Tendinopathies and optimal loading

Overuse tendon injuries, namely tendinopathies, are a common injury in the sporting population. Endurance athletes are at the highest risk of sustaining tendinopathies, possibly due to the cumulative load applied with endurance training. The pathology of tendon injuries is complex, but it is mostly due to a disruption in the collagen structure of the tendon that gets damaged. This is likely to occur when the load applied exceeds the capacity of the tendon to handle the load, with subsequent repetitive bouts of exercise resulting in tendon structure failure.

Tendinopathies begin as a reactive tendon (swollen and inflamed inner structures), and progress to degenerated tendons where cellular death can occur. An ultrasound may reveal areas of hypoechoicity (black holes in an otherwise white looking tendon) in these areas of tendon damage, and because of the limited blood supply to a tendon, this may never change. Because the relationship between pain, function, and diagnostic imaging is inconsistent, we focus treatment on functional recovery of the tendon. For example, a highly damaged tendon on ultrasound may not present clinically with any pain or changes in function such as running.

The clinical question to ask is: how do we treat tendinopathies? We do not make decision based on imaging alone. Instead, function and pain response are a better way to treat these injuries. The old way of treating tendons involved a lot of soft tissue work to the area. This is no longer a scientific or useful way to treat tendinopathies, and if a clinician finds themself rubbing or cross fractioning tendons, they should really consider a new career! The research for tendon injury management points to exercise. We started off with isometrics, moved to eccentrics, and are now talking about slow heavy loading. Essentially, we need to find an optimal load that the tendon can handle without having a severe reaction.

When we load a tendon, there is a cellular response that occurs which is necessary to the development of new proteins in the cellular makeup of the tendon. In the first 24 hours after a load is applied, there is a rapid degradation of protein cells with a slower synthesis of new protein cells. Closer to 48 hours post-loading, we see more protein synthesis than protein degradation. Finding an optimal load means applying an exercise to the tendon that does not overstimulate protein degradation and allows enough time for protein synthesis to occur. Essentially, we are looking for a net protein synthesis response after loading. Clinically, the best way to do this is using a pain scale. Studies have shown that a pain tolerance of 1-2/10 reported the day after exercise to a tendon, is a low enough stimulus to allow for daily loading. A reported pain of 3-4 should require 1 day’s break between exercise to allow for tendon recovery, and a reported pain of 5-6 should require 2-3 days before loading again. =

The type of load used should be patient dependant. We would say that if the tendon is reactive to movement, start with isometrics, as these have shown to have good value for tendon loading response. Once the pain levels have reduced, we suggest slow heavy loading. A slow heavy load means 2-3 seconds for concentric (shortening) and eccentric (lengthening) movements. Adding weight is needed, using the pain response as a guide to how much weight can be added. Another way to add heavier loads is ballistic/high velocity movements. Tendons are most vulnerable to injury during ballistic movements (such as running) due to the high turnover of force required for such movements. Repetitive high velocity forces place extreme loads on tendons; therefore, these can be used for exercise prescription purposes as well.  There are two most important aspects of loading of a tendon: 1) progressive overload i.e. make it heavier and faster, and 2) specificity i.e. be specific about the type of movement required for the sport the person needs to do.

If you get the loading dosage right, the tendon WILL RECOVER. It must be remembered that tendons take time to heal. There is no set time limit, but it is important to create an expectation that is realistic. Encourage patience in the loading program, and measure small success regularly to ensure that progress is seen. We like to say, no matter how small, progress is progress.

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