Swammerdam (17th century) stimulated a muscle in a fluid-filled jar with a small-bore tube attached, measuring a slight decrease in volume, disproving the "balloonist" theory of muscle contraction. This finding is well-replicated in frog sartorius, but there is a recent claim (Clark & Demer 2016) that human eye muscles are different in that they increase as much as 18% in total volume when they contract to rotate the eye. I don't believe it!
Can anyone point me to contraction-volume measurements in vertebrate muscles, or any muscles that might be more like human EOMs, or to an expert who might know about this stuff?
Hello Joel;
I share your skepticism. The authors don't claim changing blood volume during a contraction and so they are left with some geometric change in the myotomes. They don't suggest a mechanism.
I, like you, await an informed commentator or the results of the next experiment.
Regards, Jim Des Lauriers
Could it be that muscles have auxetic properties as found in tendons,( [1] Gatt R, Vella Wood M, Gatt A, Zarb F, Formosa C, Azzopardi KM, et al. Negative Poisson’s ratios in tendons: An unexpected mechanical response. Acta Biomater 2015;24:201–8. doi:10.1016/j.actbio.2015.06.018.)? A muscle is a "tendon" with myofibrils embedded within it.
Re Stephen M Levin: Wouldn't an auxetic muscle decrease in volume when it shortens? In any case, it's actual measurements I'm after. Thanks for your interest.
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