Why Runners Should Do a Modified Side Plank with a Clamshell

Runners are known for their dedication and commitment — so much so that some never take a day off from running.

But there are exercises other than running that deserve just as much devotion, sacrilegious as it may seem to admit! And they can even improve running performance.

That’s why Jackie Sanders, a physical therapist and certified running coach at WAVE Physical Therapy in Cincinnati, Ohio, does a modified side plank with a clamshell every day.

To really understand why, it helps to have a quick anatomy refresher: Moving forward and backward is moving in the sagittal plane of motion. The frontal plane is your side-to-side movements, and the transverse plane is twisting movements. “Many runners focus mainly on forward and backward muscle group exercises, because running forward is generally the goal,” Sanders says. “However, the body still requires significant muscle recruitment in the other planes to prevent excess motion, which can lead to a loss of force and inefficient energy transfer.”

In other words, strengthening the muscles that help you limit excess motion while running helps you run forward with more force and more efficiently. Sounds pretty good, huh?

The Benefits of a Modified Side Plank with a Clamshell

Moving through other planes may also help you avoid getting hurt. When you strengthen your muscles in every direction, your form will be stronger, and you won’t compensate with less ideal movement patterns. That means less risk of pain and injury, according to the National Academy of Sports Medicine (NASM).

And let’s not forget everyday life requires you to move in every direction. You need to be able to twist to lift groceries out of your car and move sideways to dodge your dog as she charges in for a friendly tackle, for example.

Sanders’ go-to exercise activates muscles in your core and hips to help prevent the above inefficiencies. The modified side plank with a clamshell works the following muscles:

• Gluteus medius: One of your three glute muscles, the glute med is on the outer and upper side of your butt and helps stabilize and move your hips. The clamshell specifically targets the gluteus medius.
• Obliques: These core muscles on the sides of your torso help you rotate and stabilize your spine and keep your hips lifted in a side plank.
• Shoulders: While not the primary target of a side plank, balancing on one forearm requires shoulder strength to stabilize your upper body.

You can also use this exercise as an opportunity to focus on your breathing, another essential component of running strong. “It is a great position to focus on full inhalation and exhalation,” Sanders says.

How—and When—to Try It

Here’s how to do this exercise:

• Start lying on one side with your knees bent to 90 degrees and your hips, legs, and feet stacked. Prop yourself up on your bottom forearm, with your elbow directly under your shoulder.
• Lift through your bottom hip and the sides of your core to raise your body off the floor until you form a straight line from your head to your knees.
• Holding this position and keeping your feet together, lift your top knee as far as you can off of your bottom knee.
• Pause briefly at the top, then lower your knee back down. Repeat for all of your reps.
• Lower your body back down to the floor, then repeat for the same amount of reps on the other side.

You can do a modified side plank with a clamshell as a gentle warm-up exercise before running. Aim for one to three sets of 10 to 15 reps on each side, according to the NASM. Try adding in a few other dynamic warm-up exercises like high knees, butt kicks, and lunges for a well-rounded pre-run routine, per USA Triathlon.

To get the most out of this movement, make sure you’re not rotating your torso forward or backward, Sanders says. And don’t let your hips sag. “There should be a continuous feeling of lift from the bottom hip, with the top-leg motion remaining secondary,” she says.

If you’re having trouble holding the side plank while moving your top leg, skip the clamshell for now. Over time, you’ll build the strength to work up to the clamshell motion in this side plank position, she says. “Form is always paramount.”

Alternatively, you can do the clamshell while lying on the floor and skip the side plank. Keep your bottom arm on the floor and rest your head on it. You can place your top hand on the ground in front of your stomach to help keep your upper body stable.

When you’re ready for an additional challenge, consider adding a mini loop resistance band just above your knees. This will add resistance and make your gluteus medius work a little harder.

So, who’s up for a side plank with clamshell streak?