Whether you work at a desk or a construction site, walking to the bus or playing rugby, coping with some level of pain or discomfort is common. This blog explores the meaning of pain symptoms, to help you interpret when that coping is good or bad.
Does pain severity or duration measure the severity of injury that is occurring?
It might surprise you that pain severity and injury severity are not as hand-in-hand as you might expect. To give a stimulus that causes musculoskeletal pain (as opposed to psychological causes), the stimulus can be:
- Mechanical: pressure/shear/tension;
- Chemical: inflammation/capsaicin/acid etc; or
- Thermal (cold/heat).
The easiest stimulus to control is thermal. We all know that touching something around 50deg C doesn’t hurt as much as something 100deg. So, the nervous system is doing its job to give us a meaningful warning, telling us to protect from exposure to those temperatures, but it is often not as simple as that.
In research labs, thermodes can precisely control temperature of an electrode the size of a matchbox, which is rested on the skin to test the thresholds and severity of people’s pain perception. With sustained heat, approximately 45deg or more can cause a burn injury. To test the relationship between severity of stimulus and severity of pain, Robert Coghill and colleagues (2013, PNAS) applied a thermode at 49deg C. More than enough to provoke pain in most people. If we rate pain on a 0-10 scale, from 0 = no pain to 10 = worst imaginable pain, with 49deg you might expect most people to rate the pain a perhaps 4-7/10.
When Robert tested 17 people, the pain that they experienced ranged from 1-9/10. Pain is an individual experience. Sometimes the pain that you feel will give far too little or far too much warning relative to the severity of stimulus or injury.
Figure 1: adapted from Wong DL, Baker CM. 1988. Pain in children: comparison of assessment scales. Pediatric Nursing 14(1):9–17
How can pain be so variable compared to the stimulus or injury? Two words sum up an enormous about pain. Pain is predictive and protective. There are three steps that occur with most things that we feel with any of our senses (touch, taste, smell, hear, see):
- Transduction of the stimulus, so that nerves change the input stimulus to an electrical signal, much like a microphone converts sound.
- Transmission of the stimulus along the nervous system towards the spinal cord and brain, like a microphone cable.
- Perception of the stimulus, like a music editing app on a computer.
At each step of transduction, transmission and perception, signals from the body can be amplified or diminished. Then with perception, our brain and mind mix the incoming signal as well as our expectations, memories of past experiences, our social and environmental context, our emotions, even our immune and hormonal stress response systems, to make sense of what you feel. If the brain feels threatened enough by the signal, it creates a feeling of pain.
Claus and MacDonald, JDMS https://doi.org/10.12678/1089-313X.21.1.5 Adapted from Melzack Journal of Dental Education 2001, 65(12) p.1378-82.
Each of us brings our own experiences, expectations, emotions and nervous system into the equation to determine what we feel. For example, if you had previously experienced pain at your kneecap when climbing stairs, even before you take much weight on your foot to climb a step, your nervous system could produce a lot of pain to warn you. Like an alarm bell ringing, even if there is little or no new injury occurring from doing an activity as simple as stepping up.
If I’m in pain, should I train (or work)?
How do I know when pain is a meaningful warning or something I can ignore and carry on? Good question. First, a warning. It is important to check for serious pathology. Persistent pain, whether severe or not, can occur with a wide range of diseases and injuries. These require health professional diagnosis and management. Depending on the cause, serious disease / injury processes may prevent training or working as normal.
If serious pathology has been excluded and pain is not severe/unremitting, think about the activities that you regularly do that cause some pain. If your ability to do the task is declining over days, weeks or months, or if doing the task flares your pain badly and limits what you can do the next day, then it may also be important to reduce training or working to limit the flare-ups.
If your ability to do the task is maintaining from month to month, despite experiencing some pain, that is a clue that the pain may represent little or no new injury occurring, like the example of some discomfort at the kneecap when climbing stairs. Continuing to train despite some pain may be a reasonable option.
Expert physiotherapists at AXIS are well placed to help identify whether persistent musculoskeletal pain is caused by a serious disease/injury, whether you can train or work in a modified way, or continue as normal. They can design a rehabilitation program to suit individual needs, training a paced progression of loads for the body and the nervous system, to progress ability and reduce symptoms.
Expert psychologists at AXIS are also well placed to help when low mood, thoughts, memories or other feelings are contributing to what the brain does to create pain. Where the amplitude of what you feel is turned up, pain is being over-protective and limiting ability to do the activities that matter for you. Dealing with chronic pain is hard, so the advice and skills from a psychologist who has helped a lot of other people with their pain experiences can be just the right support to make progress.