How Taut Does Your Butt Need to Be to Bounce a Quarter off It?

‘If butt skin were any bouncier, it would be illegal to hit a golf ball with it’ — an assistant professor of physics.

Butt_Quarter

Everyone loves a good butt, and while, in my humble opinion, every butt deserves some respect and appreciation, humanity has, of course, formulated a simple trial to separate the best butts from the butt-pack: the Quarter Test. The test is simple: Bounce a quarter off of a chosen butt, and then measure the resulting rebound. The higher the bounce, as Urban Dictionary explains, the better the butt:

“It is commonly accepted that if a clean bounce launches the quarter about one to two feet into the air, then the test subject has passed. In the fortunate case that the quarter reaches heights above those aforementioned, then the particular pair of buttocks under scrutiny are considered Serious Badonk.”

While the exact inception of the Quarter Test is unclear, it could be a play off of an old military legend, which says that new recruits are forced to make their beds, or “racks,” cleanly and tightly enough for an inspecting sergeant to bounce a quarter on the blanket (although nowadays, it seems that few military personnel actually undergo such tests). Still, you can see how we could have taken this tale as an excuse to toss quarters at butts.

Anyway, the bigger question here is, how taut does a butt actually need to be in order to pass with flying colors? For some help answering that, I reached out to Alex Klotz, an assistant professor in the department of physics and astronomy at California State University, Long Beach, who looked to science to break things down.

“How well something bounces has to do with a material property called the Coefficient of Restitution (or COR),” Klotz explains. “This number represents the fraction of initial velocity that an object retains after bouncing. If the object just flops, that’s a 0. If the object bounces back perfectly, that’s a 1.0. We can get a sense of what the COR has to be for a good bounce based on regulations from various sporting bodies: According to the International Table Tennis Federation, a ping-pong ball has to have a COR of about 0.87. If the COR between a golf club and a golf ball exceeds 0.83, that’s considered an unfair advantage. The allowed pressure in a basketball corresponds roughly to a range of COR between 0.73 and 0.81. These numbers are pretty clustered around 0.8, which seems to be the acceptable level for something to be bouncy.”

As for how that all applies to quarters and butts, Klotz says, “Normally, to find the bounciness of a human butt, I’d start looking up various proxies to connect what we know about butts to a COR — what can the resistance to injuries after falling tell us about the compressibility of human skin and muscle; what’s the relationship between the compressibility of a material and its COR; how does the curvature of the butt surface affect this and so on. However, I don’t need to do that, because a group of researchers straight-up went out and measured the COR of people’s butts.”

Of course they did.

“A group of scientists in Manchester, U.K., led by Dr. Abigail Langton, went out to measure the elastic properties of human skin as part of a way to understand its resilience to injury, and they published their results in the British Journal of Dermatology,” Klotz says. “They were also interested in comparing skin between volunteers of European and African descent, as part of developing ways of diagnosing dermatologically ‘healthy’ skin between patients of diverse backgrounds. They took 30 participants, laid them down, cleaned a patch of butt cheek with an alcohol swab and prodded them with a device called a Ballistometer, which works by forcing a small probe into the skin and measuring how fast it returns to its initial position due to the skin’s internal resistance.”

And? And..?!?!

“They found that the Coefficient of Butt Restitution was 0.82 in both black and white participants,” says Klotz. “This was significantly bouncier than measurements of forearm skin, which we don’t care about right now. Essentially, what this implies is that if butt skin were any bouncier, it would be illegal to hit a golf ball with it.”

In other words, your butt is naturally pretty darn bouncy and should have no problem launching a quarter into orbit.

But then, why might some butts do better on the Quarter Test than others? “Because the measurements were based on the properties of the skin — and not the underlying fat or muscle — I suspect that it’s not so much of a fitness thing that affects butt bounciness, but rather age and overall skin health,” Klotz explains. So, really, to effectively bounce a quarter off of your butt, the best thing you can do is regularly slap moisturizer on that thang. However, if fitness plays even the slightest part, here are some tips on firming up dat butt from decorated personal trainer Jonathan Jordan, who says, “Booty is my specialty.”

“The most important thing to do before any booty workout is to activate the glute muscles,” Jordan explains. “They tend to fall asleep easily, especially if you have a desk job where you sit all day. So before you lift any weights, activate them by doing some band work: I love this band and recommend 60 seconds of side steps and 60 seconds of glute bridges one or two times.”

From there, he suggests focusing on the following exercises, which bulk up your hips, many of which are explained in greater detail here:

  • Kettlebell swings
  • Hip thrusts
  • Every kind of squat, including goblet, back and front squats
  • Deadlifts and RDLs, or hip hinges

Then, he suggests following those up with these single-leg workouts:

Great!

Now, uh, anyone got a quarter?