Part 4 – Load Capacity
So far in our search for the tendon Holy Grail, we have covered Training Error as a cause of tendon injury, looked at the relationship between scans/imaging and rehabilitation outcomes, and lastly some treatment alternatives for tendon pain.
In this blog, we’re taking a look at the term ‘Load capacity” and if you are looking for the Holy Grail, this is probably as close as we can come to giving you some certainty! Explaining the term is relatively simple – the explanation is exactly as it sounds: what load (or resistance, or force, or stress…) is the tendon capable of absorbing without pain or dysfunction? But whilst the explanation may be simple, determining the load capacity of the painful tendon is not simple, and neither is deciding on how to progress the rehabilitation in order to improve its load capacity.
What has become clear with the abundance of research that has been completed, is that the key goal in tendinopathy rehab is improving the capacity of the tendon to tolerate the load placed through it.
The first component of any rehabilitation program should be to try and reduce pain. We know that pain causes inhibition and reduced/altered motor (muscle) activation strategies. These 
reduced patterns cause “weakening” of the tendon – or more correctly: a reduced capacity to tolerate future loading. Herein lies one of the problems – rest is often a front line defence against pain, but complete rest for tendons can be disastrous, resulting in less pain BUT a quick deterioration in the load capacity ability of the tendon. This explains why tendons with rest (even months of rest) can feel 100% better, but flare immediately when you begin activity again: the tendon has become intolerant to load! We see this happen commonly between football seasons when a footballer with a tendon problem rests all summer, feels 100% better, yet flares on their first pre season training run.
So the key, when in this early pain reduction phase of tendon management, is to also carefully manage the load on the tendon. Avoid all the activities that aggravate (modified rest), but find some activities that maintain load through the tendon but don’t cause pain! There is another buzz term in tendinopathy: the Stretch-Shortening-Cycle (SSC), which describes the spring-like stretching then shortening action of tendons to store and then release energy – this SSC usually happens at very high speed and under a lot of force, and can be extremely aggravating on sore tendons. In the early phases of rehab these SSC type of exercises (eg running, skipping, jumping, bounding etc) should be avoided at all costs if they cause pain. Whilst I’m yet to find a runner that likes to rest, it is a crucial early strategy to adopt.
To get tendons better, heavy loads are needed to promote physiological changes in the tendon that will improve its stiffness or resilience. There are many factors to take into account with strength and rehabilitation programs, with a few of the main ones being:
Where do I start?
Generally in early rehab we tend to start with either isometric strength (which is a static hold of a weight) or a long duration (slow), low to moderate intensity contractions in a (relatively) pain-free range. If single leg exercise is too difficult, we may start with double leg to begin. The key to answering this question is to find the maximum load the tendon can tolerate with minimal flare!
How many rep’s and sets?
Another question with no definitive answer. In early rehab periods, we suggest finding the maximum tolerated load that can be performed for 3 sets of 8 – 12 repetition
Functional strength or Isolated strength?
Another term used widely in strength settings is “functional strength”. There has been a strong push of recent times to make strength functional (if you are a runner, do running specific strength exercises; if you are a swimmer, do swimming specific strength exercises etc). We now know that tendons can flare if functional strength are applied too quickly in the rehab: too much load and too much bias to the SSC phase. In the final blog we’ll explain some of the isolated strength exercises that we use early on for many common tendon rehabilitation program
How much pain is too much pain?
When we’re exercising a tendon that is highly irritable (easily flared) at a level that is close to its load capacity, some pain is inevitable – we cannot expect the rehab to be totally painfree. A general rule of thumb we use at SSPC is to ensure the pain is no greater than a 2 or 3 out of 10 (with 10/10 being maximum pain) during and immediately after the exercise, and completely settles within the next 24 hours.
How much progression is too much progression?
Another tricky question but a critical one as too much progression will certainly flare. A general guide we also use at SSPC is the “10% rule” – all progressions should be not a lot more than 10%, and this 10% may be in weight, speed, repetitions. Once again you can see where it easy to go wrong – many of the pin weighted gym machines may increase from one level to the next by a minimum of 50% and more. So you need to find a way around this sudden increase in load – the tendon is unlikely to tolerate it. Even from a repetition point of view, if you’re doing sets of ten, then going to sets of 11 (not 15!) is 10%. Whilst you cannot stick strictly to a 10% rule, the point is clear: think of your increases in percentages, not just by weight or repetition.
In summary, in tendon rehab, there is no recipe, no simple way, so proven strategy. Every single tendon needs a carefully devised, constantly monitored, and consistently progressed program! This is a complex problem that must be managed on an individual basis.
Anthony Lance
SSPC Physiotherapist
