Your Leg Isn’t Going to Fall Off: How to Actually Understand Your Running Biomechanics

Raise your hand if you've ever paid $200, maybe even $500 for a fancy-shmancy gait evaluation.

(ok, if you've gotten one as part of your physical therapy treatment, you can count too)

Where you hop on the treadmill,

they take videos of you running from all different angles,

and at the end, you walk away with a mile long list of everything that's wrong with you and/or your running form.

Feels like you just paid to get insulted.

But it's supposed to help your running, right?

What you really have is a list of different joint angles, some vague understanding of "you're prone to knee pain because you overstride", and now a crippling case of anxiety that your leg will spontaneously fall off if you step wrong on your run.

As a Doctor of Physical Therapy, let me help put this into perspective.

We've been constantly told that running injuries can happen because of bad running form. However...

Your running biomechanics (aka your running form) are probably the least interesting thing about your running.

And a running form assessment can't actually tell you whether you're at risk of injury.

Don't believe me? Let's jump into it and bust these myths.

Here's What You've Been Told about Running Injuries and Running Form

"I got runner's knee because my running form was off and I was overstriding"

Seems a common enough story right? And not entirely wrong.

And it fits our "old way" of looking at running injuries, which is referred to as a pathomechanical model:

1) We attempt to predict injury via “faulty mechanics” (aka overstriding resulting in knee pain)

2) We attempt to permanently change these “faulty mechanics”

3) Usually via treatment such as gait modifications, foot orthoses etc.

The problem here is that permanently changing someone's running stride is HARD.

And often counterproductive because it can actually cause more running injuries down the road.

So while this old way of thinking, "bad running form = bad running injury", is nice and neatly packaged, it leaves out a whole lot of other factors.

How running injuries actually happen is from a training error (like too much speed work, or rapid change in shoes) plus...

• biomechanics (funky running form)

• tissue capacity (ex: weak calves)

• your unique physiology and genetics

• psychosocial influences

• energy availability (fueling)

So it's time we change our perspective.

We can still assess running form and identify which bad movement habits may be contributing to a current running injury, but we have to keep the bigger picture in mind.

Looking at running form is just ONE contributing factor to running injuries. And a better way to look at that singular part is through the load capacity model.

It helps you, the runner, more when we (PT's, coaches, etc):

1) Identify mechanics, or running form habits, that place high loads on an injured area.

 2) We then temporarily modify these funky mechanics that may be contributing to pain and injury,

3) Resulting in gait or running form changes that are actually the adjunct treatment and not the MAIN treatment.

So What Running Biomechanics Should You Actually Care About?

Let’s talk about the stuff that actually matters for your performance and your injury risk.

And we're going to do it without scaring you into thinking your foot will fall off your body.

When we zoom out, each major muscle group plays a very specific role in how you absorb load, create force, repeating that cycle with every stride.

And when something hurts, it’s usually because that muscle group’s job suddenly got way harder than usual.

1. Your Calves (Plantarflexors): The MVPs of Propulsion

Your calves aren’t just there to look good in your new, carbon plated running shoes. They’re the primary engines that push you forward and keep you upright with every step.

Your calves are working overtime when you are:

• Running fast

• Running uphill

• Running with late-stage marathon fatigue (aka the calf-cramps-at-mile-22 special)

And calf, ankle, and foot injuries are almost always related to propulsion demands being too high, too soon.

This is why runners with:

• Achilles issues

• plantar fascia pain

• shin splints

• or general “my ankles feel like hot garbage”

…usually struggle most with speed work and hill workouts. Because those are the exact conditions that load the plantarflexors the most.

What this means for your comeback is that these will also be the last things you’ll return to.

But the good news is, forward-focusing plyometrics like:

• forward pogo hops (1 and 2 legs)

• foward bounds

• Running skips (A & B)

• plus calf strength through full range like a deficit calf raise

  
  

...Are how you train it back, not pray it back.

2. Your Quads: The Brakes (and Also the “Ohhh That’s Why Downhill Hurts” Muscles)

If your calves are the gas pedal, your quads are the brakes. Their big job is to slow down your center of mass every time your foot hits the ground.

Your quads work their hardest during:

• downhill running (monster load!!)

• uneven terrain

• speed work

• and long strides

  
  

And if knee injuries feel like your constant companion, then you already know: you're more susceptible to flares when you've been tackling more speed sessions or running down hill.

(say hello to the whole gang: runner's knee, patellar pain, quad tendinopathy)

So what's a runner to do?

If you’re dealing with knee pain:

• Downhills? You’ll get those back last.

• Speed? Also last.

In the mean time? Focus on quad strength:

• Single leg box squats

• Bulgarian split squats

• and heavy step ups

...all single leg, quad-torching exercises that not just strengthen your quad, but help teach it how to brake when contracting eccentrically. Once the brakes get stronger, the red flags go away.

3. Your Hips: The Stabilizers Keeping You Upright

Let me demystify the glutes real quick, because runners often hear, “YOU NEED MORE GLUTE MAX ACTIVATION” and then immediately panic-buy resistance bands.

The reality?

Glute Max’s real job in running:

• Helps with upright posture

• Helps especially during uphill running

Yes, it’s important. But it’s not the star of the show that it's made out to be.

The real MVP: Glute Med This small-but-mighty muscle on the side of your hip:

• keeps your pelvis level

• keeps your stride smooth

• keeps your knee from collapsing inward

• helps control your center of mass

If glute med strength and capacity is low, you see more pelvic drop, more fatigue, and more side-to-side wobble.

When glute med is working it's hardest:

• Running on uneven surfaces (trail runners… hello 👋🏼)

• Hills

• general end of long run fatigue

  
  

What this means for your comeback if you have hip pain / glute med tendinopathy is that Trails will be the last thing you return to and your strength training is non-negotiable.

Because what your body is really craving is:

• Single leg glute thrusts

• forward hinged Bulgarian splits squats

WRAPPING UP

Bringing It All Together (Without Needing a Biomechanics Degree)

If you take NOTHING else from this blog, let it be this:

You don’t have to fix your running form. You have to understand where the load is going and build capacity (aka strength) there.

A good running evaluation should help you answer:

• Which tissues are doing too much?

• Which tissues need more strength or capacity?

• Which training elements aggravate that specific tissue?

• What can I change temporarily to reduce symptoms?

Not: “You're landing in heel strike positions with an estimated 5 degrees of knee extension so you’re doomed.”

When you understand the roles of your calves, quads, and hips, your running form suddenly becomes way less scary and way more actionable.

Because you’ll finally know:

why something hurts

what made it flare

exactly what to modify

and exactly how to build back stronger

AKA, the things that ACTUALLY make you faster and more injury-resilient.

Until next time running fit fam...

Dare to Train Differently,

Marie Whitt, PT, DPT // @dr.whitt.fit