Exercise of the year awards. And the winner is...

I was fortunate to have been back stage at the "Exercise of the Year" awards show this year. As I watched the presenters onstage prepare to announce the winner, I overhead some nervous chatter across the curtain beside me. So I leaned in, and this is what I heard:

"Oh my gosh, I can't believe it's me again this year. I mean, I know it's said that everyone gets their 15 minutes of fame, but this is going on 15 years now. What's going to happen when they finally find out I'm a fraud?"

At that point, the presenters on stage opened the envelope and announced, to great cheers from the audience, "the award goes to... once again, 15 years running, Clamshells!"

End dream sequence.

How on earth did clamshells become a thing?

They're everywhere. They've literally become one of the most common exercise names that a member of the public would know. When a new patient describes to me their current exercises, they describe most of them as "I lie on my side and turn like this" and "I go on my stomach and I arch back like this." But when they get to clamshells, they don't describe it. They just name it: "Oh, and I do clamshells."

But back in the year 2000, clamshells were known only as the hard calcium carbonate shell of a bivalve mollusk found in the ocean. So what happened?

The first sightings - "GMPs" by Shirley Sahrmann

In the 1990s, the great American physical therapist Shirley Sahrmann popularized a new method of exercise prescription. Hand drawn images of her specific exercises started making their way around the world by fax and photocopy. They had a very simple, almost iconic black-line style to them. They were nothing fancy - just a visual image to remind the patient how to do each exercise.

You'll notice the last one here. This was a specific exercise that Dr. Sahrmann popularized as a way to primarily activate the posterior portion of the gluteus medius muscle. Her point was that the hip abductors were not one homogenous collection, but rather distinct portions of muscle that had different functions. Her premise was that the posterior portion of the gluteus medius was often weak and failed to counteract the strong effect of the TFL muscle which then lead to an unhealthy muscle imbalance that could contribute to some types of hip pain.

Many of us at the time appreciated this nuanced view of exercise prescription which was unique from the standard approach taught at many universities. In fact some of us gave the exercise the name "GMPs", for "glute med posterior." But then along came the marketing machine.

who coined the term?

I worked with a PT aide in Seattle in the early 2000s. She was frank and to the point, which I loved. I would show her an exercise and I'd tell her that it's called, for example, "side lying thoracic rotation." And she would cock an eyebrow at me and say

"that's a stupid name. No one's going to remember that."

And then she'd give it a colloquial name. "That's a rainbow exercise," she'd say. And of course, when I showed her what I called the GMP exercise, she said "no it isn't. That's a clamshell." Now I don't think my good friend Robin invented that term. I just think that most creative-minded people saw that exercise and recognized what it reminded them of. I'm sure the name was coined independently by hundreds of people in the early years, and it just spread. In 2025, no one calls it anything else but clamshells.

So what's so wrong with this exercise? For starters, when you understand the actual function of the gluteus medius (G Med), the clamshell exercise has no face validity at all. It's a non-starter, and here's why.

conventional nomenclature messes us up.

Here's a question from your undergrad anatomy course. Give your immediate answer without thinking too much:

What's the bony origin of G Med?

If you answered the iliac fossa, congratulations. You just passed every anatomy exam ever.

If you hesitated and had to think about it - that's great progress. You're starting to think outside the box a bit.

If you answered the greater trochanter, even more congratulations. You probably already understand the main purpose of G Med.

The standard protocol for naming origins and insertions typically uses the proximal bone as the origin. The proximal bone is supposedly the stable base that allows the muscle to move the distal bone in space. That naming convention works for many muscles, much of the time. But if we consider what it does all day long, the G Med doesn't fit this pattern. It does not primarily work off a stable pelvis to move the femur. It works in reverse.

How to imagine G Med and what it actually does.

The number one function of the G Med is as a frontal plane stabilizer of the pelvis in single leg stance. Here's another quick question:

For how many minutes do most people stand on one leg in a day?

It's a bit of a trick question, since we need to consider that walking is a single leg stance activity. From there, it's simple math: If one achieves 10,000 steps in a day, that's between 90 minutes and 2 hours for most people. The single stance phase of gait takes up 40% of the gait cycle. The answer therefore ranges from 35 to 60 minutes of single leg stance per day.

Imagine that. G Med is working hard executing it's primary function for up to an hour per day.

In the case of G Med, the femur is the stable bone. The pelvis is the moving bone. If you're a physio, the image below needs no description. But to a patient I might explain it this way:

Gravity (yellow arrow) The pull of gluteus medius and TFL (green arrow)

When standing on one leg, the pelvis tends to tip down on one side because of the line of gravity passing through the midline of the pelvis. It's like taking one leg off a table - it's going to tip that way. That's why you have a G Med - it contracts strongly in single leg stance (along with TFL) to keep the pelvis level; in effect, to stop it from moving.

Here's another way of thinking of it. Imagine the G Med as a person standing on the trochanter - the solid stable base. Imagine they are reaching up to the side of the pelvis and pulling down as hard as they can to stop the pelvis from tipping sideways.

Therefore, the G Med primarily acts in a closed-chain position, performing an isometric contraction during full weight bearing. Nothing about that resembles the clamshell exercise. So why would we train it in a way that is so contrary to its function?

I choose not to go to the research on this question. One key question to ask when deciding whether to read a study is whether or not the research question has, on the surface "face validity". Definition: whether a test or measurement appears, on the surface, to measure what it's supposed to measure, based on subjective judgment from users or non-experts, making it seem relevant and appropriate. The question of how the clamshell exercise compares to closed chain hip abductor strengthening in improving weight bearing strength does not appear in any way to be a reasonable question to ask. We know better.

Cultural literacy

When, precisely, in our lives to we need strength in this position?

As always, the fitness industry picks up on trends and doubles down on them, deeply embedding them into the cultural awareness even when they are off-target. Clamshells may be one of the best examples of this in recent memory. It's going to take years, maybe decades for the public literacy to change.

If you're a swimsuit model, the clamshell exercise is highly functional.

Here's an article published online in 2024 by the immensely popular fitness brand Peloton. It's called "Why You Should Be Working Your Gluteus Medius—Plus the Best 8 Exercises to Target It." Clamshells are number 2 on the list. Not one of the 8 suggestions targets the GMed in its primary roll as a frontal plane pelvic stabilizer in closed-chain weight bearing. Not one.

How many clamshells must this guy have done? MILLIONS!

How then shall we proceed?

The point of this blog isn't to go into great detail on how to properly strengthen the hip abductor system. We could spend a whole day on that. The point here is to swim upstream against the current. Everyone these days is clamshelling their way to hip mediocrity. We know better.

I bet if you took 90 seconds right now, you could come up with half a dozen really effective exercises to strengthen the G Med in a closed chain weight bearing way that will be effective for your patients.

SUMMARY

Thinking of a new year's resolution for your clinical practice this year? Keep it as simple as ABC:

Anything But Clamshells.

Jeffrey Begg, PT

Clinical Specialist (MSK)