Brake Force at Heel Strike Does the Most Damage in Runners

One of the most important ways to avoid injury when running is to avoid braking with your feet. It is well-known that heel strike running creates a prolonged brake force at touchdown which is very destructive to the knees and hips and was implicated in causing tibial stress fractures, too.

Brake Force in Heel Strike Running

Brake Force at Heel Strike Does the Most Damage in Runners

Heel strike running is like engine braking
Heel strike running increases braking force as strike position is in front of the center of mass on the heel, causing jolting.

How does this braking force arise in heel strike running?

To initiate the next step in heel strike running, the leg swings ahead of the body. The forward-driving swing leg is usually completely straight as the knee is unbent. Meanwhile, the forefoot is pulled back to allow heel strike. What’s the big problem with this method of running?

Landing on the heel during running is like hitting the engine brake
The action of a forefoot-lift to heel strike contributes to the braking effect of heel running.

When the heel strikes the ground, the system decelerates abruptly, causing the body to come to a temporary dead stop. This produces a heavy jolt which increases in magnitude when running uphill with a heel strike –because the body needs more horizontal force to get up the hill.

Running Uphill with a Heel Strike
Because braking is greater in heel strike running, energy demands may be higher to overcome the horizontal force of an uphill slope.

Another problem with sudden braking at heel strike is that it increases frictional forces.

  • When braking occurs at heel strike, the center of mass (torso) traveling onward, collides with the leg of the heel on the ground ahead of the body.
  • The connection between the center mass and the leg act on the body to slow it down temporarily.

Because strike position is in front of the body, the center mass is above the leg’s center height, thereby exerting rotational torque on the body. To initiate flight, this rotational torque helps propel the body over the heel, over the arch of the foot, and up on the toes.

Virtually, the net torque acting on the body at heel strike produces a compressive force on the knee-joint when the weight of the body pushes down on the stance leg positioned in front of the body.

Why Elite Runners Don’t Heel Strike

Curious about the role of foot strike in performance, I noticed elite distance runners, Mo Farah and Tirunesh Dibaba, who are forefoot strikers, show heel strike mechanic similarities when slowing down when crossing the finish line (shown below).

How to reduce braking when running
Forefoot runners like Farah and Dibaba, often lift the forefoot back to brake to abruptly reduce running speed, or stop. Otherwise, they run with their forefoot parallel to the ground to reduce braking and allow smooth, non-jolted running.

When these runners slow down to stop running, they pull their forefoot back as if attempting to heel strike, and land flat-footed. Hence, the term braking with respects to heel striking.

Could the braking forces related to heel striking prevent a heel striker from reaching their optimal performance level in terms of speed?

It is often alleged, in grave error, that the role of biomechanics in performance capacity in running is well investigated, when in fact, it is vast, and we know little about it, especially the role of foot strike in speed as well as endurance performance.

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References:

Jargodzki, C. and Potter. F. Mad About Physics (2001).

Bretta Riches

Bretta Riches

"I believe the forefoot strike is the engine of endurance running..."

BSc Neurobiology; MSc Biomechanics candidate, ultra minimalist runner & founder of RunForefoot. I was a heel striker, always injured. I was inspired by the great Tirunesh Dibaba to try forefoot running. Now, I'm injury free. This is why I launched Run Forefoot, to advocate the health & performance benefits of forefoot running and to raise awareness on the dangers of heel striking, because the world needs to know.
Bretta Riches

P.S. Don't forget to check out the Run Forefoot Facebook Page, it's a terrific place to ask questions about forefoot running, barefoot running and injury. I'm always happy to help!

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