# Tendons 101



## Mythos (Aug 29, 2017)

I have recently been having some elbow tendon issues and it’s given me some extra free time. I figured I might as well use that time to do some research on tendon injuries and see if there was anything I could do to accelerate the healing process. After reading a bunch of scientific papers and parts of a medical book on tendons, I found out that medical science still has a lot of questions about recovery from tendon injury. 

Apparently tendons are strange beasts and the healing process is really complicated. For this reason, there’s a ton of contradictory information coming from studies on the healing process. For this thread I tried to keep the information to what is pretty well known and shown to be true again and again.  I also kept my research to injuries that aren’t so bad that they absolutely require surgery, because I want to know what I can do outside of the Dr.’s Office.   Here’s what I learned:




First, What are tendons? Basically, tendons are the tapered end of the muscle that attaches to the bone. There is no clear point where muscle becomes tendon, instead it is a transition. In fact, muscles have a core of tendinous tissue that runs all the way through them. 

Tendons transmit force from the muscle to bone but also have mechanical force of their own, acting like springs.

Now, what do we know about tendon injuries? Well…here’s the basics. 

1.       Tendons have much fewer blood vessels than other tissues and this is part of the reason that their healing process is unique. In general, Tendons heal slowly with scar tissue and not well. Repair tissue will simply not ever be as strong as the original tissue…yes that is pretty depressing, but remember that tendons are very strong and so even 80% is going to allow you to have good functionality.   

2.      Tendons require mechanical load to heal correctly and retain strength. Tendon tissue healed with progressive loading is stronger, better aligned, more normal. Immobilization for too long causes slower healing, mechanical load too soon can give poorer outcomes in healing too. Controlled progressive mechanical load increases are thought to be ideal. Bottom line is: you MUST give your healing tendons some stress during the healing process, but not so much that you’re re-injuring yourself. In fact, even healthy tendons will actually degenerate if they are not subjected to stress. 

3.      Tendons heal in three stages,

a.      Week 1: Inflammatory response, migration of cells to site, new vessels formed. It may be best not to combat initial inflammatory response with NSAIDS. The first inflammatory response may be needed to initiate the healing process. From what I’ve read, I personally would wait at least 4 days after an acute injury before taking NSAIDS.  That being said, after a week or so (after initial inflammation period), then it might be beneficial to use NSAIDs, as some studies have shown that more long term inflammation is detrimental to the healing process.  As always, and especially with tendons, beware of NSAIDS also because they may block enough pain to allow you to further overload your injured tendons.  

b.      Week 1-4: initial disorganized collagen repair. Basically what happens here is a bunch of new blood vessels form and increased collagen production begins. Unfortunately, the collagen fibers are disorganized and random at this point and not very functional. What can we do about this? Well, the overwhelming general consensus is that you want to start adding tension and load to your tendons ASAP after an injury.  It’s generally best to begin by doing ROM exercises after the initial inflammation phase is complete in order to acclimate the tendon to loads and to give the best chance for healthier and stronger tissue. After ROM, then start progressively adding loads.  They think that early loading after injury may somehow make the new collagen fibers more organized and functional.   Generally it’s advised to lower the level of activity if pain is felt. Also, some recommend that eccentric exercise may be best for tendon injury rehab.

c.       After 4 weeks, realignment and scar tissue repair. This phase can take up to a year. Basically what happens here is that the body is trying to realign the collagen fibers and to shore up the tendon. The new blood vessels that were formed to in the beginning of the healing process will also start to recede. Phase III of the healing process can take up to a year. After 3 months tendons have typically 80% of the tensile strength of normal tissue. The three phases overlap and are a continuum of healing.

4.      Acute Tendon injuries are usually the end of a long process and are due to repetitive overloading, with some external factors that may add to the problem like equipment, form, shoes, surfaces, etc. More than likely if you have tendon issues, it’s not an overnight, isolated thing…it’s probably not just ‘tendonitis’, it’s tendinopathy, meaning that over the years you have acquired a bunch of micro-tears that haven’t been healing correctly and you have disorganized collagen fibers and extra blood vessels in the problem tendon.

*So the tl;dr is this and these studies is:*

Make sure that you’re paying attention to tendon issues early on and alter your training, form, equipment, etc to let them heal before they get too bad, because once you hurt them they are never really the same.

Many times sudden tendon injuries are actually from years of incomplete healing from overload that the athlete may have never been aware of. They're finding out that it's less about periodic inflammatory response and more about the tissue failing to heal repeatedly over time. 

If you do hurt a tendon, lay off of it but start doing rehab exercises for it as quick as you can, and progressively increase the resistance. If you feel pain, then back it off to easier/lighter exercises.

It’s most likely best to minimize using NSAIDS after an initial acute tendon injury for about 4 days. After that, you can use them, but bear in mind that they make it easier to re-injure the tendon during rehab.

Finally, tendons take a really long time to heal and the healing continues long after the pain subsides, so bear that in mind when you train.

Below are the papers I read; the second one is a book which costs like 400 dollars so I took what I could from the 20 or so pages of preview sections on a couple of different sites. 

Principles of Rehabilitation for Muscle and Tendon Injuries

Maffulli, Renstrom, Leadbetter

Tendon Injuries: Basic Science and Clinical Medicine


S. Pribut DPM, 8/28/17
The Science of Tendinopathy

Journal of Bone and Joint Surgery

The Role of Mechanical Loading in Tendon Development, Maintenance, Injury, and Repair 2013

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3748997/


Yang, Rothrauff, Tuan

Tendon and Ligament Regeneration and Repair: Clinical Relevance and Developmental Paradigm

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4041869/


Here are some brief thoughts on the role of various hormones on tendon healing and degeneration. The paper this is based on is a recent and fairly comprehensive review of studies, but any additional interpretations of this paper or knowledge in this area will be welcome.



*Hormone Influences on Tendons:*

Insulin:

Tendons in diabetics tend to have less collagen and less organized collagen fibers, a thickening of tendons, and a host of tendon cell quantity and functional abnormalities. Diabetics have a greater incidence of tendon injuries in general. I’m not terribly knowledgeable on insulin use so I’m not sure how all this may relate to exogenous insulin use as a PED.

Thyroid hormones:

It looks like T3 and T4 have a significant role in tendon repair and increase collagen production. People with hypothyroidism can have issues with tendons not being properly oxygenated which leads to deterioration.

Estrogen:

Estrogen deficiency can slow the tendon healing process by decreasing cell proliferation.

Androgens:

It appears as though androgens and DHT can cause some issues with tendon repair..to what extent and and at what dosages is unclear. I think the take away here is that the tendon healing process is very complicated and sensitive and AAS does seem to have some kind of effect on it.

“In vivo, anabolic androgenic steroids (AAS) in combination with jumping exercises enhance calcaneal, superficial and deep flexor tendon remodeling, even though androgen abuse may compromise tendon adaptation with an increased risk of tendon ruptures. In fact, AAS reduce insulin-like growth factor-1 (IGF-1) mRNA levels in some tendons, decreasing collagen synthesis, and compromise tendon healing.”


IGF1, GH:

Studies have shown that GH can increase collagen production and also plays a role in tendon repair, possibly by increasing IGF1 in the tendon tissue, but other studies have shown no effect on tendons from GH. In other words, it looks like it’s likely but not entirely clear that GH has a direct or indirect effect on tendon repair.

And finally, *Genetics*. Scientific knowledge on genetic the genetic factor of tendon injuries is still pretty slim. There’s been some connections made with Achilles tendon injuries and some genetic factors, so it looks like there may be some genetic predispositions with at least some tendons. It looks like this information might be useful in the future, but responsible injury prevention protocols can probably equalize things even if you have a predisposition for a certain kind of tendon injury.

Genetics is not my strong suit, but here’s a couple of good reads if that’s your cup of tea.

The Genetics of Sports Injuries and Performance

Muscle, Ligament and Tendons Journal

Maffuli, Margiotti, Longo, Loppini, Fazio, Danaro 2013

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3838326/


Schwellnus, September, Collins ‘07

Tendon and Ligament Injuries: the Genetic Component

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658952/

So this is all I got for now. I hope this helped you out, gave you some food for thought, or at least helped you sniff out some of the BS that somebody might be shoveling your way.  I welcome anybody to comment or critique on any and all of my interpretations on these papers. I did my best to find relevant and up to date information, but if I missed something feel free to add it.

Keep those tendons healthy!

M


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## ECKSRATED (Aug 29, 2017)

Nice post with some good info.


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## StillKickin (Aug 29, 2017)

Thank you Mythos.
I appreciate all the effort you put into making that post for us!


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## BigSwolePump (Aug 29, 2017)

I have been having elbow issues lately and have been looking for something like this. Thanks!


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## Beezy (Aug 29, 2017)

Son of a b... 
As depressing as "can take up to a year to heal" was to read, it explains a lot about my elbow and heal pain. 
Thanks Mythos


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## stonetag (Aug 29, 2017)

Useful stuff, thanks brother.


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## Mythos (Aug 29, 2017)

> Thank you Mythos.
> I appreciate all the effort you put into making that post for us!


Thanks! I learned a lot from this board, just wanted to give a little something back. 



> Nice post with some good info.


Thanks!



> I have been having elbow issues lately and have been looking for something like this. Thanks!



I hear you man..i was having a hard time finding any useful info on this subject. Unfortunately i didn't find any magic bullets, but now I have some good things to keep in mind now going forward.


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## Mythos (Aug 29, 2017)

Beezy said:


> Son of a b...
> As depressing as "can take up to a year to heal" was to read, it explains a lot about my elbow and heal pain.
> Thanks Mythos



I know man..i know. Not a lot of hopeful news there. I think if there's good news in all this it's that you dont need to immobilize for extended periods for them to heal, and actually it's better to start loading them little by little as soon as you can. Gives you some control in the healing process in what can feel like a hopeless situation.


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## NoQuarter (Aug 29, 2017)

Thank you, lots of info and explained a lot !!!!  Glad to know, my shoulder took about a year and a half, but, now I can pretty much do everything the same as before.  Every once in a while there is a slight reminder of the injury, at least now I know why.


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## BRICKS (Aug 29, 2017)

Thanks brother, good stuff


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## Solomc (Aug 30, 2017)

Props dude. Nice post


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## kittensandkilos (Sep 19, 2017)

This was such a good and insightful post. Thanks for spending the time making this.


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## DocDePanda187123 (Oct 16, 2017)

Moved this to the science and study section as requested and giving Mythos a well deserved bump for an excellent thread.


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## Mythos (Oct 18, 2017)

DocDePanda187123 said:


> Moved this to the science and study section as requested and giving Mythos a well deserved bump for an excellent thread.



Thanks Doc, much appreciated!


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## Send0 (Nov 6, 2021)

This is a good primer / read on tendons. I thought I'd give this a well deserved bump.


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## Clyde (Apr 28, 2022)

My personal experience with tendon injury. 

Back in the 1990's working out, I _believe_ injured both my distal biceps tendons over time. Never officially diagnosed or even went to a doctor. I permanently eliminated all isolated biceps work at a point, because I simply couldn't work them, due to the tendon pain. Continued working out for years after the injury, learning how to not engage my biceps in compound movements. IE: wide grip pullups, bent rows, dead lifts, etc without much pain

I pretty much was done with the whole working out and gear by the early 2000's. I never got over the biceps tendon pain whenever I put a heavy load on them though. Pretty much learned to work, live around the issue.

Now fast forward to around 2014. While working, I was moving a framework of large welded steel with a forklift. Probably around 1000lbs total, but pretty large and spread out. While making a manual adjustment for location on the forks, I ended up pulling with a jerking motion, using my body weight with my arms nearly fully extended. I ended up tearing my right distal biceps tendon from the bone. It was obvious with a loud snap that I also felt.

Got into surgery within a week to reattach it. The doc drilled a hole through one of the forearm bones, pulling the tendon through and using some kind of hardware to keep it anchored while the bone and tissue regrew around it.  It's back to good as new and pain free now. Now so for the left arm though, still painful if I overload it.

TLDR: In my case, I don't think my biceps tendons ever properly healed, even after 10+ years. 
Without an actual medical diagnosis though, this is all just anecdotal from my perspective. I'm also not sure what was causing the actual pain. A partial tear that never healed possibly?


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## Stickler (May 13, 2022)

Mythos said:


> ,


I appreciate the article. Broken down and an easy read.


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## wotmeworry (May 13, 2022)

Thanks Mythos, a handy review.
The challenge I have found is getting the amount of stress on the recovering tendon right.  Going by pain level (ie almost none) has led me to do too much, too soon.  Actually, the real challenge is getting my workouts right so that I avoid tendon overuse injuries in the first place.


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## Stickler (May 13, 2022)

wotmeworry said:


> Thanks Mythos, a handy review.
> The challenge I have found is getting the amount of stress on the recovering tendon right.  Going by pain level (ie almost none) has led me to do too much, too soon.  Actually, the real challenge is getting my workouts right so that I avoid tendon overuse injuries in the first place.


I've found myself changing movements and usually requires me to use more cables than free weights. I can't figure out low level exercises that aren't higher than 10lbs on certain movements. Very disheartening


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## wotmeworry (May 13, 2022)

Stickler said:


> I've found myself changing movements and usually requires me to use more cables than free weights. I can't figure out low level exercises that aren't higher than 10lbs on certain movements. Very disheartening


Low-level as in low stress on a recovering tendon?  There are likely several ways to get a low-stress load for movements.

For my elbow extensor I started with pretty much an isometric load - very limited movement, then added range and load over time (presses against a wall, progressively stepping back and making it harder from almost nothing to almost push-up).  Still not right, but I have to be patient.


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