HOW TO BUILD THE PERFECT BUTT?

1/ Defy gravity

Here's how to make sure the strongest muscle in your body isn't also the laziest.

The science behind your butt

I'm alone with a handsome young doctor who has his hands down my shorts, but neither of us is very happy about it. Joseph, a personal trainer at a luxury gym in Paris, frowns as he struggles to untangle a 19-inch wire attached to an electrode he's stuck to my buttocks.

The electrode is covered with a conductive gel, and he holds it in place while he attaches the other end of the wire to the electromyography (EMS) machine, a bulky piece of equipment that measures electrical activity in your muscles.

2/ Coach Jo, agreed to help me understand what is happening

If necessary, with my glutes when I'm not working them explicitly.

Which is almost never the case.

And it shows. Or rather, it doesn't show on my flat, ordinary butt.

At Coach Joseph's signal , I mimic myriad everyday movements, including walking, jogging at bus speed, lunging at toddler speed, and shifting my weight from hip to hip, as I do while waiting in line at the ATM.

With each movement, the line on the machine's screen does a pathetic little jump; the display looks like a lie detector test without the lies. Coach Jo shrugs and says that's normal, no matter what shape your butt is. "Your glutes don't usually get much use throughout the day," he explains. "The quads do most of the work."

Then I step onto a step and the screen display shows a violent spike. Finally, my gluteus maximus does what it was born to do—or rather, evolved to do: keep me upright as I walk, especially on those more difficult-to-balance stair climbs.

Among the things that set us apart from our limp-jointed primate ancestors are not only our big brains, but also our big butts—or, as Sofia K. puts it, our hyper-trained, well-developed glutes. “This ability to be bipedal is a huge deal,” says coach Arnaud.

3/ It is this muscle which makes it a major component

It is ironic, then, that the largest muscle in our body, which gave man his characteristic upright posture, spends most of the day metaphorically sitting on its butt.

All that is normal for the buttocks

While we obsess over shaping the ideal butt, the multibillion-dollar denim industry and even the government are hoping to define exactly what a typical butt looks like. For years, the rule of thumb for hips was that hips needed to be at least 18 inches wide to fit 95 percent of women's butts, since our hips are wider than men's—or about an inch wider than this magazine when it's open. (Go ahead, sit on it to see how you measure up.) Data has confirmed that our collective posteriors do indeed get wider over time.

4/ When 3D scanning technology was developed, the Air Force

A group of automotive engineers and clothing companies were the first to use it, conducting the Civilian American and European Surface Anthropometry Resource ( CAESAR) study , published in 2002. With CAESAR, "you can get a digital replica of an entire butt in 3-D."

“You can prepare a before and after scan, and see how the garment affects the shape.”

The military has used this data to reconfigure women's uniforms, adding "feminine" cuts - meaning a wider area at the hips and buttocks - to cover more of its female soldiers without having to resort to costly alterations.

The apparel industry then partnered with the U.S. Department of Commerce to conduct the Size USA study, using a different 3D scan with a much larger sample size of 10,000 people including a wider range of body mass indices, ages and ethnicities.

These studies have taught us a lot about the average American woman's buttocks - mainly that they don't exist.

The Size USA study found that 86% of women ages 26 to 55, between 5'3" and 6'1" tall and weighing less than 150 pounds, have a seat circumference of 83 to 110 inches at the widest point.

These figures should be taken with a grain of salt, however, says Romain. "As soon as we start trying to lump together an 'average' female body, we lose touch with reality," she explains.

In other words, you may have a statistically average butt size, but it's unlikely that your weight, height, or waist size will also be average.

A short woman with an average butt size will have a proportionally large butt, while a tall, heavy woman with an average butt size will have a proportionally small butt.

In other words, looking for your dream butt in celebrity magazines is a bad idea.

5/ Discover the muscles of your buttocks

Get your glutes defined with this targeted fitness session

The three main muscles that make up your glutes vision.

1. The small buttocks

The smallest of the gluteal muscles lies directly below the gluteus medius.

2. The gluteus medius

This pork chop-shaped muscle sits near the outside of your pelvis.

3. Gluteus maximus

True to its name, the gluteus maximus is the largest muscle in your body.

A few weeks after my experience with Coach Joseph, I find myself in the gross anatomy lab not far from my gym. On a blindingly white table lie pieces of lower limbs from various cadavers, including gluteal muscles on a tray.

Devoid of fat - it is removed manually and with chemicals so that medical students can examine only the muscle or connective tissue - there are only patches of brownish-pink fibers.

It doesn't matter whether our butts are perfectly rounded or flat and saggy, they're all more or less the same on the inside.

6/ Your glutes are made up of three main muscles

The gluteus maximus, the largest part of your behind; the gluteus medius, shaped like a pork chop and located near the top of your hips; and the gluteus minimus, which is tucked underneath the two aforementioned muscles.

The gluteus maximus gets all the attention, but the medius does just as important a job.

Along with the minimus, “it’s responsible for stabilizing your pelvis when you’re walking or when you’re off balance,” Coach Joseph explains. Without it, you’d be swaying from side to side like a drunken sailor when you lift your feet.

Since everyone's glutes attach to the same points on the skeleton—the gluteus maximus runs diagonally from the top of the pelvis to the femur and iliotibial band on the outside of the upper thigh—if you have a high pelvis, "your posterior may have a longer, squarer shape," Kim says.

"With a wide pelvis, you can have a more horizontal orientation of the muscle." If your back is a little more curved, your butt can appear more lifted. You can work on your butt and change its size and shape (more on that later), but some people start with the beautifully rounded glutes that inspire pop songs, while many of us don't.

How much of our butt shape is predetermined by genetic roulette? According to Coach Romain, up to 70% of the overall body shape , and therefore that of your butt, is genetic.

“The rest is going to be influenced by nutrition, exercise, sleep, posture—everything outside of your genetic code.” You can thank our gender for the fact that women tend to have more posterior padding than men, and thank mom and dad for where that padding tends to congregate.

But no matter what shape your butt is when you start out, it will change later in life. According to the fitness coaches at our LE BOX DU FITNESS® store who study body shape, at the same body mass index, a 50-year-old woman has a flatter butt profile than a woman half her age, because changing hormone levels after menopause signal the body to store fat in the belly rather than the butt.

"You'll see less fat on the side of the buttocks and more on the iliac crest, at the top of the pelvis," he says. "That's why pants don't fit as well as you age."

The good news? Even with a little less padding, you can still give gravity a hard time by toning your glutes and holding them in that position.

7/ How to shape a better butt

“If you’re willing to put in the time, there are plenty of opportunities to change the shape of your butt,” says Coach Romain when I ask him if there’s any hope of plumping up my flat butt non-surgically.

In general, the gluteus maximus is a combination of fast-twitch muscle fibers—that is, fast-firing fibers, which are called upon for bursts of speed or power—and slow-twitch muscle fibers, which are the workhorses during aerobic activities.

Some studies suggest that the gluteus medius and minimus are primarily slow-twitch muscles. This means that the glutes can benefit from both high-load, low-rep strength training, such as heavy squats (to work the fast-twitch muscles), and low-load, high-rep training and endurance exercises, such as running and stair climbing (to work the slow-twitch muscles).

In fact, EMS studies have been done to determine which strength movements work each muscle, and our Sculpt Your Butt program puts these principles into practice; one flat-footed tester added an inch to her behind in four weeks.

Of course, a lot of the way your butt looks is dictated by the layer of fat that covers those glutes. "A lot of the female posterior is made up of adipose tissue," Romain explains. "The actual muscles are shaped the same as men's, although their orientation is a little different because the pelvis is slightly wider."

If extra body fat is masking yours, your safest bet for discovering its true shape is to follow a healthy 1,500-calorie-a-day diet and add regular cardio most days to lose fat all over, including around your lower half.

This combination of diet, cardio, and toning will give you the best butt you can ever have. And that's what the goal should be—not J.Lo 's or that woman who puts her head behind her ankles in yoga class.

“People say, ‘I want his butt,’ but you can’t have it, and you shouldn’t want it,” Coach Joseph says. “Instead, within your own framework, maximize what you have.” And that’s something any of us who are willing to get off our butts and move them can do.

If you liked this article and it helped you master the concept of a firm and shapely buttocks. Leave me in the comments, if you were already aware of these concepts and what is your experience on the subject.

If you want to find other Fitness and Wellness articles, take a look at the glute exercises and fitness shop sections of the blog, you will find plenty of workouts and exercises to do at home. And if you want to know more about sports nutrition (food supplements) to gain muscle or lose fat, do not hesitate to consult the collection dedicated to fitness elastics .

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