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A few thoughts following up on the post about Steve Magness’s muscle tension article in Running Times. Steve was kind enough to send me a copy of Marius Bakken‘s medical school thesis, which consisted of two documents: a detailed literature review on efforts to characterize and measure muscle tension, and a clinical trial investigating whether regular cross-friction massage can reduce muscle tension. It’s still a very young field of study, but it turns out there is some literature devoted to the ideas discussed in Steve’s article.
What Steve is talking about here is what you might call “passive” muscle tension — the tension that remains in your muscles even when they’re completely relaxed (i.e. receiving no neural instructions to contract). Bakken adopts the definition of “resting muscle tone” from a 1998 journal paper, which is:
the elastic and/or the viscoelastic stiffness in the absence of contractile activity.
So how do you measure this tension? Most simply, you relax your muscle and press into it to see how stiff it is. This is, obviously, a pretty crude measurement. Bakken is now using a tool developed by an Estonian company called Myoton (shown above), which measures the frequency and damping of muscle oscillations to determine muscle tone, elasticity and stiffness. That’s the tool he used for his massage study, in which five athletes received 20 minutes of massage once a week for four weeks. The Myoton showed that their resting muscle tone decreased by an average of 3.3%, and EMG measurements of nerve signals showed that the decrease was unrelated to changes in active muscle contraction.
If you poke through the references in Bakken’s literature search, you find various interesting hints — e.g. links between overtraining and muscle tension in cross-country skiers in a 2002 study. There are still some pretty big pieces missing from the puzzle, for example showing a link between resting muscle tone and performance. And the mechanisms responsible for this resting tone are still being debated (is it extracellular water pressure? cross-bridges between contractile proteins?). But the documents made for an interesting read, and show that there is some serious science behind these ideas. I’ll be following further developments in this field with interest.