How Michael Jackson's Dancing Defied the Laws of Biomechanics

Phil Walter, Getty Images
Phil Walter, Getty Images

From the time he debuted the moonwalk on broadcast television in 1983, Michael Jackson transcended the label of "dancer." His moves seemed to defy gravity as well as the normal limits of human flexibility and endurance.

Now we have some scientific evidence for that. Three neurosurgeons from the Postgraduate Institute of Medical Education and Research in Chandigarh, India, recently published a short paper in the Journal of Neurosurgery: Spine that examines just how remarkable one of Jackson's signature moves really was.

In the 1988 video for "Smooth Criminal" and subsequent live performances, Jackson is seen taking a break from his constant motion to stand in place and lean 45 degrees forward. Both he and his dancers keep their backs straight. Biomechanically, it's not really possible for a human to do. And even though he had a little help, the neurosurgeons found it to be a pretty impressive feat.

An illustration of Michael Jackson's 'Smooth Criminal' dance move.
Courtesy of 'Journal of Neurosurgery: Spine.' Copyright Manjul Tripathi, MCh.

Study co-author Manjul Tripathi told CNN that humans can't lean forward much more than 25 or 30 degrees before they risk landing on their faces. (He knows, because he tried it.) Normally, bending involves using the hip as a fulcrum, and erector spinae muscles to support our trunk. When Jackson leaned over, he transferred the fulcrum to the ankle, with the calf and Achilles tendon under strain. Since that part of the body is not equipped to support leaning that far forward without bending, the "Smooth Criminal" move was really a biomechanical illusion. The act was made possible by Jackson's patented shoe, which had a "catch" built under the heel that allowed him to grasp a protruding support on the stage. Secured to the floor, he was able to achieve a 45-degree lean without falling over.

But the neurosurgeons are quick to point out that the shoes are only part of the equation. To achieve the full 45-degree lean, Jackson would have had to have significant core strength as well as a strong Achilles tendon. An average person equipped with the shoe would be unable to do the move.

How does this apply to spinal biomechanics research? The authors point out that many dancers inspired by Jackson are continuing to push the limits of what's possible, leading to injury. In one 2010 paper, researchers surveyed 312 hip-hop dancers and found that 232 of them—almost 75 percent of the cohort—reported a total of 738 injuries over a six-month period. That prevalence could mean neurosurgeons are facing increasingly complex or unique spinal issues. The surgeons hope that awareness of potential risks could help mitigate problems down the road.

[h/t CNN]

How Did 6 Feet Become the Standard Grave Depth?

iStock
iStock

It all started with the plague: The origins of “six feet under” come from a 1665 outbreak in England. As the disease swept the country, the mayor of London literally laid down the law about how to deal with the bodies to avoid further infections. Among his specifications—made in “Orders Conceived and Published by the Lord Mayor and Aldermen of the City of London, Concerning the Infection of the Plague”—was that “all the graves shall be at least six feet deep.”

The law eventually fell out of favor both in England and its colonies. Modern American burial laws vary from state to state, though many states simply require a minimum of 18 inches of soil on top of the casket or burial vault (or two feet of soil if the body is not enclosed in anything). Given an 18-inch dirt buffer and the height of the average casket (which appears to be approximately 30 inches), a grave as shallow as four feet would be fine.

A typical modern burial involves a body pumped full of chemical preservatives sealed inside a sturdy metal casket, which is itself sealed inside a steel or cement burial vault. It’s less of a hospitable environment for microbes than the grave used to be. For untypical burials, though—where the body isn’t embalmed, a vault isn’t used, or the casket is wood instead of metal or is foregone entirely—even these less strict burial standards provide a measure of safety and comfort. Without any protection, and subjected to a few years of soil erosion, the bones of the dearly departed could inconveniently and unexpectedly surface or get too close to the living, scaring people and acting as disease vectors. The minimum depth helps keep the dead down where they belong.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

This article originally appeared in 2012.

One Good Reason Not to Hold in a Fart: It Could Leak Out of Your Mouth

iStock/grinvalds
iStock/grinvalds

The next time you hold in a fart for fear of being heard by polite company, just remember this: It could leak out of your mouth instead of your butt. Writing on The Conversation, University of Newcastle nutrition and dietetics professor Clare Collins explains that pent-up gas can pass through your gut wall and get reabsorbed into your circulation. It's then released when you exhale, whether you like it or not.

“Holding on too long means the build up of intestinal gas will eventually escape via an uncontrollable fart,” Collins writes. In this case, the fart comes out of the wrong end. Talk about potty mouth.

A few brave scientists have investigated the phenomenon of flatulence. In one study, 10 healthy volunteers were fed half a can of baked beans in addition to their regular diets and given a rectal catheter to measure their farts over a 24-hour period. Although it was a small sample, the results were still telling. Men and women let loose the same amount of gas, and the average number of “flatus episodes” (a single fart, or series of farts) during that period was eight. Another study of 10 people found that high-fiber diets led to fewer but bigger farts, and a third study found that gases containing sulphur are the culprit of the world’s stinkiest farts. Two judges were tapped to rate the odor intensity of each toot, and we can only hope that they made it out alive.

Scientific literature also seems to support Collins’s advice to “let it go.” A 2010 paper on “Methane and the gastrointestinal tract” says methane, hydrogen sulfide, and other gases that are produced in the intestinal tract are mostly eliminated from the body via the anus or “expelled from the lungs.” Holding it in can lead to belching, flatulence, bloating, and pain. And in some severe cases, pouches can form along the wall of the colon and get infected, causing diverticulitis.

So go ahead and let it rip, just like nature intended—but maybe try to find an empty room first.

[h/t CBS Philadelphia]

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