Neural Factors Influencing Power

 

Raw power displayed during the second pull of the snatch.

One word that gets thrown around a lot in the fitness world is “power”.  Whether it be a goofy infomercial about some “rack” that will make you powerful, or CrossFit Football and their famous slogan, “Forging Powerful Athletes”, the word that scientifically speaking means “the applied force multiplied by the velocity of movement” (F x V), is used ad nauseum.  Yeah, I’m sure we can all agree that Hossein Rezazadeh is an incredibly powerful human being (as he is displaying in the picture above).  But what exactly is power?  In this post, we will be looking at power from a biological standpoint.  Specifically, we will be discussing the neural factors that contribute to power.

The ability to generate maximal power is not only governed by muscle mechanics and morphology (ie type of muscle action used, fiber type, tendon properties, etc), but by the ability of the nervous system to activate the appropriate muscles involved in the movement.  A few weeks back we talked about motor unit recruitment.  This phenomenon is critical to generating maximal power.  Initially, the slow-twitch oxidative fibers (type I) will be recruited.  As tension increases the fast-twitch (type II) fibers will take over.  It has been theorized that well trained athletes can actually preferentially recruit the higher threshold motor units (ie instead of going from type I to type II, they can start at type II and maximize power).

The next neural factor affecting power is the firing frequency of the motor units, as well as the synchronization of the motor units being fired.  Increasing the firing frequency can help a muscle fiber generate force in a couple of ways.  First off, increasing the firing frequency will increase the magnitude of force during a muscle contraction.  If more fibers are being “turned on”, the contraction will generate more power.  Secondly, the rate of force development will increase.  This means that more force will be generated in a quicker amount of time.  Obviously, synchronizing the firing of these motor units will help to generate the most efficient contraction possible.

Inter muscular coordination is another key factor in generating maximal power.  This describes the appropriate activation of the agonists (the prime movers), the synergists (the stabilizers), and the antagonists (opposite the prime movers).  For effective power and movement to be generated, there must be optimal activation of the agonists and the synergists, and relaxation of the antagonists.  An easy example of this is a bicep curl (which I’m sure we have all performed at one time or another!):  the biceps (agonists) contract along with some of the other stabilizers in the forearms and shoulders (synergists), and the triceps (antagonists) relax.  What are some more complex movements where this pattern might occur?

So as you can see, the ability of your nervous system to recruit and fire (in synchronization) high threshold motor units, as well as coordinate and activate the appropriate muscles, is a huge determining factor in generating maximal power.  Much of this predetermined in our genetics.  However, a well designed training program that includes heavy resistance training (because the only way to be powerful is strong), as well as ballistic training, can aid in creating a more powerful athlete (we will discuss this in greater detail in the weeks to come).

-Danny

A very special birthday shoutout to CrossFit West fire breather Anna Lutz who turns 22 today!

Workout:

Split Jerk 1,1,1,1,1,1,1 (working form, keeping weight manageable)

In between sets you can pick a gymnastics element of your choice to work on.

Anna’s Bday WOD!!! (Details to come in class)

If you have not yet signed up for the Open, you have one last chance to do it today before they release the first workout!!!