What we would usually expect after an injury - and what happens around 95% of the time - you would get some pain at the time (sometimes proportional to the degree of injury, sometimes not), and for example after a wrist fracture, you would rest it for a few weeks in plaster, then the cast would come off and you would start to gently move it. Over a few weeks, the movement would increase and the pain would get less until a few months later - fully healed and you forget you even had an injury.
Sometimes, have an injury……..
2 major problems can occur with persistent pain; 1. Central Sensitisation Eg., who has been sunburnt on the face? Your skin is sensitive for protection. What would happen if you stood under a scorching hot shower immediately afterwards? Then as the days go on, the skin becomes less sensitive until eventually it feels normal. With sensitisation, it’s like the tissues have healed but the sensitivity remains high. What should feel like a stretch feels like pain, touch feels like pain etc.
Pavlov was a psychologist who did an experiment in classic conditioning. He had these dogs, when he showed them food - as dogs do - they drooled; and he rang a bell. Eventually after several days later, he entered the room, had no food and rang a bell. What did the dogs do? They drooled. They were associating food with ringing a bell and it caused them to salivate. So, these changes in our nervous system/body make it harder to stay active.
This si also an interesting point. They have done studies and that have shown that people with pain can simply just watch a video of someone else doing an activity that would cause them pain and they feel pain. Or even people with painful/swollen hands will get increased swelling by watching a video of someone else…. This was a study where they showed pictures of people sustaining painful injuries and measured the response in healthy subjects.
The study showed that the subjects reported subjectively feeling pain and this was confirmed on functional MRI of their brain.
We can understand persistent pain a little more if we take a look at phantom limbs. We all have a map of our body on our brain. Even those people born without limbs have a full map of their body on their brain. If I close my eyes, I know where my………… We know that the brain is ‘plastic’ and these body areas can become smudged and alter. They have shown that blind people reading braille - their map for the index finger grew bigger because they were using it so much.
It is the ability to feel sensations and pain in a limb that no longer exists (eg., changes in temperature, itching, tingling, shock-like sensations, perceived motion). Thought to be a conflict between visual/sensory feedback and proprioceptive representations of the amputated limb. The area of the brain that is responsible for processing the sensations from the missing limb are taken over by areas neighbouring the missing limb. The brain must reconcile the physical experiences of the body with the mental image, or cortical map, it has of the body. And as the body changes, this mental image can also be remapped. Here’s a true story - a rock-climber was out…...
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