The Problems with a Heel Strike
This is going to seem very much like an anti-running campaign, but it's not it’s the exact opposite. I love running it’s my favourite form of exercise, but the problem is when you're given the luxury of the heel strike in a cushioned supportive shoe, things can go very wrong very quickly.
If you can change only one technical variable to make the greatest improvement to the running of any cohort of athletes take them from doing a heel strike and make everyone suddenly do a nice dorsiflexed mid-foot strike under the center of mass.
When we walk, we strike the ground with the heel, roll through the outside of the foot and then come back off the big toe as we roll through the gate cycle. That's fine, and that's the best way to control your speed; keep your balance at a low sort of intensity. But whenever you run whether it’s a 100-meter sprint a marathon or chasing after ball, the goal is to be as efficient as possible. That means any braking forces should be eliminated.
We naturally roll from outside to in (pronation) when we run or walk
Striking the ground on your heel and in front of the body is basically doing the exactly that it’s a braking force sending you backwards.
Evolution did us wrong in a whole bunch of ways; the shoulder as a ball-and-socket joint? and the VMO versus all that lateral quad mass when it comes to be keeping the patella in its groove, it’s just ridiculous. One thing that it did get right though is the Achilles-calf complex.
When we run on our mid-foot, the calf and Achilles work as a spring, absorbing and giving us back energy. Your Achilles is so strong that it gives you back 30% of the energy put into the ground back for free. That's why it’s so easy to bounce quickly up and down as opposed to going slow and using your muscles. When you bounce quick, you use those tendons like springs giving back that elastic energy.
When we heel strike instead of using the amazing rubber band system we have on the back of the leg, we put all the force into this tiny muscle on the front of your leg the Tibialis Anterior. A tiny little muscle on the front of the shin to control the foot and absorb all those ground reaction forces as the heel slams straight into the ground.
Tibialis Anterior, a tiny muscle designed to create dorsiflexion
If we’d evolved to run at speed with the heel strike, we would have a Tibialis anterior the size of the Gastrocnemius and we would have feet shaped like those old sketchy shoes.
Tibialis anterior has one small job; to lift the foot up, clearing the ground when we sprint and walk. It was not designed to absorb huge ground reaction forces when we slam the heel into the ground.
When you strike the ground with the heel out in front of the body, your kind of have to drag your center of mass back on top of the foot into that next gait cycle. Not only does it increase the amount of time you spend on the ground, it also loads your Hamstrings as opposed to your glutes as you drag and pull yourself over the foot
When you walk with a heel strike it's not that big of a deal you're only dealing with one to two times your own body weight in ground reaction forces. As you speed up and get to a running and then sprinting speed, you can be dealing with up to eight times your own body weight in ground reaction forces on a single leg with every stride. That's an enormous amount of force, and there's a lot of potential for stuff to go wrong.
When you land with a straight leg out front of the body that force is sent rocketing up the entire connect chain through the heel into the shins, the front of the knee and even to the lower back.
When you strike again on your mid-foot under the body, well, first of all, it's just less force because now you're not braking, but second, your glutes and your calves can do the work they are supposed to, working as springs to absorb and generate energy as you run.
Ground reaction force differences between a heel strike, mid foot strike and walking gait
Now here’s where shoes come in. It's not physically possible to heel strike barefoot. Those 200,000 nerve endings on the bottom of your feet will quickly tell you to change tactics and do something different. When you add the cushion of a sneaker, it blinkers those 200,000 nerve endings. Dampening the effect of the force, meaning you can run heavily and you won’t feel it.
But here's the catch just because you have a cushion in the shoe doesn't mean those forces disappear, they simply slow down. The forces are still there, you just don't feel them acutely and instantly instead the forces are passed up the kinetic chain. You don't get that immediate feedback that you would if you run barefoot and with the heel strike.