I founde some textbooks stating that typical skeletal muscles can shorten up to 70% (optimally up to 30%) during contraction. However, I would like to look at muscles per region.
This might seem like a very unrealistically simple question, as there are many factors which determine the shortening of muscles during contraction, but I would like to create general reference values for modelling purposes.
Any advice on where to look or how to even measure this would be great!
Hello Anya,
I assume that your modelling demands data for muscle in the context of a living human, not in vitro. I'd have three remarks that might hopefully help in your research: (1) maximum shortening through contraction is limited by skeletal mobility of the joints relevant for a muscle and (2) in a real movement, especially in sport, athletes perform using the stretch reflex, i.e. muscles will shorten from a stretched configuration; that asks the question of your frame reference: what is the long and what the short between which you calculate shortening.
A sub-remark to (1): across the section of a muscle, the degree of stretch might vary, due to geometry. A sub-remark to (2): in a specific movement, the skeleton describes one trajectory, which determines the degree of stretching and shortening across all muscles involved.
Besides, wherever speed is the goal, using the time of the stretch phase to build up tension is the only way to have the contraction deliver maximum momentum at high speed, i.e. in a short time frame.
I do of course understand that time and technical constraints might limit your modelling effort to a very simplified level. How you simplify will determine the value of your model; That's why I answer here. Remember Einstein: "do it as simple as possible, but not simpler".
As an engineer with a math/physics background and a student of complex systems, I've spent 40 years coaching javelin throwers and trying to understand that complex movement, at the fringe of control. That led me to design a technical model that works and is quite different from the mostly picture-based "analysis" handed down through generations of coaches. Here you can observe another "interesting" aspect of movement and muscles working: most athletes (even at world class level) bring their skeleton into a configuration where joints jam before the muscles can reach a high degree of stretch (especially visible in the shoulder). That leads to consistently frustrating performance and damage in the joints as a reward, not a nice combination.
Hi Francis, Thank you for the response. I came to a similar conclusion based on my anatomical background and prior investigation over the past month into the matter. I am glad that you were able to confirm this for me. Would you be able to provide some research material (any publications etc) of your mentioned model? Best of luck for your future research.
Hi Anya,
I haven't published anything on the subject, as I didn't find the time yet to write it up. I plan to do some writing next year, when I'll have more time. I might also do some work with a technology university near Frankfurt, Germany, where I live.
Also, I don't know of any published material that takes a similar approach to mine. Most scientific literature I have seen is written in a rather detailed perspective. So far I haven't seen anything written from a holistic, systemic perspective on human movement. Specific sports literature on complex movements rarely ventures beyond established practice. Feels a bit like a "Thomas Kuhn" situation (if you haven't read his "Structure of Scientific Revolutions", I recommend it warmly!)
I feel that there is a desert here, and that the advent of much more powerful computing could help build models and simulation tools of whole body movement with underlying real anatomy, down to muscle substructures and the nervous system, rather than oversimplified "stick insect" models. With "game engines", the technology underlying video games, we might have a platform on which to build.
Such a tool could find many applications, also beyond sports (e.g. design of ortheses and prostheses). A business idea could be to offer technical advice / coaching services for safer / less harmful and more effective movement to athletes, based on uploading video and some data on their body.
What do you think of that?
Kind regards,
Francis
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