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‘Pain is not the only problem’: Afferent Signal Loading, Part 2

Afferent signaling describes the sense-signals of tissue origin associated with touch, temperature, vibration, joint position, muscle work, and the idea of ‘pain.’ Sense signals of ‘pain’ are commonly associated with tissue damage, such as traumatic injury, acute healing, non-traumatic conditions and diseases; however, the commonest presentation in LBP is a dull, achy, broad/diffuse annoying discomfort, and occasionally with a sense of radiation, sharpness, pinching, or tightness. In grad school they taught us that different kinds of pain can describe different kinds of low back injuries, and while that might be true in theory, I found to be less helpful in practice. I found that regardless of the patient’s description of the LBP it was not helpful in determining the diagnosis.

In Part 1, I presented a basic platform to explain how nerve diameter size + number of motor units fired by that nerve + the muscle tension associated with that nerve determines the ‘loading’ sequence of the nerve. Certain nerve sense-signals are prioritized, loaded first and arrive afferently at the cortex first.

The priority loading order goes like this:

First: Aγ fibers/muscle spindles: muscle’s speed of shortening (+isometric and slackened states)
Second: Aβ fibers/golgi tendon organs: tension on tendon (~muscle) GTOs are non-contractile
Third: Aβ fibers/vibration, joint position: includes the inherent oscillation of muscle contraction
Fourth: Aβ fibers/deep dermal pressure, broad dermal pressure, 2-point discrimination
Includes: light touch, slick/smooth, rough, palpation identification
Fifth: Aδ fibers/temperature, wet/dry, sharp and pinch ‘pain’, spicy ‘pain’
Last: C fibers/slow ‘pain’, dull, achy, burn, gut ‘pain’ and deep pressure

It’s no wonder why therapists use cryotherapy and heat as a treatment since this sense-signal is loaded before pain; the brain is paying more attention to the temperature than to pain. Better yet, light touch is loaded before temperature. Deep-tissue massage is not as successful as light massage since it is loaded after light massage. In theory, light massage should give better ‘distraction’ than hot/cold therapy. I use the word ‘distraction’ rather than ‘loading priority’ in my everyday conversations with patients. Distraction means that I am managing the experience of my patient’s brain by asking their brain to ‘listen’ for something other than pain (being the lowest priority.)

‘Listening’ means that the patient’s brain is focused on a therapy/sense that is the highest priority since it is loaded first, second, or third, or all three top priorities at once. However, the ‘distraction’ technique does not cause healing, or provide a palliative effect for much longer than the treatment time; there are no lasting effects. Techniques like ART, MFR, and foam rolling only cause more tissue damage, delay healing, and are loaded at the last priority (no benefit.) Why would sports taping provide some relief?

Critically thinking, we can begin to understand why LBP patients suffer more than other chronically onset complaints. Chronic low back pain forces patients out of activity, exercise, and even usual ADLs. When movement begins to vanish from the LBP patient’s lifestyle, muscle activity dwindles or ceases, especially concerning core-activation, and use of the largest motor groups (hip flexors and extenders, spinal erectors, glutes, and lats.) When core-activation ceases, the transversus, the urogenital diaphragm (pelvic floor), the multifidi, and the respiratory diaphragm weaken, and become less responsive to spinal loading and to providing spinal stability. The LBP patient is not providing core-activation, and larger muscle groups sense-signaling diminishes.

Just as it is possible to get the brain to ‘listen’ to light touch to give palliative care by providing a higher priority sense signal, when a higher priority sense signal is missing, it causes the lower priority sense signals to be prioritized. If the first 3 priorities are missing, and in the absence of thermal treatments, and massage… the only priority remaining for the brain to ‘listen’ to is ‘PAIN!’

LBP patients are in chronic pain because there is nothing other than the ‘pain’ sense-signal to listen to. This kind of listening has consequences. The brain starts to assign the pain sense signal to the fifth priority, so temperatures become painful, then to the fourth priority, so deep touch becomes painful, then to the third, second and first. At this point all core-activated and large motor group movements become painful, and the therapy is at a stand-still… well, not really… keep reading the articles.

This article’s message is to discuss the importance of understanding why the priority of sense-signals can, on one hand, explain why certain therapies might offer palliative aid, and on the other hand, explain how chronic pain develops. Now, it should be very clear that ‘pain is not the only problem.’

LBP Blog General information

Series Description

These articles intend to (1) re-evaluate the prevailing clinical practices thought to manage low back ‘pain’, (2) submit and debate novel low back ‘pain’ contributors and mechanisms, (3) meet patient expectations & satisfaction and clinically meaningful results, (4) recommend a conservative non-surgical course of care to over-ride ‘pain’ instantly, and (5) restore ADLs and patient confidence on the first visit at low cost. This article has a companion podcast.

Dr. Dean Bio

Forester Dean is a chiropractic and physiotherapy sports medicine doctor practicing in Los Angeles, California. Dr. Dean is a lifetime athlete, and currently teaches tennis, track, boxing, yoga. The Core X System™ Campus flagship location was opened by Dr. Dean in 2020. www.preformancecxs.org

© Copyright 2021 SpineSync, Forester Dean, DC
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