The Importance of Mechanoreception

by | Oct 16, 2015 | Performance Team | 0 comments

Many clinicians, therapists, coaches and trainers have expressed an interest in why we focus so much on the joints and maintaining healthy and robust articulations over the long term. To really answer this question it is necessary to provide a brief and basic review of articular neurophysiology and how this relates to our motor system and its control.
All synovial joints in the human body have two mechanisms of innervation. The first is by articular branches from both the peripheral nerves crossing the joint and by branches from the nerves innervating the muscles that cross the joint. From an internal perspective, embedded within the joint capsule are four types of receptors called mechanoreceptors, and are typically referred to as type I, type II, type III and type IV. Each of these classifications of mechanoreceptors differ in size, shape and threshold to excitation.
Importantly, these receptors provide meaningful information to the central nervous system (CNS) as it is apparent that throughout a range of motion there is continual afferent flow concerning the initiation of movement, joint position, intra-articular pressure changes, movement direction, amplitude, velocity, acceleration, deceleration, and end range position.

 

What does this mean and why is it important?

From a motor control perspective it is now generally accepted that there is no higher order that has a pre-stored movement plan for every possible joint angle or position that each joint can attain individually or in connection with other joints. Thus, under the lens of a dynamical system that is continually adapting to its internal and external environment, continual accurate feedback from our periphery is necessary to drive our motor output.

When movement is initiated there is a large burst of receptor activity in the type II receptors that provokes immediate changes in the tone of the muscles operating over the joint being moved. This has further reaching implications as this initial change in tone threshold prepares the muscle spindles and creates another mechanism of feedback to the CNS.

Throughout movement, type I receptors have a more continuous influence on the accurate muscle coordination of all the muscles functioning at that joint at that particular time in space. In essence, our CNS very quickly uses the information coming to it from our peripheral joint receptors to create necessary motor synergies.

 

What happens when we don’t have necessary and efficient joint function?

Well, first of all we lose adequate joint receptor feedback within the ranges of motion that are limited. Therefore our CNS does not get a full picture of the movement task that we are asking it to process. There is a mismatch of input and required output which leads to motor error and reduced motor variability (the ability to adapt). This also has a direct impact on spindle threshold as it is usually set to high, therefore creating muscle guarding and spasm in an immobile joint.

In addition, the type IV category of receptor, which is the pain receptor system of the articular tissues becomes activated. The result is a mechanically- and chemically- irritated joint that is a predisposing factor to the common joint issues that many of us manage on a daily basis — baseball athlete inluded.

Dr. Michael Chivers