Was uns der Trizeps von Ratten über science-based Training lehrt

What rats' triceps teaches us about science-based training

Some time ago I myself  Clicked around the Physiopedia website a bit as part of a post-lunch search to see if I could find anything interesting about anatomy.

Eventually I landed on their side above the triceps brachii (1).

Under "Function" I read the following paragraph:

"Muscle histology and mean innervation ratios estimated from the absolute number of motor neurons (MN) showed that the medial head was composed predominantly of small type I fibers and motor units (69 fibers/MN). In contrast, the lateral fascicle contained a large amount of large type IIb fibers and motor units (179 fibers/MN), while the long head consisted of a more balanced mix of fiber types and motor units (99 fibers/MN). Therefore, the lateral head is used for movements that occasionally require high force, while the medial head allows for more precise, low-force movements.” (2)

I was surprised because this is contrary to what I see and analyze all the time in the field, in the gym and in the training programs of the clients and athletes I work with.

In practice, statistically, the farther the elbow is off the ground in a standing position, the greater the recruitment of the fast-twitch fibers. Statistically, the long head of the triceps is the most nearly-twitch dominant head of the three heads of the triceps.

My questions were: How did the study come to this conclusion and the results?

I looked at the abstract and found one word that really surprised me. It was the word "rat".

A closer look at the full-text PDF of the study revealed the whole thing. 

The study group were bred albino laboratory rats.

Yes, there are definitely many benefits to doing research with rats. 

But researching muscle histology, muscle innervation, and potential fiber recruitment with an animal that walks on all fours, and then drawing conclusions and making recommendations for humans walking upright on two feet based on those results, seriously?

And I even stumbled across the same reference on the triceps brachii wikipeda page (3).

There are three key points to consider in this scenario:

1. Basically, no one looks at every link in an article in detail, including me.

2. I took a closer look at the reference in this case only because the conclusion contradicted what I observe in practice.

3. Using this conclusion in the program design and exercise selection given on the website would have resulted in a suboptimal training program. And thus to a lack of progress in training.

This is a classic example of how the use of science, or the interpretation of science, is sometimes significantly inferior to the use of real-world observations. 

Not because the science is unimportant or inferior. 

But because their application in this scenario is. 

Inferring muscle fiber recruitment from a rat walking on all fours to a human walking upright on two feet is simply wrong.

This is similar to inferring the nutrition of humans from the diet of a gorilla or an ox.

Use science to optimize training planning by combining it with good real-world observations.

For more progress through training.


  1. https://www.physio-pedia.com/Triceps_brachii
  2. Lucas‐Osma AM, Collazos‐Castro JE. Compartmentalization in the triceps brachii motoneuron nucleus and its relation to muscle architecture. Journal of Comparative Neurology. 2009 Sep 20;516(3):226-39.
  3. https://en.wikipedia.org/wiki/Triceps
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