All About Pain
Jan 22, 2023
Although pain is a nearly universally shared experience, it is a highly misunderstood phenomenon. Developing an understanding of pain, where it comes from, and why you’re experiencing it can help improve the quality of life and literally decrease the amount of pain you feel.
The first misunderstanding to clear up is the idea that pain is equivalent to tissue damage or injury. If you break your arm, you don’t feel pain in your arm. Pain, regardless of what kind of pain, is an emotion produced by your brain in response to what it believes to be a threat to the body based on all the information it has access to.
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Pain is a protective emotional response that evolved to protect us from whatever threat our brain perceives to our body.
This concept is likely easier to understand if we roll through the basics of how pain is produced:
Let’s go back to the broken arm example. Say you fall down a flight of stairs, land on your arm, and it breaks. You do not feel pain immediately. There are specific nerves that conduct signals called nociceptive signals towards your nervous system away from the site of the tissue damage. These signals are not pain signals; they are alert signals, equivalent to fire alarms. When a fire alarm goes off in your house, it doesn’t tell you why it’s going off - it grabs your attention so you can check things out. It could be something on the stove, it could be steam from a shower, or it could be an actual fire, but you have to interpret the situation the fire alarm is making you aware of. Nociceptive signals are basically saying, “Hey, Brain, something unusual is happening over here and you might want to pay attention to this.” These signals hit your spinal cord, and if there are enough of them, the nociceptive signals are passed up to your brain.
In your brain, nociceptive signals are combined with multiple other inputs you’re experiencing. What you’re seeing, other things you’re feeling, what you’re hearing, past experiences, future expectations, your current stress level, your mood, your level of fear, how much you slept last night; all of these are jumbled together. Your brain analyzes all of this information along with the nociceptive signals, and based on everything it has access to, it decides if there is a threat to the body. In this case, you would be afraid after falling down the stairs; you would look down at your arm and see it bent at an angle you’re pretty sure it shouldn’t be able to bend at; you would have a general idea that people are capable of injuring themselves falling down the stairs, and so on and so forth. In this case, certain areas in your brain that correlate to a map of your arm in the brain would light up, and you would experience the emotion of pain in order to deal with what is quite obviously a threat to the arm. The pain will keep you from moving the arm and creating further damage, and it will drive you to seek treatment in order to relieve the unpleasant emotion.
FREE DOWNLOAD: Top 3 Exercises for Top 3 Injury Prone Areas for LEOs
Once you’re in a cast at the doctor’s office, often the pain will nearly completely resolve. The bone has not yet healed, the nociceptive signals are still coming from the area, but your brain has decided the threat has decreased significantly because you understand that this is how the arm gets better. Over time the bone heals, the tissue damage resolves, you get your cast off, and you go on with your life with no further pain because your brain has no reason to believe there’s a threat anymore.
Pain is a very useful system for survival, and usually it works very well as a threat response to true tissue damage. Unfortunately, pain does not always work like this. If your brain has reason to believe there’s a threat to your body, even if there isn’t any actual threatening tissue damage, you can experience pain. This is commonly seen in long term low back and neck pain, although it can happen in any body part. In this case, pain shifts from a useful survival mechanism to a chronic pain state, in which pain is experienced in the absence of actual threat.
Let’s use the low back as an example...
Maybe five years ago, you bent forward to pick something heavy up, felt a pop in your low back, and you began to experience severe low back pain. You had trouble rolling out of bed for a week, and you may have felt shooting pains down one of your legs. Over time the pain got better, the shooting pains in your leg resolved, and maybe you did some physical therapy to get over it. However, a year later the pain never completely went away, and every so often you’ll move “wrong” or sleep weird or sit in a car too long and the pain will flare back up for a week. You go through years of the pain getting better then worse, better then worse. You’ve heard people say they “have bad backs”, and somebody tells you that you probably “slipped a disc.” Your fear of bending forward increases, and you begin to avoid it completely.
What has happened in this situation? Well, with the initial provocation of pain, there’s a good chance you may have actually herniated an intervertebral disc in your low back. For whatever reason the movement you performed created more stress than the tissue was able to handle, and the tissue became injured. Your brain correctly decided that there was a threat to the tissues in the area based on the available information and created the emotion of pain so you wouldn’t put stress through the tissue until it healed up (and recent research has shown that most herniated discs heal on their own).
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However, despite the near certainty that the actual tissue damage has healed, your pain has not completely resolved. Your brain has decided there is still a threat to the low back, has begun to pay too much attention to normal levels of nociceptive signals that you usually wouldn’t notice, and it has become hypersensitive to certain low back movements. This is called central sensitization. Your pain system has become too sensitive to normal inputs and is no longer providing useful information about a threat to the low back; instead, it is creating unnecessary hardship and disability in your life. This has real effects in your body besides just experiencing pain; your nervous system will tighten up certain muscles and limit the use of others. Muscles in your low back may tighten up, so you may not be able to bend forward very far in order to accommodate the brain’s belief that bending forward is a threat. Other muscles may not be able to produce as much force as they normally would be able to, leading to weakness and difficulty with certain movements.
In short, the stimulus your brain believes to be a threat was similar to the stimulus that could cause tissue damage, but now the trigger for pain is significantly lower. Things that we intellectually know cannot actually create tissue damage, such as gently bending forward to tie our shoes, now provoke a high level of pain. This concept can be more clearly illustrated by looking at extreme situations. In some people who have had a limb amputation, they literally have no actual body tissue in the area to send out nociceptive signals or be threatened, but they can experience a severely debilitating kind of pain called phantom limb pain in which they feel pain in the amputated limb that is no longer present. This is an occurrence of a high level of pain based on factors that have absolutely nothing to do with tissue damage. Alternatively, there are multiple stories out there of people being shot or blown up who experienced severe tissue damage but felt no pain until the more immediate threat (the hostile situation they were in) resolved. Tissue damage does not always result in pain, and pain is not always a result of nociceptive signals from tissue.
All of this leads us to an important concept that can be very helpful for recovery from a chronic pain state: there is a difference between pain tolerance and stimulus tolerance. A low stimulus tolerance would be when normal, non-damaging movement results in pain - the stimulus required to provoke pain is low. Someone can have a low stimulus tolerance, in which many things that should not hurt do hurt, but have a high pain tolerance, in which they can tolerate being in pain and still function in daily life.
So how can chronic pain be treated?
One key is in the stimulus tolerance. We find a level of stress to the tissues that your brain decides is tolerable, and we start there as a baseline. Over time, we can retrain your brain to raise that threat threshold back up to where it should be at the level where tissue damage can occur. How do we do this? In physical therapy there are certain modalities that can temporarily help - TENS unit, manual therapy, dry needling - but the long term solution is usually going to be finding the right exercise and activity dosage and progressing towards normality. Exercising the tissues creates adaptation that results in more robust tissues that are less easily injured. Loading the muscles creates stronger muscles that exert greater control over the joints involved. Easing into possibly painful movements in a non-threatening and non-painful manner helps teach the nervous system that they aren’t threatening.
FREE DOWNLOAD: Top 3 Exercises for Top 3 Injury Prone Areas for LEOs
Your brain will pick up on these changes and will begin to raise that threshold back up to where it should be, and eventually, you can become completely pain free.
Nate Jones, PT, DPT
