In a recent article, I wrote about my first-hand experience with the Functional Movement Screen at the Michael Johnson Performance Center.

If you’re not familiar with the FMS, it’s basically a 10-minute evaluation composed of seven movements, which can expose all sorts of underlying issues in your movement patterns. These issues put you at a higher risk for injury and keep your performance anchored at sub-optimal levels, so the FMS can be a really valuable assessment tool.

The whole idea behind the screen is that the moves are simple. Hurdle Steps, Active Straight-Leg Raises, Push-Ups—these are all movements almost anyone can perform regardless of their athletic ability. But the FMS isn’t about whether someone can or cannot perform a movement; it’s about how well they perform the movement.

One movement stands out because of its incredible difficulty—the Rotary Stability test.

According to the trainers at MJPC, roughly 75 percent of the pro athletes they evaluate cannot achieve the first movement of the Rotary Stability test. Here’s what it is and why insanely in-shape people still find it incredibly challenging.

The Movement

Here’s how Gray Cook, the physical therapist who created the FMS in 2001, describes the Rotary Stability test in The Functional Movement Screen Home Study Course Manual:

“The client gets into the quadruped position with a board, either the FMS kit board or one of similar size, on the floor between the hand and knees. The board should be parallel to the spine, and the shoulders and hips should be 90 degrees relative to the torso, with the ankles neutral and the soles of the feet perpendicular to the floor. Before the movement begins, the hands should be open, with the thumbs, knees and feet all touching the board. The client should flex the shoulder while extending the same-side hip and knee, and then bring elbow to knee while remaining in line over the board. Spine flexion is allowed as the client brings the knee and elbow together. This is performed bilaterally for a maximum of three attempts if needed. If one repetition is completed successfully, there is no reason to perform the test again.”

Sounds super simple, right? It’s kind of like performing an ipsilateral variation of a Bird Dog, meaning you’re lifting your arm and leg on the same side simultaneously.

RELATED: Upgrade Your Boring Planks With These Variations

My Experience With the Test

When the trainer who was administering my screen first described the Rotary Stability movement, I thought I could knock it out no problem. Sure, I had never tried it before, but my routine includes all sorts of core stability exercises—Ab Rollouts, Planks, etc. How hard could it be?

As soon as I got into position and tried to lift my right hand and right foot off the floor, I instantly realized I was dead wrong. Just getting my hand and foot into the air in unison was a tricky endeavor. Things got even harder as I tried to extend them—my left foot involuntarily collapsed outward as my body searched for stability. Shaking, I brought my elbow to my knee. I wobbled to extend them out once again before finally drawing them toward the ground. I was clearly teetering on the brink of collapse throughout most of the movement, but I did it:

After I completed the rep, a nearby MJPC trainer spoke up and said “that was probably better than 75 percent of the pro athletes we test here.” What? How could my trembling, ugly movement possibly be anything but far below average?

Before my ego even had the time to inflate, I sank like a rock while trying to perform the movement on my opposite side:

That instantly ruled me out of receiving the highest score. (FMS movements are graded on a scale of 0-3.) I was then instructed to perform a contralateral movement similar to a traditional Bird Dog, which also required me touch my elbow to my knee. I was able to do that on both sides without issue, but the difficulty of the ipsilateral Rotary Stability test stuck with me. Why did such a simple-looking movement make me feel like an intoxicated baby giraffe?

Why It’s So Difficult

My trainer’s comment was just one of many pieces of anecdotal evidence regarding the difficulty of the Rotary Stability test.

Dr. Charlie Weingroff, CSCS, CAT and licensed physical therapist, has commented on the rarity of a perfect score. “You will know a 3 when you see it. Much like a unicorn. You know what a unicorn is? It’s a small horse with a horn sticking out of its head. That’s a unicorn. That’s a 3,” Weingroff writes on his website.  Search the words “3 on Rotary Stability” on Twitter and you’ll uncover a plethora of fitness experts sounding off about its difficulty:

Wow! Saw my first 3 on the FMS Rotary Stability. Like seeing some extinct animal or an alien. Very unusual.

— Kyle Norman CSCS, MS (@DFitJournal) November 8, 2013

Had a local D1 football prospect score almost perfect on the FMS. 1st 3 on the Rotary Stability test I’ve ever had!

— Dr. Josh Funk (@Josh_Funk) January 31, 2011

So, what exactly makes this test so demanding?

“The rotary stability pattern observes multi-plane pelvis, core and shoulder girdle stability during a combined upper and lower-extremity movement. This pattern is complex, requiring proper neuromuscular coordination and energy transfer through the torso,” Cook writes. “The test has two important implications. It demonstrates reflex stabilization and weight shifting in the transverse plane, and it represents the coordinated efforts of mobility and stability observed in fundamental climbing patterns.”

RELATED: Why Every Athlete Should Perform Ab Rollouts

As for the reasons why a person might not be able to achieve a perfect score on the test, Cook cites “poor reflex stabilization of the trunk and core,” “compromised scapular and hip stability” and “limited knee, hip, spine and shoulder mobility” as the most likely culprits. Trunk, core, scaps, hips, knees, spine, shoulders—sounds like the causes for dysfunction can be just about anywhere in the body, right? That’s exactly why the test is so difficult. The ipsilateral Rotary Stability movement essentially tests your ability to control rotational forces while simultaneously moving your limbs. It’s a skill needed in all sorts of athletic abilities, from sprinting to throwing to striking.

Andy Haley, Performance Director at STACK, explains that one point of dysfunction can lead to you failing the ipsilateral Rotary Stability movement. It integrates core stability and joint function, whereas a traditional core strength test such as a Plank mainly measures the ability to stabilize your trunk. If your core is weak or your joints don’t have the needed stability or mobility, you’ll lose your center of gravity and fail the test. That’s why so many people with good overall core strength and stability often fail at the ipsilateral movement and are forced to perform the easier contralateral variation. If everything in your body isn’t capable of working smoothly together, you’re toast.

Test Yourself

If you’d like to try the Rotary Stability test, all you need is a 2×4 board. Get on all fours straddling the board with your hips directly on top of your knees and hands directly under your shoulders. Your thumbs, knees and toes should be touching the side of the beam. Now, see if you can extend both your arm and leg on the same side at the same time. If you can, then touch your elbow to your knee, extend back out and return to the starting position.

Can’t do it cleanly enough to earn a 3? Join the club. It doesn’t mean you’re a bad athlete. Remember, many professional athletes can’t pull it off. While there are a variety of ways you can increase your odds of getting a perfect score on the test (since it involves so many areas of the body), the Single-Arm, Single-Leg Cable Row is a good place to start. Like the Rotary Stability test, it challenges you to use your core to stabilize your limbs through a unilateral movement.

RELATED: Get a Full-Body Workout With The Single-Arm, Single-Leg Cable Row