Pain - Where Does It Come From?

We all know the feeling of intense physical pain – from stubbing your toe to burning your hand. Have you ever been trapped on the floor by back pain, with a spasm that subsides after a few days? Do you know where this pain comes from? And why some of the smallest injuries, like a paper cut, can seem to cause the most pain.

What is Pain?

Pain in all its varieties is one of the most complex human symptoms, making it sometimes very hard to diagnose. It is defined as an ‘unpleasant sensory and emotional experience with actual or potential tissue damage’[1]. It is clear by this definition that there is a multi-dimensional nature to pain and that it is, most importantly, a sensory experience. But it also has an emotional component which is key to be aware of.

 The feeling of pain occurs due to a cascade of events, starting when specific nerves called nociceptors are stimulated. One reason for the activation of these nerves is tissue damage. They transmit a signal to the brain, along the spinal cord. The brain will then assess what reaction is required, sometimes initiating an immediate reaction in our muscles. For example, you touch a hot surface, your hand will reflex and recoil from that surface.

Cascade of events, starts with nerve stimulation & finishes with a response, like pain or movement. Adapted from [3].

 Pain is a primal instinct and is another such response triggered by the brain, with the sole purpose of notifying the body’s defence system to react to avoid any further damage. The brain doesn’t only use information from these nerves to protect you, it will also use knowledge, past experiences, and emotions to detect possible danger. Think back to the hot surface, have you ever moved your hand quickly away from a commonly hot surface, like a kettle, only to find it's cold?

 This is why some of the greatest continued pain can in fact come from the smallest injuries (back to the stubbing of your toe incident) or indeed when there is no injury at all, like a muscle spasm in your back.

A route away from painful injuries

As a sports therapist, I am trained to understand my client’s route to injury and therefore why their body is presenting painful symptoms. My training has been focused on prevention, assessment, treatment, and rehabilitation, ultimately working with my client so they can return to their chosen exercise or sport.

Finding what is triggering your pain, whether it’s a muscle, joint, bursa, ligament, or nerve, or even whether your knowledge, emotions, or past experiences are contributing to sustaining your pain.

But what if my pain has changed?

When injuries become persistent, the commonly accepted pathway of nociceptor nerve stimulation = pain becomes blurred. Pain can increase even without (more) tissue damage, and this is due to other factors altering your perception of the pain and how your brain interprets the information it has available.

In fact your brain can ask nerves to respond sooner if it thinks there might be on-going danger. Have you ever Googled an injury and come away thinking about the worst-case scenarios? It’s a fact that any pain that triggers higher negative emotions (like reducing your ability to work or being able to participate in your desired exercise routine) will be perceived to be greater than the same injury without the emotional stress.

 It is also true that the longer you have pain, the better the nerves and brain become at reacting to it. In effect, the nervous system lowers its threshold for stimulation and the brain reacts faster to stimulus from that area.[2]

Image 2: Overtime, without resolution of pain, the brain will lower the threshold for nerve stimulation.

Rehabilitation is the route to recovery

And that is why it’s so important to not only rehabilitate the injury but to talk through everything. Educate to give knowledge that breaks the cycle of pain, rather than feeding it.

 Recovery is often overlooked, with a training route back to exercise the most important way to ensure painful injuries are a thing of the past.

References

[1] Merksey, 1996

[2] Peters ML. Emotional and Cognitive Influences on Pain Experience. Mod Trends Pharmacopsychiatry. 2015;30:138-52. doi: 10.1159/000435938. Epub 2015 Sep 18. PMID: 26436897.

[3] Martins D. Chapter Twelve - Serotonin and nociception: from nociceptive transduction at the periphery to pain modulation from the brain. 2019.