T Nation

Spine Strength Formula?

I’ve been having a discussion with a few colleagues over a formula we were told in college saying that

“the strength of the spine is proportional to the number of its curvatures, by the formula R = C^2+1 . The human spine has three [sometimes I find “four”] curvatures so its strength is 3^2+1 = 10 times higher than if it didn’t have the curvatures”.

Is this formula valid?
Does anyone know the source?

It’s whether uber-advanced biomechanics, or it’s false, because as an engineer, I can tell that simply adding some curvatures to a bar will not in any way increase its strength.

My colleagues keep telling me “it’s like a spring”, and I’m sure it isn’t… [to which I say, spring my ass. Additional coils make the deformation in each coil smaller, and as such the tension in every bit of material smaller]

If it actually works like a spring, do tell.

Anyway, I’d appreciate it if anyone could explain to me where this formula comes from, or if it makes any sense…

[quote]Sterneneisen wrote:
I’ve been having a discussion with a few colleagues over a formula we were told in college saying that

“the strength of the spine is proportional to the number of its curvatures, by the formula R = C^2+1 . The human spine has three [sometimes I find “four”] curvatures so its strength is 3^2+1 = 10 times higher than if it didn’t have the curvatures”.

Is this formula valid?
Does anyone know the source?

It’s whether uber-advanced biomechanics, or it’s false, because as an engineer, I can tell that simply adding some curvatures to a bar will not in any way increase its strength.

My colleagues keep telling me “it’s like a spring”, and I’m sure it isn’t… [to which I say, spring my ass. Additional coils make the deformation in each coil smaller, and as such the tension in every bit of material smaller]

If it actually works like a spring, do tell.

Anyway, I’d appreciate it if anyone could explain to me where this formula comes from, or if it makes any sense…[/quote]

Well, to me, it seems logical. I don’t have anything to back it up, but it just looks right to me. Not the exact math part, just the thing that the curvatures will add to strength.

Yep. And to me it seems/feels that the spine would buckle easier if there were no curvatures, but engineering tells me a mast doesn’t hold better because it’s made of curved wood.

But the formula seems to make no sense whatsoever.

And I want to learn whether or not it does.

I’m no fancy-pants book lernd guy, but it seems to me that you couldn’t do something like this without taking into account the surrounding musculature and how it effects the spine

Plain as day that without the surrounding musculature, ligaments etc. the curvatures would be useless.

Still doesn’t explain the formula.

Also, let us take note that most every champion deadlifter doesn’t maintain an arch in any part of his spine.

I googled the hell out of this skanka and found that its the formula for the resistance of the spine to compression forces.

See: http://openi.nlm.nih.gov/detailedresult.php?img=1198239_1746-1340-13-16-2&req=4

I couldn’t find a reference in that site, but you might be able to make more sense of the techno-babble gobbledygook than I could.

Big thank you, MartyMonster.
Looking through it.

I’m beginning to think some doc who read about coils or something a few hundred years ago decided to spurt out this gem.

From an engineering standpoint, curvatures will REDUCE the strength of a straight bar, because they will make the bar become subject to bending moment, not only to compression…

[quote]Sterneneisen wrote:
I’m beginning to think some doc who read about coils or something a few hundred years ago decided to spurt out this gem.

From an engineering standpoint, curvatures will REDUCE the strength of a straight bar, because they will make the bar become subject to bending moment, not only to compression…[/quote]

That seems reasonable.

A curved sword is stronger than a straight sword when you slash in the direction of the curve. Hence cavalry sabres are curved. Swords used for stabbing actions are straight.

I’m no fancy-pants book lernd guy, but it seems to me that you couldn’t do something like this without taking into account the surrounding musculature and how it effects the spine

By the way, I’ll presume that the formula refers to strength to static demands, not dynamic/shock.