Space & Innovation

How Much Force Does It Take To Break A Bone?

It seems like some people break bones all the time, while others consistently end up unscathed. What exactly does it take to break a bone?

It's the kind of question that isn't likely to occur to you unless you're a physician, medical researcher or professional wrestler: How much force does it take to break a bone, anyway? Amy Shira-Teitel, never afraid, investigates in today's DNews report.

If you're in the market for a short answer, it takes about 4,000 newtons of force to break the typical human femur. But in general terms, there is no real answer, as the amount of force required depends on the bone itself, its position in the body, and the angle of attack.

The femur, or thigh bone, is the toughest bone in the body to break. It's the largest and thickest bone, for two things, and it's also protected by all those leg muscles. The collarbone, conversely, is relatively small and close to the surface of the skin, and therefore is one of the most commonly broken bones.

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In addition to the amount of force applied, the angle of blow can make all the difference as to whether a particular bone will break. The dense outer layer of your bones is made from columns of collagen and calcium phosphate, almost link a bundled collection of twigs. These columns run vertically and as such are good at absorbing compressing forces. This is what your leg bones to when you jump.

However, forces coming from the side – or shear forces – are trouble for any kind of lengthy bone. The twig metaphor is again handy, if disturbing: Imagine breaking a bundle of twigs in half.

In addition to all this, bones vary in thickness and toughness from person to person, depending on age, diet and lifestyle. It's true that calcium helps build strong bones. Alas, it's also true that bone density peaks around age 30. It's all downhill from there. Amy has more details in her report, including a bonus dose of information on space science, provided entirely free of charge.

-- Glenn McDonald

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