Preventing injuries is a difficult feat because there are so many different factors involved. Increasing the tissues capacity to tolerate load can help reduce the risk of injury. This blog post will define what tissue capacity is and the role it plays in rehabilitation and preventing injuries.
Tissue capacity is the amount of load that a tissue can tolerate. A simplified way of thinking of how injuries occur is when a load placed on a tissue exceeds the capacity of that tissue. The load either can be a single occurrence that exceeds the tissue’s capacity such as when you sprain your ankle, or a repetitive load such as a patellar tendinopathy. In either case, when the load exceeds the ability for the tissue to tolerate the load, injury and pain can occur.
Load > Tissue Capacity = Injury
To increase tissue capacity, load needs to be placed upon the tissue. The load on the tissue will stimulate the tissue to create more tissue. This process is called mechanotherapy (you can read more about in our blog post found here). In short, physical load placed on tissues alters the cells in the tissue which is transformed into a chemical message. The chemical message is spread around to the surrounding cells, triggering the cells to create more protein and build more tissue.
Properly loading tissues requires a balance between overloading and under loading the tissue. Overloading the tissues can cause tissue damage and prolong the healing process while under loading the tissues will not stimulate the tissues to build more tissues. As the tissues adapt, the tissue capacity will increase which means that the load on the tissues will need to be progressively increased to continue to increase the tissue’s capacity.
The only treatment option that can increase a tissue’s capacity is exercise. Ultrasound, motor nerve stimulation, joint manipulation/mobilization, manual therapy, corticosteroid or PRP injections, or surgery will not increase the capacity of tissues. This highlights the importance of rehabilitation with injuries. While the passive treatment options listed above can be part of a pain management strategy for an injury, they should be used as a means to exercise. It should be noted that corticosteroid injections may actually weaken tissues leading to an increased injury risk.
Pain can make loading uncomfortable, however, pain can be part of a strategy to increase tissue capacity. This is because the relationship between pain and tissue structure is fairly weak. This means that just because there is pain, doesn’t mean that you are causing tissue damage (although it certainly can mean this as well). In some cases, the brain can cause areas to become sensitized in an effort to protect them from harm.
Think of pain as an alarm system. The alarm system can be triggered if something is wrong such as someone breaking into a house. However, the alarm system can also alert you of someone suspicious walking around the house (could be a burglar or the gardner). In either case, the reason the alarm system is being activated needs to be investigated. Similar in pain, the reason there is pain should be investigated to see whether there is tissue damage or the system is just sensitized for protection.
Increasing tissue capacity can help reduce the risk of injuries by increasing the amount of load a given tissue can tolerate. A progressive loading program can help you safely recover from an injury or to help prevent an injury. Pain may be involved in a progressive loading pattern because of sensitized tissues, however, this does not mean that the tissues are being damaged. The key is to load the tissues enough to stimulate tissue building while not overloading the tissues.
Cook JL, Docking SI. "Rehabilitation will increase the 'capacity' of your ...insert musculoskeletal tissue here..." Defining 'tissue capacity': a core concept for clinicians. Br J Sports Med 2015;49:1484–1485.