Research on tendon strength increase

Hi all,

I was wondering if anyone has any links to research into the time it takes for tendon strength to increase as a result of exercise. I've always heard that this takes a long time, and people talk about the really long periods of training required before your tendons get any stronger so that your muscles end up overpowering your tendons which leads to injuries. I'm keen to read the research on this but haven't had much joy...

Thanks for any help you can offer!

Stephen

I think that the Rock Climber's Training Manual, by the Anderson brothers, says it takes up to 6 years or so. I'm not sure whether there are faster times for some people, though.

Yeah, that's the kind of figure I've seen - I'm wondering where they get that from, though. Is everyone just repeating what someone else said? Is there research to support this, or is it just something someone made up that's now become accepted wisdom in climber circles?

I'm curious because if the six year figure is right, how on earth can body builders or weight lifters survive? Surely they must blow up every tendon in their body doing their workouts.

Here's one: ncbi.nlm.nih.gov/pubmed/199…

The money quote: "Muscle CSA [cross-sectional areas] and tendon stiffness did not change until 2 months of training period, and afterward, the increases in muscle CSA and tendon stiffness reached statistical significance at the end of training period [3 months] (both p's < 0.05)."

Nice find! Also "the adaptations of tendon properties and muscle morphology to resistance training are slower than those of muscle function", which agrees with what we've been told, though this paper at least suggests that tendons do get stronger within a couple of months. Which makes sense, surely, as it'do have to be hugely disadvantageous for it to happen far slower than muscle strength increases...

I don't have literature sources, but will just add my own anecdotal evidence: After becoming comfortable with the marathon distance pain free, I started training for ultradistance trail running races in 2000, and it took about 6 years for my achilles tendon, and peroneal tendon to "adjust" and become problem free. I was focussed on the slower, steeper, courses and it was the really steep hill work, and steep inclined treadmill work, that was stressing these tendons.
In a different period of years, my wife did exactly the same thing, and her tendons took about the same amount of time to adjust. She had more trouble with achilles, and a bit less with the peroneal.
BTW, the peroneal tendon runs behind the ankle bone on the outside of your ankle. On super steep hills, it gets stressed, esp. if you turn your ankle to the outside.
Climbers are obviously more concerned with elbow and hand tendons, but I'd guess the time period for healing and strengthening would be similar.

Stephen Minchin wrote:Nice find! Also "the adaptations of tendon properties and muscle morphology to resistance training are slower than those of muscle function", which agrees with what we've been told

Whoa ...
Read the whole abstract carefully.
"Muscle morphology" refers to Cross-Sectional Area of muscle. This is what lots of people call "HYPertrophy".

So the quoted conclusion means really:
Muscle HYPertrophy and Tendon stiffness increase with training time at about the same rate.

Which is not what the old climbing lore (ever-repeated) says.

isometric --
anyway the article is about isometric training. Which has long been known not to be very effective for muscular HYPertrophy. So I guess in addition to confirming that, this article is also saying isometric is not so good for tendon growth either.

I guess that's why the majority of modern English-language climbing-training books emphasize dynamic methods for training finger-muscle HYPertrophy.

also ...
Climbers need to be careful to distinguish between "normal" tendons: one at each end of each voluntary muscle, to connect the muscle to bones and joints. Versus other tendon-like connectors like say finger pulleys and "climbers elbow" tandons.
And be cautious about applying findings about "normal" tendons to the other kind.

What makes the two type of tendons different?

why is a finger pulley different in it's strength adaptation than any other tendon?

I would suggest considering doing your own searches in Pubmed or Google Scholar to find what you're looking for. The ability to interpret the material properly is a whole other ballgame, though.

I have liked and used this book in the past: Human Tendons: Anatomy, Physiology and Pathology by Laszlo Jozsa.

To be concise, a lot of the "knowledge" bandied about regarding tendon adaptation to strength training (which includes climbing, yes) are based on research which pre-dates current improved methods of studying tendon remodeling and behavior in vivo. Using new methods of ultrasonography, among others, I have seen studies which find that some tendons can remodel very fast and within similar timeframes as muscles. For instance:

"Also, new experimental evidence shows that, contrary to earlier beliefs, the metabolic activity in human tendon is remarkably high and this affords the tendon the ability to adapt to changing demands." ("Human tendon behaviour and adaptation, in vivo" by Magnusson et al)

SteveMarshall wrote:What makes the two type of tendons different? why is a finger pulley different in it's strength adaptation than any other tendon?

Finger pulleys aren't tendons. They are annular ligaments. Also, I am confused by what kenr said regarding "climber's elbow tendons" being somehow not normal tendons.... they are.

That said, tendon morphologies and function vary widely depending on the muscle they are attached to. Tendon "performance" isn't uniform and their ability to withstand tensile and shear stresses aren't all the same. So studying one doesn't imply you understand all others.

kenr wrote:isometric -- anyway the article is about isometric training. Which has long been known not to be very effective for muscular HYPertrophy. So I guess in addition to confirming that, this article is also saying isometric is not so good for tendon growth either.

First, (off topic) but isometric contractions have been shown to induce hypertrophy. One study does not provide a conclusion on the entire scope of isometric exercise (they only used 70% of max, for instance). Also cross-sectional area of muscle and tendon isn't necessarily indicative of increases in function (which the study did support).

Thank you for this, Aerili - awesome to hear more from someone who I'm confident knows what they're talking about. I was also interested in your point that cross-sectional area of muscle and tendon isn't necessarily indicative of increases in function, as I'd thought that for muscle at least that was directly correlated. Unfortunately I'm both skinny and weak, but oh well...

Thanks so much Aerili, for taking the time to carefully communicate all this good stuff you know about tendons and muscles.

Aerili wrote:I am confused by what kenr said regarding "climber's elbow tendons" being somehow not normal tendons.... they are.

I don't know as much as you, so I was just wrong.
I made an inference from something I had heard about climber / golfer's elbow injuries + rehab. But some inferences are wrong (and why this one was wrong would make a separate discussion topic).

Ken

Stephen Minchin wrote:I was also interested in your point that cross-sectional area of muscle and tendon isn't necessarily indicative of increases in function, as I'd thought that for muscle at least that was directly correlated. Unfortunately I'm both skinny and weak, but oh well...

Muscle CSA is correlated with force output. You are not wrong. But it is not 1:1. There are other factors, like neural drive and organization, which contribute a large percentage to a muscle's ability to generate force.

As for tendons, they can become stiffer without increases in CSA. Thus, function changes without muscle or tendon hypertrophy.

Aerili wrote: Muscle CSA is correlated with force output. You are not wrong. But it is not 1:1. There are other factors, like neural drive and organization, which contribute a large percentage to a muscle's ability to generate force. ...

i call this 'freak factor', which of all the anomalies i have, unfortunately this isn't one of them :(