The Science of Pain

The Inflammatory Process and Pain 

There are two main types of pain; 

1. Acute Pain – is there to tell you to stop in order to prevent more tissue damage.
2. Chronic pain – is where we don’t really know what the stimulus is? We feel like there is tissue damage but not sure what it is causing it.

Usually after acute pain that hasn’t been controlled or managed. The stimulus amplifies itself and chronic pain ensues. 

Acute Pain – Peripheral Sensitisation

When we get hurt and inflammation arises (heat, swelling, redness, bleeding, pain). Many different types of cells (mast cells, neutrophils, T Cells and macrophages etc) are released in order to deal with the inflammation. 

The cells will release pro-inflammatory chemicals. Different types of chemicals will have different effects on the pain receptor which will send messages to the spinal cord and then the brain. 

Hydrogen ions (H+), substance P, ATP and serotonin bind to nociceptors (nerve cell for pain) and open channels to allow positive ions in such as calcium and sodium. 

Nerves have a charge difference. Inside it is -90mv; as positive ions flood in and make the cell more positive and it rises to -55mv, it opens sodium channels allowing sodium ions to flood in actioning a signal to the spinal cord (action potential). 

So to send a pain signal, the nerve cell needs to become more positive inside. 

Other chemicals such as Bradykinin, Histamine, Nerve Growth Factor and Prostaglandin are pro-inflammatory and they act to sensitise the neuron and make it even easier to make the nerve cell positive inside and send a pain signal. This means that only a small amount of positive ions would be needed to generate an action potential. 

When you stimulate a nociceptor to create a pain signal it also releases chemicals called neurogenic inflammatory chemicals which include Substance P, CGRP, cytokines and chemokines. These stimulate the process even further. 

While the stimulus is still there, the process continues in a cyclical manner until you remove the stimulus.      

When Pain becomes Chronic – Central Sensitisation 

Once the pain signal has been sent to the spinal cord, the receiving neuron will send the pain signal to the brain. However, between the initial pain cell and the receiving neuron many substances are released such as Substance P, Glutamate, CGRP, cytokines etc which amplify the signal even more. 

The initial stimulus can be stopped and peripheral sensitization stopped however the central sensitization can still continue even without a known stimulus and this is where we get chronic pain.  

As the substances can drop the threshold for pain, it means even a light stimulus can trigger a pain signal to the brain

Research suggests that trigger points can initiate central sensitisation, as well as that central sensitisation can promote trigger points.  

How can pain be helped?

When we hurt ourselves, usually our instinct is to grab or rub the area. Research has shown that massage can significantly reduce pain levels as well as enhance wellbeing and speed up healing.  

Massage and acupuncture has been shown to ‘close the pain gate’. It will stimulate the large nerve fibres that compete with the nerve pain signals described above. In essence it ‘blocks’ the signal and changes how we perceive the pain.  

Massage also reduces cytokines which is one of the neurogenic inflammatory chemicals.   

Acupuncture and cold laser work similarly to produce pain relieving chemicals such as endorphins.  

Improving blood flow helps relax the muscles and reduce spasm. It also brings nutrients such as oxygen to the area to help with healing. Improving the movement of lymph and the debris left behind during the inflammatory process also enhancing healing and pain reduction. 

Where we can reduce stress, enhance mood and sleep will also help with chronic pain – take a good look at the six doctors of life and to see if they are balanced – rest, diet, exercise, socialising, sunlight and hydration. When these are unbalanced, we promote inflammation in the body making the pain cycle harder to break. Stimulating the vagus nerve helps engage the parasympathetic nervous system which helps control the ‘rest and digest’ function of the body, counteracting stress and inflammatory producing signals.  

When pain becomes chronic we learn to expect the pain. NLP can help unlearn or learn new thinking patterns to help restore the mind-body relationship.

The same goes for animals; are their needs been met so stress is reduced? Pain can become chronic and cause behavioural and compensation issues. Where the painful source has been eliminated, we still need to address the pain memory; both mental and physical. The body adapts for survival. Confidence to do the things that previously hurt may need to be built.   

If we can reduce pain, we can enable movement, once movement is enabled then pain is reduced. This is why manual therapy and exercise therapy should be combined.