The Sensorimotor Loop & Massage Therapy
Movement occurs with constant feedback from the senses, and adjustments are made in milliseconds by the brain.
It’s important to remember that movement is conducted on a feedback loop, where the brain is constantly monitoring sensory information to help it formulate the best, most efficient motor output (physical action). Sensory information is coming from many sources, including:
Eyes, providing visual cues.
The vestibular system in your ear gives you information about balance and equilibrium.
Mechanoreceptors in your skin tell you about pressure, vibrations, and oscillations.
Muscle Spindles in your muscles sense the length of a muscle and the rate at which the muscle is lengthening or stretching.
Golgi tendon organs measure how much tension is being applied to the tendon.
Fascia mechanoreceptors measure everything from mechanical tension to pressure and pain.
Nociceptors, which can trigger pain sensation.
Information from all of these sources is constantly synthesized and filtered by the brain to plan an appropriate motor output, and all of this is happening on a subconscious level most of the time. However, when we apply manual techniques, we force some of these sensory inputs up to the conscious level. Even by simply bringing them to the conscious level, they become subject to change. An example that applies to massage and manual therapy is the use of compressions. When you compress down on a muscle, it brings a more conscious awareness of that tissue to the client. The client may now feel how much tension they are holding in those muscles and then can take a deep breath and consciously relax or reduce the tension within that muscle. That tension could potentially be limiting the range of motion, or causing ischemia and resulting in a dull ache sensation, but had you not provided the novel sensory information via the compression, the client may have never noticed they were holding that much tension.
Sensory neurons are adaptable
An example of the adaptability of sensory neurons can be conceptualized with smells. When you walk into someone's home, their home has a unique and novel smell to you. However, after a few minutes, you adapt to the smell and it no longer smells as strong, or maybe you don't even smell it at all. That’s because we adapt to many sensations. The brain filters and ignores information that is no longer relevant, in this case, the smell of the room, because it’s no longer novel. This is also kind of how muscle spindles work.
An easy example to conceptualize is static stretching. If you hold a stretch, you’ll notice that the longer you hold it, the further or deeper you can go into the stretch. That’s because the Muscle Spindles, which are constantly measuring muscle lengthening, are fast-adapting. Let me explain further:
When you enter a stretch, the muscle spindle will sense the change in length, and if it determines that you are going too far and stretching to tissue too much (potentially causing damage), it will signal to the spinal cord and cause the stretch reflex to fire. The stretch reflex results in the subconscious activation of the alpha motor neuron of the muscle you’re stretching. This results in contraction of the muscle to stop you from going any further. However, if you hold the stretch and wait, the muscle spindle will adapt (stop sending signals) and you’ll be able to go a little deeper into the stretch.
It is important to note that most of these changes are not permanent. If you stretch your hamstrings, you’ll notice an increase in the ability to touch your toes, but that ability diminishes as the day goes on. However, if you follow up your stretching protocol with exercises that also promote the full range of motion, you’ll find that you can create more lasting change.
The same is true for most manual techniques. For longer-lasting results, the client needs to follow up with some sort of exercise (strengthening or mobility) consistently to make the tissue adapt. If the goal is to increase the range of motion, many massage techniques will provide an immediate improvement, like a turbo button for results, but to make those results really stick, the client should utilize movements that make use of the full range of motion. In the same way that we do not get ripped abs and huge bulging muscles from our first-ever workout, we cannot expect the body to create lasting change from massage without the help of consistent reinforcement from the use of that mobility.
Both Soft Tissue Mobilizations and Muscle Energy Techniques are great ways to modulate the sensorimotor loop and create immediate changes in a client’s movement.