The Reactive Nature of Muscles

by Mitch Hauschildt, MA, ATC, CSCS

One thing that we need to remember about the human body is that the main job of muscles is to react to the environment around us.  Of course they do contract to help us create motion, but the reality is that, for the most part, our body uses momentum, inertia, and gravity to create and maintain movement through space.  And, in those cases, the muscles that surround our joints react in response to those factors to stabilize, deceleration and ultimately re-accelerate body parts.

Poor movement patterns often occur when muscles aren’t reacting appropriately to the environment.  If one or several muscles lag behind with their reaction time, problems will occur.

We can adjust the way that muscles react to their environment by improving the overall efficiency of the nervous system.  I prefer to improve efficiency with a 2-step process.  First, prime (activate) the nervous system and get it ready for complex activities.  Then, you want to groove the optimal pattern.

One mistake that many people make is under estimating the power of turning on the nervous system appropriately during a warm up or as part of an early rehabilitation intervention.  This is why we always start movement corrections with priming activities.

After priming the system, we want to groove a pattern.  We will use corrective strategies to put people in a position to perform optimal movement patterns and the then move through the pattern in order to make it the default.  The nervous system responds well to low load, high repetition activities, so that is what we want to feed it.

As part of these corrective strategies, we want to take advantage of the stretch reflex in order to help us make permanent changes by doing what I call “feeding the mistake” while grooving optimal patterns.  We know that muscle spindles prefer to be at a “normal” length, so when we stretch them, they will respond.  The brain will choose to do something to return them to “normalize” length.  I put the word “normal” in parentheses because normal is a relative term.

What the brain perceives as normal can be different for each of us and will change over time.  When a muscle becomes lengthened or shortened for a period of time, the brain perceives that length as normal.  It doesn’t know any better.  This “abnormal” length that is perceived as normal can lead to movement dysfunction.  It is a false sense what normal really is or should be.

As an example, if a person’s adductors are consistently shortened and their abductors are elongated, this will lead to a valgus position at the knee that may evolved to patella-femoral knee pain or even an ACL tear.  Most of us know this poor position for the lower extremity when we see it.  But, if you are that client and have been moving poorly for a while, it is your default movement pattern and the length of those muscles feel normal.

In this case, if we are looking to improve movement patterns, we can exaggerate what feels normal to the patient or client to the point where it feels abnormal.  At that point, the brain will realize that it is no longer in an optimal position and the natural reaction of the muscle is to reactively shorten into an optimal postural position.  If we “feed the mistake” (Reactive Neuromuscular Training) with an outside force or perturbation, we make the muscles sense their over lengthened position and reactively shorten and improve the movement pattern.

By exaggerating a mistake, we actually improve function.  I know that seems counterintuitive, but it is true.  There are a number of advantages to this approach:

• It saves a lot of coaching from the clinician or trainer. By varying the outside load on the body, we can correct movement patterns with very little coaching.  There is no need to tell them to tweak something or contract something else. Simply apply enough resistance to see the improvements you are looking for and the body will make the needed changes.
• Feeding the mistake is a “bottoms up” corrective approach that teaches the body to perform the desired task unconsciously. This is the way that we are designed to function.
• Many times a client or patient can be taught how to set up a band or other device in such a way that they can perform RNT on their own and do it effectively. It is essentially “self limiting”, which means that if you can’t perform the action correctly, you won’t be able to do it at all. It can be a great home exercise or group exercise selection.
• Research shows that kinesthetic guidance is much, much more effective with motor learning than visual or audio guidance. Using RNT to help people “feel” the proper movement patterns is a great way to use their kinesthetic awareness to your advantage.