Gait Analysis: Core Stability vs. Core Action

In the video above you’ll see me running two ways, revealing a surprising effect of trying to hold your pelvis still: it reduces the mobility of your legs.

This video is the second in my series of gait lab videos. All the runners in these videos are me; one of the perks of being a Feldenkrais practitioner and former dancer is that I can easily manipulate my running technique to show you different things. And having myself shown as essentially a stick figure (thanks to a Qualisys motion capture system) can make it easier to see some things than a live action video would.

In the segments I call “core stability” I’m trying my utmost to hold my pelvis still. You’ll see it can’t actually be done, but the movement is reduced compared to what I normally look like (take a peek at the previous video to see that).

In the segments I call “core action” I’m thinking of actively moving my pelvis. Most running should take place in between these two extremes, allowing your pelvis to move without doing it intentionally. However as you can see, actively moving your pelvis (once you’ve properly learned how) is a great trick to have in your bag for when you really need some speed.

Now a word about the term “core stability.” Many clients come to my office with the idea that good running technique requires holding your pelvis still, and that doing it is called “core stability.” They think this because many fitness and health professionals tell them so.

Fundamentally that’s a misunderstanding of the concept, and if you want to learn more about the true definition of core stability I highly recommend watching this 10-minute video interview of researcher Paul Hodges.

However I think the very term “stability” helps create the misconception that the pelvis and spine should be held still, and I don’t think it serves runners. Or for that matter any people who need to move, and that would be everybody. It’s a poor choice of words.

So because “still” is the most common interpretation of the word “stability,” I use it that way. And to talk about the right kind of movement for running (or as Hodges would put it, the right balance between motion and stiffness) I use the term “action.”

To read more about the movement I call the “core action,” take a look at this post.

Now back to the videos. Though I was unable to stop my pelvis from moving in the “core stability” video, I did reduce its movement and this had a huge effect on the way my legs worked. To be honest I didn’t suspect myself how large the effect would be and was amazed when I saw the video.

My stride rate is the same in both videos, but in the stability video my stride length is considerably shorter. My swing foot doesn’t come up as high, my stance knee is less bent, and it may also be that the stance foot is in front of rather than exactly underneath the hip joint in midstance, though I’d have to see the sagittal view (from the side) to be sure.

And to top it all off, I was working noticeably harder in the stability run. Trying to stop your pelvis moving isn’t easy, and it’s also very distracting from the main task of running.

Runners who are trying to maximize their performance these days often work on their stride length. There’s an idea that the legs and the “core” work independently, so if you want to increase your stride length you should focus on improving your hip joint mobility — perhaps even while attempting to hold your pelvis still so you can be sure you really are getting full hip joint extension.

But you can see from this videos that in fact stride length benefits from a more mobile rather than stable pelvis. A narrow focus on hip joint mobility misses a powerful opportunity to lengthen the stride. Runners who work on stabilizing their pelvis may well be reducing their ability to use their legs well, harming their performance, and worst of all, making running much less fun.