To navigate a changing, unpredictable and sometimes dangerous environment, our sensors need direct control over our muscle tone.
Immediate Protection Without Thinking
When you touch a hot iron, nerve messages race up your arm and into your spinal cord where they connect directly to the motor neurons that contract the muscles which pull your hand away from the iron, even before your brain registers that there is a problem.
Without a direct connection between your skin and your muscles, the pain warning would have had to travel all the way to your brain, be interpreted and wait for you to send messages to your arm – wasting valuable milliseconds as your hand sizzled.
How It Works
If you stand on a nail, pain sensors fire causing contraction of the hamstrings and hip flexors, lifting your foot off the nail. At the same time, the antagonists are inhibited, preventing you from pushing your foot further through the nail. The sensors that detect the damage to your tissues stop you walking (and therefore prevents more damage) because they change your muscle tone.
The direct link between your skin and muscles is called a reflex. In this case, the withdrawal reflex.
Beyond Pain: Responding to All Irritation
You probably recognise the withdrawal reflex in the feet (standing on a nail) and hands (pulling away after touching a hotplate) but it operates throughout the body, even if the stimulus is not painful.
A pebble in our shoe doesn't really hurt, but we stop and take it out as soon as we can. Otherwise we would limp.
Notice that it's the reflex which controls your movement, not your brain. The reflex HAS PRIORITY over your brain's conscious instruction, which is why it's impossible to force yourself to hold your hand on a hot iron.
Our nervous system hates irritation. Our skin needs to be free of insult for us to be at peace and able to function normally. It's not just princesses who are bothered by peas.
The Withdrawal Reflex at Work
Our skin is so sensitive that it can feel one hair move. If our sensors are alerted to any irritation, they ready us for action, by changing our muscle tone.
The irritation doesn't have to be painful. Tickling is a very effective way of activating some muscles while inhibiting their antagonists.
Real-World Example: Belly Piercings and Back Pain
If you put a piercing through skin around your belly button, it will activate your abdominals and inhibit your spinal extensors, the ones that hold you upright.
You will feel perfectly normal until the next time you have to lift something heavy, when you may well sprain the joints of your low back. Unless you take the belly piercing out, your low back pain might never go away.
Physical Therapies and Afferent Input
Afferentology provides a common understanding of the beneficial effects of all the physical therapies, from reflexology to yoga, chiropractic to physiotherapy, Qi Gong to aerobics, Pilates to Shiatsu.
Any practitioner who touches, moves, pokes, prods, adjusts, manipulates or mobilises a patient is altering that patient's afferent input.
Understanding Reflexology
When a reflexologist rubs or stimulates points on the feet they are activating sensory receptors in the skin, fascia and muscles of the feet. This stimulation facilitates some muscles while inhibiting others, creating measurable changes in muscle tone throughout the body.
Acupuncture Explained
Acupuncture can likewise be explained in terms of skin receptor stimulation. The insertion of needles induces the withdrawal reflex, but this time the effects will be more specific and far more powerful than simple pressure on the skin because the needle may physically damage free nerve endings. The stimulation from those nerve receptors may last hours to days after the needles are withdrawn.
Foreign Bodies and Long-Term Effects
Afferentology offers an alternative explanation for the practice of acupuncture and leads us to look for the effects of other foreign bodies we commonly leave in the skin.
A nail in the foot is the classic example of the withdrawal reflex, but a nail through the ear or the nose will also produce facilitation of some muscles and inhibition of others.
It is impossible for an earring not to induce muscle tone changes as the body withdraws from the irritating foreign body. Once we are aware that these changes are inevitable, it would be negligent not to examine for it as long as the examination is appropriate for inhibition.
Learn to Identify and Address Withdrawal Reflex Issues
Discover how to examine muscle tone and identify sources of nerve interference affecting your patients.