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The maximum shortening velocity of muscle should be scaled with activation
Journal article   Open access   Peer reviewed

The maximum shortening velocity of muscle should be scaled with activation

John W. Chow and Warren G. Darling
Journal of applied physiology (1985), Vol.86(3), pp.1025-1031
03/01/1999
DOI: 10.1152/jappl.1999.86.3.1025
PMID: 10066719
url
https://doi.org/10.1152/jappl.1999.86.3.1025View
Published (Version of record) Open Access

Abstract

The purpose of this study was to determine whether the maximum shortening velocity ( V max) in Hill’s mechanical model (A. V. Hill. Proc. R. Soc. London Ser. B. 126: 136–195, 1938) should be scaled with activation, measured as a fraction of the maximum isometric force (Fmax). By using the quick-release method, force-velocity (F-V) relationships of the wrist flexors were gathered at five different activation levels (20–100% of maximum at intervals of 20%) from four subjects. The F-V data at different activation levels can be fitted remarkably well with Hill’s characteristic equation. In general, the shortening velocity decreases with activation. With the assumption of nonlinear relationships between Hill constants and activation level, a scaled V max model was developed. When the F-V curves for submaximal activation were forced to converge at the V max obtained with maximum activation (constant V max model), there were drastic changes in the shape of the curves. The differences in V max values generated by the scaled and constant V max models were statistically significant. These results suggest that, when a Hill-type model is used in musculoskeletal modeling, the V max should be scaled with activation.

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