I was wondering if anyone knew why the terms eccentric and concentric were chosen to refer to lengthening and shortening muscle contractions?

The basic etymology of the words are to do with alignment with the centre of something. Eccentric is derived from the Greek for "off centre" and is also commonly used in bio-mechanics, another branch of sports science, to refer to a force applied out of alignment with an object's centre of gravity. I couldn't see how this definition applied to a lengthening muscle contraction, and haven't been able to find any information on why the terms were chosen.

I'd appreciate any help.

  • $\begingroup$ Try a Google search for a video demonstrating sarcomere contraction. $\endgroup$ Jan 5, 2019 at 13:00
  • $\begingroup$ Are you suggesting it's just to do with the direction the z-lines are moving relative to the m-lines? ie. eccentric would mean 'away from centre' as in away from the m-line, therefore lengthening? $\endgroup$
    – strava
    Jan 6, 2019 at 14:25


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