What is pain and why do we experience it?


We have all experienced it before: the uncomfortable low backache, the broken bone, the toe you just jammed on the coffee table. Just like death and taxes, there is something else that we all have to put up with in life and that, unfortunately, is pain. However, as far as medicine has advanced in the last 100 years, we still don’t know much about the pathology of pain.   

The Benefits of Pain

Whether we like it or not, pain is beneficial to our survival. Unfortunately, DNA, our genetic blueprint, hasn’t caught up with our current lifestyles and likely won’t for several thousand (or million) years. DNA doesn’t care that we need to sit at a desk for 8 hours or day, that we have to bend over to unload the dishwasher, or that we need to get our arms overhead to wash our hair in the shower. Our DNA is focused on three main goals and those are to find food, to reproduce, and to survive until the next day to do it all over again. Everything (and I do mean everything) in our body is designed to help us meet those three goals.  
Imagine several thousand years ago, before the desk jobs and people complaining of “text neck” existed, we had to hunt and gather for our food. Now imagine while you’re out hunting a mammoth, you fall and fracture your femur and instantly feel a jolt of pain, leaving you unable to put weight through your leg. That pain you’re experiencing is your body, and more precisely your nervous system, telling you to give the area a rest. Your body is able to heal itself. We are organic machines, able to work through every available range of motion to explore the world in order to further our three main survival goals. The pain is a signal to your body to let your immune and cardiovascular systems deliver the necessary nutrients and blood cells needed to heal the fracture and continue to survive. Nowadays, we aren’t required to hunt and gather our own food, but those biological systems are still in place anticipating it.   
What is interesting is that if you took a low back MRI of 100 active adults, chances are that a good handful of those individuals will have a herniated disc. What is even more interesting is that while some people will have debilitating pain, numbness, and tingling down one or both legs, and weakness that prevents them from doing what they love recreationally, some of those with the positive MRI findings won’t have any symptoms at all.   
So why do some individuals experience debilitating pain with a disc herniation and others don’t even know they have one? Well, it has more to do with the body’s nervous system and our perceived threat response.   

The Middle Man

Pain is a necessary topic of education for all of the patients that I work with regardless of whether they are coming in for a rotator cuff tear, ACL reconstruction, or chronic low back pain because the principles behind it are the same; it comes from our nervous system. Pain is very similar to a sunburn in the way our body perceives it. Imagine waking up in the morning, taking a nice hot shower, going to the beach and staying outside for a little too long, and then coming home and trying to take another hot shower. What happens to the water temperature? It’s probably too hot now. Why is that? Well, we have receptors throughout our body for various different stimuli including pain, temperature, pressure, vibration, etc. So when our skin gets damaged due to the sun’s harmful UV rays, our nervous system kicks in to protect our body and lowers the threshold that it will perceive a temperature stimulus as harmful.
So if our nervous system usually fires when the charge of a neuron reaches around –55 millivolts, our nervous system can actually lower the threshold to try and protect the body. That 105 degree Fahrenheit shower that you took in the morning suddenly becomes too hot and our body starts to perceive 105 degrees as too dangerous to the body. Well, pain works the same way. When our body gets injured, our nervous system lowers the threshold that it will fire for a painful stimuli to protect the area and let blood and nutrients flow to the site of injury. It’s our body’s built-in warning to itself that we need to rest. We run into problems when the nervous system doesn’t raise the threshold back up again.
When we are stuck at that lower threshold, perceiving a non-harmful stimulus as dangerous to our survival is when we start to experience chronic pain. Even worse, chronic pain is a vicious feedback cycle – we experience pain, we limit our activity, our bodies get stiff and weak from not moving, and then we begin to experience more pain. Other factors that influence the nervous system and can exacerbate or decrease our pain are our sleeping, eating, exercise, and stress habits.    

The Solution

If you’re experiencing chronic pain, it’s likely that the tissue damage that started this pain cascade has healed. It’s more common that your nervous system is in overdrive trying to protect your body from a threat that no longer exists and is interpreting regular, non-painful stimuli as painful. If you’re continuing to experience chronic pain, I would suggest making an appointment with a Physical Therapist to take a look at your activity, stress levels, sleeping habits, and a full-body examination to determine how we can get you back to doing what you love in order to keep you happy and healthy.