I amaze myself sometimes. Not that I have any special abilities, I can’t parkour up the side of a building, backflip my way through an olympic gymnastic competition, or get out of bed in the morning without groaning. But some movements that I, like most of us, can do with just a little practice, are more complicated than they seem on first pass. I am amazed that anyone can do something like a karate kick, for example, when we look at what is required from our nervous system alone.

I have been taking karate for a few years, and one of the first moves I learned, maybe even first day, was a four count stepping front kick. 1) Pick up your leg up thigh parallel to the floor, knee at 90. 2) Extend your leg, keeping your thigh parallel to the floor, flex your foot, extend your toes 3) Retract your leg to position (1). 4) Put your foot back on the floor. Sounds simple enough, even for me. But how do we initiate and execute that kick? How do we hear a command for a front kick, understand what that means, and then convert that into action? Or how do we know during a sparring match, for example, that we now have an opening or have created an opportunity for a stepping front kick?

Even a seemingly basic stepping front kick requires a complicated and highly coordinated set of signals within our nervous system, and from there to our muscles, more so that would be imagined from watching even in the most awkward looking of kicks. Millions of neurons in our brain down through our spinal cord and extending into our legs, all the way down to our toes, are firing long before the first muscle fibers even twitch. Then, when we finally start the kick, feedforward and feedback loops within our brain, and between our brain, muscles, and sensory nerve endings in tendons and joints fine tune the magnitude and direction of our kick. Protagonist muscles, the ones that facilitate the movements in our kick, are contracting, at the same time antagonistic muscles, the ones that directly oppose the movement are relaxing, and stabilizing muscles are keeping the kick steady. The timing has to be perfect or instead of a stepping front kick, we could end up in a twitchy floor spasm, which, as far as I know, isn’t a part of any form, unless maybe someone is being trained wrong on purpose.

The story of our front kick, this complex movement involving millions of neurons (which would stretch over miles if laid end to end) in our brain, down our spinal cord, running all the way down to our feet, and muscles in our back, abdomen, and both legs starts with just the smallest of shifts of sodium and potassium across a nerve cell membrane in our brain.

A good narrative, at some point, gets interrupted with a backstory to bring more depth and meaning; the story of our devastating front kick is no exception. Unfortunately this one does not include any radioactive bug bites or set up revenge plot, but there is still some basic neuroscience and neuroanatomy to help understand how our kick is going to happen.

How the image of our partner hits the back of our eyes and triggers a set of signals there that follow a circuitous path starting from the backs of our eyes, cross to the opposite side and, bounce to the back of our brain, splits, and bounces forward again. That signal is integrated with other sensory inputs, memories, and signals from other areas in our brain, cross again, is then sent down our spinal cord, and finally heads out to our muscles, to be constantly adjusted through feedback loops from sensory nerves.

Next week we will cover some of the neuroanatomy and neuroscience involved in our front kick.

Thumbnail image courtesy of sefcmpa at wikimedia commons