Short Course in Anthropometry

NPR just ran an extremely detailed article on the importance and study of anthropometry. The topic is the undue stress nursing places on the spine, even when “proper” lifting procedures are followed. Highlighed is the work of Bill Marras (recent Editor of the journal Human Factors), who developed a sensor rig for the forces experienced by the spine. Read for yourself, but if you want the high points:

“Moving and lifting patients manually is dangerous even for veteran nursing staff, Marras says, for several reasons:

  • The laws of physics dictate that it’s easiest to lift something when it’s close to your body. But nursing employees have to stand at the side of the bed, relatively far from the patient.

  • Nursing employees also often bend over the patient. That’s important, because there’s a chain of bones along the spine, called facet joints, hidden under the little bumps protruding under the skin. Those bones interconnect and help absorb loads when standing straight. Marras says that when nurses lift as they’re bending, those bones disengage and their disks take most of the force. Those forces are “much, much higher than what you’d expect in an assembly line worker,” he says.

  • When nurses keep working under these loads, it causes microscopic tears in the “end plates,” which are films as thin as credit cards above and below each disc. Those tears lead to scar tissue, which can block the flow of nutrients into the disks — until, eventually, the disks start to collapse. “You could be doing this damage [to your back] for weeks or months or years, and never realize it,” says Marras. “The event that caused you to feel the problem is just the straw that broke the camel’s back.”

The final conclusion was that people cannot lift other people safely. Assistive machines are needed, and as the article points out, hospitals do not have them.