Eccentric exercise and tendinosis
One of the most exasperating things about treating overuse tendon injuries is the excruciatingly slow rate at which they heal. Equally frustrating is having to deal with the lack of acceptance of this fact by most patients.
A large part of the reason for this, I think, is that none of us had any experience with such conditions while growing up; almost all of us, however, had either first or second-hand experience with bone fractures and“know” that these generally take about 6-8 weeks to heal. This sets up an expectation that all injuries should mend within this time frame, but unfortunately, this is rarely the case when tendons are involved. Why is this,and is there anything we can do to shorten this process? Some of the treatments strategies were described in an earlier column (Article #83); what follows is a more recent approach that has gained favor throughout the physical therapy community.
Tendons – the structures that connect muscles to bones – are made up of a connective tissue known as collagen. When a tendon is first injured through overuse, these collagen fibers suffer microtears that lead to an inflammatory response, which is the natural and appropriate reaction of the body to control the injury’s damage and produce a quick repair. At this early stage, this condition is known as tendinitis.
If treated appropriately at the beginning (rest and gentle motion, primarily), most tendinitis injuries should heal within 3-4 weeks. But, of course, most runners to not adhere to that first recommendation; the continued stressful activity then goes on to cause further damage that leads to a cascading breakdown of the tissue that exceeds the body’s pace of repair. The accumulating microtears result in the production of a different type of collagen fiber to replace the normal, healthy kind. This new collagen is generally weaker, which leads to further breakdown if activity continues.
Viewing it through a microscope, this “repaired” collagen(essentially, scar tissue) now looks like cooked spaghetti rather than a nice,weaved-fabric structure with all the fibers running parallel. Interestingly,this chronically broken-down tissue shows no sign of the inflammation seen in the initial stages of the injury, so at this point the term used to describe the condition is tendinosis, which indicates a diseased or degenerative state. (The question “where does the pain come from if there is no inflammation?” is still not completely known. Some feel it is from the mechanical disruption of the tendon fibers, while others blame biochemical substances produced by the injury that irritate pain nerve endings.)
Logic tells us that the path to recovery from this condition lies in some method of restoring the health and strength of this degenerated tissue. For years, there were two schools of thought: rest or stretching and strengthening exercises. The problem with the first approach is that complete rest was found to result in deconditioning of muscles and tendons, leaving them vulnerable to further injury with even reduced activity. Stretching exercises, on the other hand, can actually cause further damage to injured,weakened tissue, while indiscriminate strengthening exercises just don’t seem to help.
The key word in that last sentence is “indiscriminate” –recent research indicates that a very specific strengthening regimen – controlledeccentric exercise – may be the answer to helping people get through this vexing problem more quickly.
The difference between eccentric and concentric exercise was described in another previous column (Article #86), in reference to the development of delayed onset muscle soreness (DOMS). In that example,eccentric exercise was seen as the villain, in that it seems to cause more muscle soreness that concentric exercise. It turns out, though, that preferentially working a muscle/tendon eccentrically, under controlled, moderated conditions, appears to have a beneficial effect on tendinosis conditions. Numerous research studies have demonstrated significant improvements in a variety of tendon injuries, including Achilles and patellar tendinosis, two of the most common conditions afflicting runners.
No one is 100% sure of why this is; the prevailing theory seems to be a belief that eccentric exercise has a greater effect on breaking down the disordered, improperly repaired collagen tissue, while stimulating the body to produce and lay down new fibers along the proper, parallel lines. Concentric exercise, on the other hand, appears to put further strain on the already injured tissue and interferes with proper repair.
The method and protocol for these exercises varies slightly from expert to expert, but the most frequently-seen program involves performing 3 sets/15 repetitions of the prescribed exercise, with moderate pain acceptable while doing so. (If pain persists or worsens after the exercise, it needs to be adjusted or discontinued.)
Rather than try to describe the exercises for Achilles and patellar tendinosis here, I will instead refer you to the following two online videos,which very nicely demonstrate the proper form and technique:
Full benefits of this program can take up to 12 weeks, so stick with it even if you do not see immediate improvements.