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Influence of stretch magnitude on the stretch-shortening cycle in skinned fibres
Author(s) -
Atsuki Fukutani,
Walter Herzog
Publication year - 2019
Publication title -
journal of experimental biology
Language(s) - English
Resource type - Journals
eISSN - 1477-9145
pISSN - 0022-0949
DOI - 10.1242/jeb.206557
Subject(s) - sarcomere , stretch shortening cycle , contraction (grammar) , chemistry , anatomy , work (physics) , magnitude (astronomy) , materials science , biophysics , physics , medicine , biology , myocyte , thermodynamics , jump , quantum mechanics , astronomy
The mechanical work attained during shortening is increased by prior stretching. Recently, we suggested that the residual force enhancement (RFE) may contribute to this enhanced work. RFE can be changed reliably by changing the stretch magnitude. Therefore, the purpose of this study was to examine the effect of stretch magnitude, and by association of RFE, on the mechanics of the stretch-shortening cycle in skinned skeletal muscle fibres. Three tests were performed using skinned rabbit soleus fibres (N=18). The first test was a pure shortening contraction in which fibers were activated and then shortened from an average sarcomere length of 3.3 to 3.0 µm. The second test was a SSC in which fibers were activated and stretched from 3.0 µm to 3.3 µm, and then shortened to 3.0 µm. The third test was a SSC in which fibers were activated and stretched from 2.4 to 3.3, and then shortened to 3.0 µm. The mechanical work during shortening and the force maintained 15 s after the end of shortening were determined. The relative increase in mechanical work with respect to the pure shortening condition, was greater for the large than the small stretch condition (p<0.001). Similarly, the relative increase in force 15 s after the end of shortening was greater for the large than the small stretch condition (p=0.043). We conclude that increasing the magnitude of stretch results in an increase in mechanical work and increased force at steady-state following the stretch, likely because of the greater RFE.

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