How to Do The Clamshell Exercise With Perfect Form
Here's a step-by-step guide for how to do the clamshell exercise. Try this simple exercise for strengthening the hips and protecting your knees. Plus, discover what muscle groups they work. And the #1 mistake to avoid while doing them.
By Kelan Ern Updated: 07/14/2023
The other day, I was helping a client with this powerful exercise when I told them:
'There are powerful corrective exercises floating around on the internet but people aren't doing them correctly.There are so many distinctions in even simple exercises that if you mess up - you no longer get the benefit.'
That's why I wrote this brief instructional guide:
To help you master this powerful exercise. So you know how to do it and recognize the little mistakes 90% of people make while doing it.
Before we get into how to do them - let me share a quick metaphor so you know why this exercise is needed in the first place. Because you want to know the purpose of a "tool" before you use it.
In the 1920's, the gray wolf population was nearly decimated in Yellowstone.
One reason was early park managers blamed them for causing 'wanton destruction' to the elk (and other animals). So they nearly exterminated the wolves from the area. And sure enough, over the next 70 years, the elk herds grew larger.
But that caused some unintended consequences.
These elk herds overgrazed the land which hurt the willow and aspen trees. Few trees meant beavers lost their primary building material for dams. Less dams meant the streams started eroding and becoming deeper (which hurt the trees even more).
Just like the gray wolves were wrongly blamed for problems in the ecosystem, the same goes for certain joints in the body.
The knee is one of them.
Over the years, people have asked me: How do you strengthen the knee? How do you stabilize the knee better?
The problem is they are going after the wrong suspect.
They assume that since the knee is frequently injured that something must be wrong with it. But here's something to remember:
The symptom of the pain is usually not the source of the pain.
Of course, there are exceptions to this.
For example, if you’re blind-sided by a linebacker, chances are your knee can’t hold up to this force. But outside of these collision injuries, we can prevent many types of knee injuries. And in many cases, the hips are the true culprit.
When the hips are functioning correctly, the knee tends to stay healthy. When the hips are functioning correctly, the back tends to stay healthy as well. And one of the best ways to keep the hips functioning is with something called the clamshell exercise.
So What Is The Clamshell Exercise?
Clamshells are a side-lying exercise for strengthening hip muscles. At first, this little exercise doesn't look that impressive, but it's helping you in a multitude of ways including:
Strengthens your Glutes When you do clamshells you’re activating your glutes (your butt muscles). These are important for walking, running, climbing stairs, picking up objects off the ground or even standing up. When these muscles are not working correctly, the lower back tends to compensate. When it comes to the clamshell exercise, it works not just the largest glute muscle (the glute maximus) but also a smaller one called the glute medius.
Knee Stability In seminars I’ve had audiences stand up and put one hand on their glute. Then gently move their knee side to side. When you do this, you should feel muscles in your hip activating. That’s because muscles like the glute medius actually help stabilize your knee. Like I mentioned before, many people want to point their finger at their knee for not being strong enough. But in many cases it's weak hips (such as the glute medius) that aren't strong enough to control the knee. This is why you'll see this exercise used for knee pain.
Hip Health Muscles along the outside of the leg (such as TFL-IT Band) tend to get stiff. If you’ve ever had a massage or foam rolled this area, you know what I mean. When this area gets stiff it can actually rotate the hips and cause your femur not to move correctly in the hip socket. This can cause hip pain and restrictions in movement.
However, when you strengthen the glute medius, this helps guide your femur so it moves smoothly in the hip socket. And clamshells do exactly that.
Despite it's simplicity, many personal trainers, group exercise instructors and workout buffs tend to do this exercise incorrectly.
How to Do a Clamshell Correctly
Set-Up: Start in a side-lying position with your legs stacked on top of one another and your knees bent at about a 45 degree angle.
Movement: Keeping your feet together, open your knees without rotating at the spine. Then return to the starting position. You should feel this exercise working the glute muscles. Do 10-15 repetitions each side.
Common Mistake with Clamshells
Rotating The Spine: This is the most common mistake. Make sure that only your leg is moving. Your hip should not move either. Sometimes it helps to have your hand on your hip to monitor this. Once again you should feel this exercise working the glutes.
What If I Can’t Activate My Glutes?
Maybe you don't feel it in your glutes at all. Maybe you feel it along the side of your leg (IT band area).
Sometimes it’s because these muscles have not been used in a while and are extremely weak. In other cases, it’s because your alignment is off which makes these muscles harder to activate.
Here are a few tips to help:
Tip #1: Hand on the glutes Place your hand on your glute when you do the exercise. Believe it or not, when you touch a muscle, it helps activate it.
Tip #2: Bring the legs back Another tip is instead of bending your legs forward at a 45 degree angle, you bring them backwards. Meaning: You would do the clamshell with your upper legs in-line with your torso.
Tip #3: Pillow underneath you Another way that’s worked for some of my clients is to have a pillow underneath them (right above the hips). This can help put the spine in better alignment – especially for those with larger pelvic bones.
How to Make Clamshells More Challenging
After you get the hang of the clamshell, here's a little variation exercise to try. In this video by physical therapist Mike Reinold - you'll see him do clamshells with a resistance band.
This is a sure-fire way to get your glutes working way more! You'll find even a small amount of resistance can make this exercise much more difficult.
Remember: Don't rotate from the spine (or the hip). All the motion should come from the leg.
When Should I Do Clamshells in My Work Out?
Clamshells are a great exercise to squeeze in at the beginning of a warm-up. Why? Because it activates the glutes and other important hip muscles. That way you are more likely to use them during the rest of your workout.
Meaning: your activated glutes are going to help you when you do squats, deadlifts, lunges, step ups, tire flips or other leg exercises. And ultimately that's going to allow you to get much more out of those exercises.
Do 10-12 repetitions on each side.
It’s easy to overlook such a simple exercise like the clamshell.
However, it is a powerful injury preventing exercise. It will improve not just how well you move but how well and stabilize your knees. Plus, it will positively impact the rest of your workout. Try them out and see for yourself.
In my experience, the clamshell is one of the most important exercises to have in your workout program.
P.S. If you need an extra nudge each month to help you go further, faster on your fitness journey - grab a free copy of my monthly 'coaching session' in print where I do a deep-dive on mindset, nutrition and exercise - check it out here.