The trunk creates a forward lean, twists, untwists, re-twists –
Storing up power, releasing power, storing power…

As it twists, it is planted on a leg, about to step on the other,

It untwists,
Propelling that stance leg forward as the new swing leg,

Re-twisting with the new stance leg to pivot on,
Repeating the cyclical dance between the
Torso,
Stance leg,
Swing leg.

With that twisting and re-twisting – rotational motion,
There is also a shift from side to side – lateral motion,
That loads and unloads power into forward motion
From our hips (and torso)

Via 

Drive leg (swing leg),
Trunk lean (twist), and
Pivot leg (push off).

So our hips are power transfer cases,
Translating lateral and rotational activity into forward propulsion,

But what about our knees and ankles?

As we discussed previously,
Our joints are tri-planar: they allow for movement in all three dimensions –
Forward/backward, side to side, and rotation
(Sagittal, frontal, coronal).
While they allow for 3-dimensional movement, they don’t move in all three planes equally.

A knee joint looks the most like a (door) hinge joint,
Yet it still allows for lateral and rotational movement.

The ankle does great at hinging up and down (forward and backward),
But also has lateral and rotational motion (the ankle as well as the foot itself).

While the hip is the region of our leg that converts power into motion (in conjunction with the torso),

The muscle groups down at the foot and ankle help refine motion and sense movement (and produce some power as well).

What?

Think about how much you think about moving your body when you move:
How much you think about tightening up certain muscles to create movement, and
How much you think about relaxing certain muscles to allow motion to occur.
And then think about how you time the coordination of all of these muscles – head to toe.

Not so much.

Our movement happens reflexively: A cascade of muscle activity signaled by stretch reflexes.

Think of the reflex hammer hitting your patellar tendon. The hammer is stretching nerve endings designed to sense stretch. These stretch receptors send signals to contract (or relax) muscle. In this case, the hammer strikes stretch receptors of your patellar tendon causing a reflexive tightening of your quads and relaxation of your hamstrings.

These stretch receptors are found in all of our soft tissue – skin, ligament, tendon, and muscle.
Certain motion and stretches signal for certain muscle to activate.

The foot/ankle complex is loaded with ligament, tendon, and muscle.
When the foot hits the ground, motion, pressure, and tension all happens.
Because of the way the foot is structured and what motion occurs, certain stretch reflexes are stimulated, signaling up the chain for the cascade of muscle activity to happen – laser fast.

In a way, the foot/ankle also acts as an antenna to send feedback to the power producers above regarding the state of affairs at the ground level – hard, soft, slippery, grippy, even, uneven, pavement, rocky…

Think of that epic meal at the restaurant with those friends (remember restaurants?).
Afterwards, you are all outside on the sidewalk, reluctantly saying goodbyes/trying to prolong the moment and memories.
Your back is turned to the street. And as you are talking, interacting, and connection, you step side to side, forward, and backward.
Eventually, your foot edges towards the curb. And you then step partially on/off the curb.
You don’t see it. You’re creating the memories.
But your foot senses it.
Your body was intending to take a step on solid ground.
Your foot discovered that it was only part of the ground.
Sensing the differences with the stretch and movement, stretch reflexes signal instant corrective muscle activity to counter the uneven step.
And, just as you notice you are off-balance, your body is already correcting for the curb, and a counter-step, body lean, and arm flail in the air, you regain your balance – reflexively.

Your foot/ankle complex do that on a far more anticipated scale when trail running. No longer is the ground predictable like the pavement.

Your eyes and stretch receptors help inform you of the type of effort and muscle activity it takes to keep speed up, climb and descend hills, and account for all of the small undulations that would otherwise roll and wreck an ankle.
That’s why trail running is harder. Aside from the hills, it takes far more muscle activity to account for far more movement in the other planes – lateral and rotational – and not just primarily forward. 

Yes, the foot and ankle contribute to forward propulsion, but its bigger responsibility is propagating muscle chain activity and refining motion for fluid, controlled movement and safety.

If the hips and torso are less efficient at the power and propulsion game, our bodies simply ask other teammates to help – enter muscles at the knees and feet/ankles.

If the distal muscles are asked to do more power propulsive work, they may be less good at the refining motion and sensing motion work. 

And that can further throw off muscle balance, muscle activity, timing, etc. And that opens the door for aches, pains, injury…

There is a balance of responsibility for creating movement, refining movement, and powering movement. There is a sequencing, timing, and coordination of muscle to activate and relax. And we haven’t even touched on posture, joint angles, range of motion, and other skeletal alignment and movement topics.

This running game is far more than just strong muscles, good VO2 maxes, and mitochondria. 

So if our feet do the sensing for propagating propulsion and refining motion, what about the whole shoe/insert/technology/barefoot running thing?

And what about our knees?

And what about the rest of the mechanics at our foot and ankle complex?

Great questions. And for those answers, we need more story.

copyright © Dr Adam Fujita