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Why Does Good Mobility Keep Runners Injury-free?

Updated: Jun 1, 2022

Question of the year: Do you understand WHY mobility keeps you injury free?

You know you're supposed to do it, but do you understand the reason it works? Why mobility has such a huge impact on runners?

But more importantly…

How does good mobility keep me running injury free?

Are you ready for a deep dive?

Because in this blog post, I want to break down how your ability to perform this specific lunge directly correlates into your running performance.


Because this specific lunge (a movement pattern) requires mobility out of several joints, all of which need to be working at 100% for running to ever happen.

This lunge asks for full range of motion (full mobility) of your:




…with a special twist!

But before I get ahead of myself even more, imagine this scenario...

"You start to develop knee pain after your training run, and relate the pain to age, shoes, or mileage, not realizing flexibility and core strength have been on the decline.
You have been pressed for time, but not wanting to miss your running. You've been skipping your pre-run (dynamic mobility) and twice-weekly strength training.
You haven't done either activity for months and do not relate the current knee pain to the neglected aspects that once created a well-rounded fitness program.
Your life consists of sitting at a desk and forcing a few ill-prepared runs each week."

I read that paragraph in Gray Cook's book Movement, and just stopped.

Wow. How many of my patients and fellow runners on Instagram have told me this exact same story?

I realized the lesson here isn't beating the dead horse of "You need to do mobility work! You need to strength train!"

Because we already know that.

The bigger question is why don't we do it?

Easy excuses exist like, "Life got busy. Work's been stressful. I haven't had the time…"

Which is true! I get it.

But bigger truth bomb…

Life will always be crazy. There will always be external stressors.

So even after you've become a stress-managing wiz, how come you still don't hop back into that "well-rounded fitness program"?

It could be because you don't know the WHY.

Why it matters.

What it does for you.

How it helps.

How it keeps you injury free.

Because I realize, knowing you "should" do something is different than the deeper motivation, internalization, and eventually, commitment to a task after you understand the WHY.

So here's your task. Can you do this lunge?

First off: no, you don't need the special testing kit. I promise.

Second: I have instructions below to guide you through.

While doing this lunge, think of it as a TEST.

  • You're just gauging where your body is at and noting how everything feels.

  • You do need to be mindful of while performing it on both sides, that you switch which arm is on top.

  • Think of it this way: the knee that’s in front, the opposite side hand is behind your head. That's it!

  • Once you've chosen a leg to start with, place the opposite hand on the back of your neck. The other hand can rest at the small of your back.

  • For correct spacing, when the back knee is down, it should be nearly touching your front heel. Yep, it's some tight spacing.

Come on, stand up! I'm serious! Can you do this?

Can you lunge forward, back knee almost touching the ground, keeping those arms behind your back.

All without pain?

And without falling over. I should probably mention that part.

Now, switch sides and do it again

So tell me, what happened? What did you feel? Did anything feel tight? Did you feel unsteady?

Just through 1 motion, I asked your hips, knees, and ankles to move through the entire range they need so you can run.

Let's break it down.

When you performed your lunge and you bent through your front hip, you explored what we call in physical therapy as hip flexion.

When you did your lunge and bent your knees, you explored knee flexion.

Now the tricky one is the ankles. When you were at the bottom of your lunge and you bent at your front ankle, that's called dorisflexion.

You just experienced, relied on, and require ALL of these same motions you use when you run. When you lift your leg to take that first stride, that entire leg is going through those exact same motions we mentioned above. (fancy name: triple flexion)

Now for that twist I was talking about.

Can you see how that lunge starts to look like that sprinter above?

That front leg driving forward, that back leg trailing behind, and the arms moving in different directions.

The twist I mentioned has to do with that arm position.

While performing this lunge, your arms are placed in a reciprocal position. Meaning, they're not symmetrical. One is low and bent behind your back and the other is high and bent behind your head. This same reciprocal arm swing is present in a less exaggerated form while running. In this lunge, we take your arms to that extreme end and essentially "lock-up" your upper body.

I take away any balance assistance your arms might try to give you. I ask your core to stay tall and strong. And I ask your legs to control the descent and ascent out of that lunge without falling over!

It's a lot, I know! There's a lot packed into this one movement.

The question is, did your joints deliver?

Here's where the mobility factor comes into play.

If mobility is missing from one joint, your body will beg, steal, and borrow mobility from another part of your body to accomplish the task.

Don't believe me?

Let's do another experiment.

  • Do that same lunge again with your arms overhead, biceps by your arms. Note how that feels right side compared to left.

  • Now, put with arms out in front, palms up, lunge again on both sides. How did that feel? Any easier?

  • Last one! Cross your arms over your chest and lunge again on both sides. How did that last one feel?

Through all of those lunges, did it still feel like a challenge? But did you notice that as you progressively "unlocked" your arms, the easier the lunge got? You were no longer "locking up" your full amount of upper body mobility, and then asking your lower body to move through its full range. Once you "unlocked" your arms, your lower body had a little more "slack" and the lunge got easier.

But Dr. Whitt, I don't run with my arms over my head or behind my back…

Ok, you make a good point.

But like I mentioned before, you do use your arms to run. It's called arm swing. And it looks an awful lot like this reciprocal arm position.

And that's exactly why this mobility movement, this mobility test, is so useful for runners.

It assess whether you:

  • Have full range of motion of your lower body while your upper body is "locked up" in a similar pattern to the recirpocal arm swing that naturally occurs while running

  • Have the upper body mobility available to you to correctly achieve that arm swing

  • And whether you have the thoracic or mid back extension also required while running. (I know, we really took a deep dive with that one)

But can you start to see with these lunge squat sequences just how important mobility is? And how if it's missing it can result in injury because another body part has to pick up the slack?

Running is a full body experience that requires full body mobility with a special emphasis on lower body mobility. Running relies heavily on full hip, knee, and ankle mobility, just like you practiced with these different lunge variations. Without full mobility in these joints, injuries are just waiting to happen.

But what if I threw in a plot twist? What if you have full mobility of your hips, knees, ankles and you STILL can't quite nail that lunge? What if I told you the culprit may be core activation and strength?


You'll have to wait for next week for Part 2 of the Secret to Reducing Running Injuries: Why does strength training keep you injury free?

Until then, Run strong.

Dr. Marie Whitt //

P.S. Ready to jumpstart your hip mobility?

Check some fast and furious hip mobility exercises in my FREE running guide: Finding the Missing Link in Your Running and the 4 Circuits to Fix It!

Restore your hip's joint mobility before your run and maybe even follow that up some strength exercises to activate those glute muscles. Because one you create mobility, you still have to teach your body how to use it.

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