What you need to know about tendons

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September last year I attended the first Sport & Fitness Science Congress at the Sporthochschule in Cologne: a two-days event with great lectures and beautiful celebrities like Brad Schoenfeld and Alan Aragon.

The main reason for me going there – besides getting a selfie with Brad and Alan – were the lectures on tendon physiology and rehabilitation held by the world expert team of the University of Copenhagen and by Karin Silbernagel, international researcher and physiotherapist.

I expected from the Congress to meet nice people and get a professional overview about topics I already know. My expectations were exceeded! The nice people were there, and my scientific knowledge was not only updated, but I got an insight into couple of new revolutionary discoveries that open future possibilities for researching.

Here what I took home.

Tendons attach muscles to bones and joints. They are connecting structures and are referred to as “passive” structures. Muscles, on the other hand, are “active” structures because they perform movements. Thanks to tendons the kinetic force is transmitted from muscles to bones and the movement can occur. This is at least what is written on anatomy books. And in reality?

Valid scientific “tendon studies” have been carried out only in the last 10 years and have shown that our tendons are more versatile than previously thought. Tendons transmit power; they also store it, like a feather, and buffer the effect of abrupt muscular contractions. They contribute to a more fluid, coordinated and optimized movement. This is an automatic fine-tuning within our body. How we use our tendons is different and unique every time: each movement is individually and precisely coordinated and variables as gravity and internal and external forces are also taken into account.

Tendons are made of collagen, the most common protein in connective tissues. There are several types of collagen, more or less strong, more or less elastic. Another thing affecting collagen strength and elasticity is its internal fiber distribution, i.e., how they are interlinked.

Like almost everything in the human body, also collagen changes constantly. It is produced, used and recycled as needed. At the end of a long workout, more elastic collagen is created allowing smoother and more effective movements. When in a bedridden status, harder collagen is produced because movement in general looks unlikely to the body and is no longer prioritized.

Do you know that tendons do not grow? As our body becomes adult – statistically when we are17 years old- our tendons stop growing up. While muscles can theoretically grow without limit – if you get the right stimuli – tendons remain almost identical in our lifetime. Studies with the C14 carbon method have shown that our lifestyle can affect only 5% of our tendon growth.

How do tendopathies develop? Here’s an example you could be familiar with. You have started climbing short time ago – six months or so. You love it climb more than often every week. Your muscles adapted in short time, they are now climbing-specialized. You feel stronger and your movements are more coordinated and fluid.
Unfortunately, your tendons tell a completely different story. Opposite to muscles, tendons need a considerable amount of time to adapt. They simply cannot keep up with muscles. Even worse, now your muscles have become bigger and heavier and is even more difficult for tendons to properly transmit new movements. They begin suffering from the whole situation. What happens next? Right, we get an awesome tendopathy!

You might have noticed that after these 6 months your fingers have grown thicker and have interpreted it as a tendon growth but it is not correct. Would we actually measure your “big” fingers, would we find out that they have grown only maximum 5%, the 5% we were mentioning before. It seems much more because we have no much space inside our fingers and every internal structure pushes on the nearby ones. Other body parts such as the biceps grow “limit-free” because they have free space “up”. For fingers it is different: in very little space you have bones, ligaments, joints, tendon sheaths, blood vessels, nerves and many other structures. A 5% tendon increase is already enormous!

Speaking about physical adaptation to climbing. There exist indeed a finger structure that is becomes bigger: our finger bones. There is no scientific evidence that activities such as climbing or playing the piano cause joint wear and increase the risk of arthrosis. However, it has been shown that such activities reduce the inter-articular space between joints. This narrowing results in functional bone thickening as a compensating mechanism.

At the congress latest results about tendon aging were also shown. Hope is great! Collagen quantity in our bodies decreases with age, but its internal fiber structure is constantly re-organized. As a result, the aging process is minimized and tendon mechanical properties are retained. If we climb for a lifetime and manage to remain healthy and un-injured, our tendons will keep supporting us.

There are then very interesting molecules that we are just starting to research. They are called AGE, “Advanced Glycation End Products”. They consist of proteins and fats that combine themselves with sugar molecules. They appear to be a very good indicator of aging process, since they show elevated values ​​shortly before the start of a chronic disease. A lot of them is usually found in “old” tissues and organs. This is not a pure correlation because it has been found that AGE – at least in part – cause the aging process. This also applies to our tendons. An accumulation of AGE decreases tendon elasticity because it becomes for collagen fibers more difficult to glide towards each other.

It is still researched how we can prevent AGE development and what therapies can be applied to reduce it.

And here an important general note! When speaking of tendon studies, we speak of studies on the Achilles’, quadriceps´ and patella tendons. In recent years, shoulder and elbow tendons have been examined as well but no scientific studies of finger tendons have been carried out yet. It is very difficult to examine these small structures. Scientists assume that all tendons behave similarly and that individual differences have more to do with own tendon length and with shear forces.

Yes, exactly, 80% -90% of what we know about tendopathies is related to lower extremities. Research on tendons is still very young. Exciting discoveries are waiting for us!

This article is a free revision of following lectures of 24th September 2016 at the Sport Science & Fitness Congress in Cologne:

Michael Kjaer – Tendon physiology, overuse and injury treatment. From laboratory to clinic

Lauri Stenroth – Tendon’s role in sports performance

Christian Couppe – Human tendon and aging

Karin Silbernagel – How to maintain your health

This year the Sport Science & Fitness Congress will take place again at the Sporthochschule in Cologne. Christian Couppé and Karin Silbernagel will offer a 2-days pre-Congress hands-on tendon workshop. Sounds interesting!


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