Tissue tolerance and pain
All of our tissues (muscles, ligaments) have a tissue tolerance line – for example, the amount of load the tissues can tolerate before damage occurs. Pain serves as a very clever protection system to the tissues. You can see from the picture below that the point where pain will be generated as a protection is just below the tissue tolerance line. This is useful as it helps to prevent us from injuring ourselves. The pain protection point is triggered by nociceptors (receptor cells producing danger messages) which can be modulated by attention, anxiety, and expectation.
Tissue tolerance and persistent pain
When pain becomes persistent due to the changes in the sensitisation in the nervous system, this system is altered. You would probably agree that your tissue tolerance is lower than before your persistent pain came along? This is not necessarily due to tissue damage, but due to becoming more deconditioned over time through living with pain. The biggest change is in the protect-by-pain line. You can see from the diagram below that this is much lower. This means less activity is taken to activate the pain protection system. The other thing you will notice is there is a much bigger buffer before you reach your tissue tolerance line. This is due to physiological changes in the central nervous system (spinal cord and brain) amplifying the pain protective system.
The good news
The good news is that whilst it takes less activity to trigger your pain protective system, it does not mean you are causing damage to the tissues. So the message is, it hurts but you are safe. We recommend establishing your point of flare up and your tipping point or exposure baseline. Working below this point will allow your body to become gradually exposed to the activity, improve your fitness and help to retrain the pain protective system.
Is there any hope?
Yes, it may be complex but there are things that can be done to help you. The main way forward is to try to retrain the pain system. To do this we need to look at all the things that affect the nervous system and may be contributing to your individual pain experience.