/sci/ - Science & Math

>>10471394
dam son, you ride motorcycles? fuck fat girls? How that shit happen?

bump

>>10471398
I was arm wrestling with a friend and we were at stalemate for like 2 minutes straight, torqued my shoulder like a retard and it just snapped. I lift weights but I'm not some body builder. I thought I had weak bones or something but they're completely healthy and normal, just bad physics.

Please respond

>>10471394

you can easily estimate it. the pressure a bone can take is roughly 15 kg per mm^2 , pulling force it can take is 10 kg per mm^2, however a torque (which implies a "bending moment") is much harsher on the bone, and the only structures to prevent/lessen a bone from bending/torquing (and breaking) are muscles


so you could calculate an upper bound (with 10 kg per mm^2) and a lower bound with the force it takes to tear a muscle (or rather the tendons) is 6 kg per mm^2

the lower bound is much less than that because these numbers for the tendons are for directions the tendon fibrils are aligned to so its going to tear much earlier than at 6 kg per mm^2 if you apply a torque from the side

>>10471414
Can you explain it to me as if I'm a brainlet which I am? I had no muscle/tendon damage if that helps. I'm sorry I'm a retard.

>>10471424

bones themselves are pressure resistant (from the minerals) and pull resistant (from collagen type 1) but not bend resistant, so any kind of torque will really fuck up a bone

the components that relieve/lessen torques are muscles and tendons , which is why you should train your glutes for example or your posterior chain

>>10471431
So basically what you're saying is that you can snap a bone quite easily when it comes to torque? I guess I wanted to know if you had to be "strong" to do that to yourself to cope with snapping my arm like a retard but it makes sense from what you're saying that it's simple physics and a relatively weak person could manage the same injury.

Welcome to the club anon. Whilst I broke mine in a much more exciting way, the doctors all assumed it had been a motorbike accident. Apparently that’s pretty much the only (typical) way to break the humerus like that; i.e. you need some serious force for it to give out.

When did this happen? You getting it pinned back together?

a large amount of torque is entirely achievable purely due to biomechanics, if you and your friend lock/torque your joints and body correctly

>>10471437

you probably dont need to be very strong , as for a torque oyu can just increase the length of the torque moment to make it much larger

>>10471414
The strength of his bone really depends on the mineral density and probably the cross sectional area, even if he could estimate the force vector to determine how much was a sheering force, there's probably not an easy way to realistically determine how much force would be required to break his arm from that position, it would be eaiser to just have his friend estimate how much force he produced by replicating the scenario, measuring, and assuming the breaking point was somewhere close. Otherwise as a gross measure just find the tensile strength of bone at your mineral density when opposing a sheering force

>>10471445

???? what do you think the numbers i wrote mean? 10 kg mm^2 and 15 kg mm^2 for the pressure

bone itself is not built to manage bending/torque moments and has no way of compensating for them

>>10471445

mineral density has almost nothing to do with how much torque is needed to break a bone , since bones dont grow to reduce torques , they grow to reduce pressure/pulling forces

>>10471439
It happened about 6 weeks ago and I'm just wearing a brace, able to bend my elbow, move around, no radial nerve damage whatsoever as well which I'm thankful for. Checked in with the doctor last week and its started knitting thankfully, surgery is off the table and I'm healing quicker than usual apparently. The fucking pain was unbelievable in the ER though, like mind blowing. Prior to that I could only imagine what that type of pain would feel like but feeling it was an experience to say the least and put my sense of pain in an entirely different realm.
>>10471440
>>10471441
>>10471445
>>10471449
Thanks for the replies, how would you convert those numbers
>10 kg mm^2 and 15 kg mm^2
To kg per cm? Can you even do that? Again apologize if I look like a brainlet but I'm honest and completely willing to admit I am when it comes to mathematics.

>>10471451
This isn't true, low BMD is absolutely correlated with lower resistance to sheering forces

>>10471453

its 100-150 kg per cm^2 but thats for pressure and pulling force , not a torque moment

>>10471465
Ah I see, so is there anyway to account for torque energy required to cause a fracture like that or are there too many variables?

>>10471457

low BMD is caused mainly by the hormon sclerostin , which is secreted more by osteocytes when there has not been any pressure/pulling forces on the bone itself

so you are mistaking consequence and origin, people don't train (and their MUSCLE mass reduces because they dont train as well) -> their BMD gets lower and because they have lower amount of muscle mass they can not compensate for torques

the BMD itself has almost nothing to do with the bones ability to deal with torques

>>10471467

honestly i dont know , torque itself is a vector (with the same unit as energy, which is a scalar) and you can easily make it larger/much smaller by just changing the position of your arm/body

you could probably use the number 600 N per cm^2 which givse the tearing force required to tear a tendon but its probably even less than that

the reason why you dont braek bones all the time from torques is mainly due to your muscles and fat/fascia

>>10471480
Fair enough, thanks for the replies again. Does the 42 N.m thats required in the medical article on it make sense?

>>10471471
>the BMD itself has almost nothing to do with the bones ability to deal with torques
Point me to sources so I can read into this please

>>10471482


hard to say, 42 nm can mean a lot , for the sake of example lets say the humeral bone is 35 cm long , then a torque in the middle of it (required to break it according to the article) would be beating the tip of it with 240 N (""24 kg"" )

>>10471483
>>

its going to be in any anatomy book or histology i dont really remember
just look up sclerostin and you'll understand what im talking about

>>10471498
I'm asking for sources that BMD has nothing to do with resistance to sheering forces because I'm trying to look it up and I'm seeing positive correlations, if I had the text book I'd check but I don't

>>10471506

yes, you'll see positive correlations because people that have lower BMD s will also have less muscle mass

the true connection is between low muscle mass , sclerostin and low BMD and nothing else

>>10471509
Yes that's what I'd like a source force, teasing out that BMD is not a factor in sheering force

>>10471513
>source force
for

>>10471513
>>10471517

shear forces are not what causes a bone to break , im writing about torques here

Same thing happened to me OP. Except it was a bouncer outside a group of bars. He got off scott-free in terms of an assault charge.

>>10471509
I have small bones, is that why I can't build muscle? Wrist is 6.25"

>>10471526
I'm aware bones are resistant to compression and tension but I was taught in biomechanics that sheering forces are what typically breaks bone, and I'm looking for sources that BMD has nothing to do with this

>>10471404
So you can build muscle? I don't know why I can't
At least my arm never breaks since I lose fairly quickly usually

>>10471531
And this is the result post-op.

>>10471531
The Nuremburg defense works great for everyone but Nazis, more a case of being on the winning team. I avoid interactions with people paid to be tough guys because at best they ignore you, at worst you die, you landed somewhere between. But the burden of proof is on you since they're getting paid to be a bully

>>10471541

shearing forces are a combination of pressure and pulling forces
torques dont have anything to do with either of these

BMD does have to do with it, obviously, but it is not relevant because the body compensates for torques (not shearing forces) by activating muscles (in german this is called "Zuggurtungsprinzip")

its similar to how a crane works , as you can see in this pic >>10471555

the plate is fixed such that it prevents/relieves/absorbs torque moments

>>10471531
Fuck thats nasty, really glad I didn't need surgery. How bad was the pain for you?
>>10471542
Yeah I put on muscle extremely easily, I'm naturally muscular, unfortunately that means its easier for me to put on fat too but as long as I eat sensibly I don't and I can cut still.

>>10471578
At time of fracture, moderate.

Now, in general, it does not cause pain but my arm does fail to relax occasionally which causes me moderate distress.

>>10471577
I'm failing to understand how that makes the physical composition of the bone irrelevant, especially in a scenario where the strength of the muscle is obviously against than the force it is resisting. It seems from a vector standpoint that a rotational force can be a sheering force at a set point in rotation, and the muscle would be action against it causing a break (especially with lesser BMD). I understand that bones are resistant to compression and tension because that is how they typically experience force

>>10471596

its not that BMD is irrelevant, if you have a higher BMD you ll also be able to absorb more torque, but not that much more

but the amount of torque a bone can absorb is already very low , already a bone like the femur will bend from the torque cause dby the weight of a normal persons own body

its because of the m iliotibialis that it doesn't actually bend through

>>10471591
Guess I'm just a pussy cause when I was in the ER it was the worst pain I've ever felt.

>>10471601
Thanks, I think my confusion was in the statement that BMD has almost nothing to do with resisting torque because I could agree that bones are inherently not resistive to torque, I just could not write off the correlation of BMD to torque injuries purely based on muscle activity since there's research regarding more obvious sheering injuries suggesting BMD is a factor, and a torque does apply a sheering force hence the physical appearance of the break. I appreciate your explanations.

>>10471531
fug, what'd you do to get xis attention?

>>10471394
Not a doctor here but I have played one on TV also disclaimer.


That is not a mid-shaft to spiral verterbrate incision. That is a bone breaking. There is no humerus spiral fracture. You are broken in the arm. You moved a sofa, it fell on you, it feel you break then, and then you move away from the sofa and it hurt you body.

What you wanted to ask was can we move away from the topic of the break, I want to make the body work for me. Okay. The essence of this is that only when you are able to move the broken bone can you actually move it. It's broken. That's impossible. And the only way to get information out of that broken bone is to splice the membrane from OVER the injury not in it. You are trying to create the conditions for Leukemia. Help yourself unnerve someone that is being arrested for making this kind of trouble. Not someone being watched to get him to do so as like a pundit surprise attack or surprise buttsex. Which is always nice.

Okay so with the injury in tow then, the negligent party has a lot to offer the medical fields of science. Perhaps you might want to wander off to the hospital instead of hold an x ray up to take pictures. I believe you can be sent to insane assylum for such things if you are really being so clever as to disguise yourself as some anonymouse entity. Like, you'll just join leukemia anonymous kind of thing. Don't undermind that they don't like giving away free work and when it's given to them they will pay you back in full because that's life. And we generate for it.

>>10471414
I would raise that torque also handles that gesture of "touching" the bone so that when you release the pressure you actually kind of light up the rest of the body and all weight is excluded. You end up nerving up to certain pressure scales but you cannot actually accentuate that to people because of war time problems from a ww2 debacle that we have not concluded is simply the framing for neurodegenerative diseases that were going to pbe put into play by the nazi regime into the continuation of the war AWAY from nazi germany and into China or perhaps Japan. Perhaps the war was ended to purport such things but its more likely someone helped in at the end and the Germans needed away to retaliate at the last moment. Maybe we need to stop reactionary work and pay for some slices of the pie because I still don't eat well and I still hear burning flesh. I used to smoke. It isn't nice to do that.

>>10471653
Finally, an answer that makes sense

>>10471555
You had a boating accident. The water was flooding the pulp on the bone to include that plasma may included in the next charge as you may have been pushing a boat upstead out of the light so that the myelin sheeting didn't arrange the pulse in your heart to organize a fruitful agenda to your eyes. So you didn't bother watching your step and you fell forward, the boat fell back and you got caught fucking your neighbor in the ass by your wife who knows you are not who I am going to say you are. But he did offer his help didn't he? Thank you. America wins again!

fuck you nigger shut up

>>10471655
^__________________^?

>>10471394
eurgh, i can see exactly what happened to your arm there. A pair of footballers did this break to one of them on live TV a few years ago in Australia.

https://www.youtube.com/watch?v=eeSBWpyIib4

>>10471661
That's not my arm but it looks very similar.

>>10471661
As usual, whitey gets rekt.
Is my being white the reason I'm so weak?
Also how do I get those arms

>>10471669
kys faggot :)

>>10471685
Are you another weak cracker?

>>10471689
im a 30ft tall black bvll giant (from the skyrim series)

>>10471652
what

>biking home the other evening in dark and rain
>car pulls out in front of me
>slam into the side of car
>shoulder gets a blue mark and sore
>little finger swells and hurts
At least now I can move and use it. I would be able to tell if it was broken, right?