, Volume 336, Issue 4, pp 277-288

Elasticity as an expression of cross-bridge activity in rat muscle

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Summary

  1. Rat soleus muscles (SOL) were isolated and the force-shortening curves were determined during isometric maximal tetani. These were measured by applying sudden shortenings of different magnitudes to one end of the muscle while recording the resulting drop in tension.

  2. From the force-shortening curve a stiffness-force curve was derived. Then a stiffness-force curve was measured by applying small shortenings (20 μm) to the muscle when at different lower stimulation frequencies it was exerting less than maximal tetanic force.

  3. It appeared that the two curves, taken from the same preparations, differed consistently. It was therefore concluded that muscle stiffness at a certain force depends on the way by which this force was reached. This conclusion is shown to fit very well to a sliding filaments model like the one Huxley proposed in 1957.

  4. The sudden shortenings applied to the muscle gave rise to a travelling wave in the muscle. The resulting tension transients could be explained by assuming that muscle behaves as an homogeneous body with distributed mass, stiffness and damping.