder, cervical, thoracic and lumbar spine, pelvis, hips, knees and foot. You need to measure what happens to the bones and then the biomechanics of how each joint moves. This will vary from person to person as we are all different. 

Or you could just do the exercises, ask those that coach and are experienced in these exercises and accept that one is harder than the other.

2 hours ago, Jesus Candal said:

I don't agree with this. Actually, I'd argue the opposite. The triceps are working very hard during a SA planche. The elbows want to bend because of the component of weight parallel to your arms I explain on my post before. Just because the elbows are straight doesn't mean the triceps aren't hard at work (think top of a dip or a push-up). As long as you have some kind of force trying to get your hand to your shoulder, the triceps will have to fight it.

On the other hand, during the BA PL, all force is torque. There is no force along the arm, so actually the triceps would do very little work. There is no force trying to close the angle of the elbow. In fact the force is all trying to OPEN the angle of the elbow, which is why the biceps are hard at work during the BA Pl.

 

However, your explanation about the rest of the attachments makes sense to me. Perhaps the way the chest is attached means that it can get more leverage when the arms are alongside of it. I appreciate your response!

I disagree on this. I can't speak on how a SA planche works your triceps, because I don't have a straddle planche. But I do have a bent arm straddle planche and it works the triceps like mad, much more than tuck planche which would be like my 1rep max in straight arm work. This is all very subjective, but to me straight arm work feels very different in terms of what get tired and sore when compared to bent arm work.

I also disagree that when you get into the lean with straight arms as in a planche or even a simple planche lean, I don't gravity acts to bend your arms. You lock your arms and that's it, your biceps is working hard to make sure your aren't wrenching your elbow to where it's not supposed to go, but I've never ever failed when I'm tired due to unlocking of the arms. Protraction and depression will fail first, heck for me posterior pelvic tilt will fail before my arms ever unlock. Searching this forum, I've found this https://www.gymnasticbodies.com/forum/topic/11094-planche-and-muscle-involved/ topic, where the consensus seems to be, as your arms get straighter more tension goes from your triceps to your biceps and vice versa. My guess is that it relates to the relative position of the elbow and shoulder, as the elbow goes above the shoulder in BA planche or as the shoulder goes above the elbow. 

But I think you can experimentally verify this. Do a planche lean and then do a lean in the bottom position of a planche pushup. Personally I feel the triceps much more in the bottom, which is like a bent arm planche lean analogue to the straight arm planche lean.

I think that the total amount of force is the same in either position, but the problem is that force that each individual muscle has to produce varies as their attachment points move through space and if they can't contract any further because the joint the muscles move have reached the limit of their range of motion. It just so happens that the straight arm planche is where the muscles doing the work are smaller and the attachments in the bones they are pulling aren't in the best leverage to mantain the planche position.

Whatever the model, to be useful for anything it has to agree with what everyone can verify with some sweat and work :D.

Gotcha. Well it looks like maybe the topic and ultimately the answer is much more complex and not easy to find. I guess at the very least we can all agree it isn't due to an increase in torque or decrease in shoulder leverage unlike the tuck/straddle/full variations, where it is exactly that. It seems like Alessandro thought this at the beginning, but now has thought of a couple more interesting points which I really think might be right on point!

If you have a second Alessandro, I'd love it if you looked through my past post about the force going both parallel and perpendicular to the arm because I believe this might be why it becomes "magnitudes" more difficult. It is actually a situation that happens often in physics (think a box suspended by two strings, angled from vertical... each string will have more tension than half the weight of the box! Because the strings produce horizontal matching components as well).

Anyways, I appreciate all the responses guys. My friend and I feel a bit more enlightened as far as the topic is concerned!