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Muscle contraction history: modified Hill versus an exponential decay model (2000)

Ettema, Gertjan J. C. ; Meijer, Kenneth

Springer

Biological cybernetics 83 (2000), S. 491-500

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ISSN: 1432-0770

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Computer Science , Physics

Notes: Abstract. In recent years, it has been recognised that improvements to classic models of muscle mechanical behaviour are often necessary for properly modelling co-ordinated multi-joint actions. In this respect, the purpose of the present study was to improve on modelling stretch-induced force enhancement and shortening-induced force depression of muscle contraction. For this purpose, two models were used: a modified Hill model and a model based loosely on mechano-chemistry of the cross-bridge cycle (exponential decay model). The models were compared with a classic Hill model and experimental data. Parameter values were based, as much as possible, on experimental findings in the literature, and tested with new experiments on the gastrocnemius of the rat. Both models describe many features of slow-ramp movements well during short contractions (300–500 ms), but long-duration behaviour is described only partly. The exponential decay model does not incorporate a force–velocity curve. Therefore, its good performance indicates that the status of the classic force–velocity characteristic may have to be reconsidered. Like movement-induced force depression and enhancement, it seems a particular manifestation of time-dependent force behaviour of muscle, rather than a fundamental property of muscle (like the length–tension curve). It is argued that a combination of the exponential decay model (or other models based on the mechano-chemistry of contraction) and structurally based models may be fruitful in explaining this time-dependent contraction behaviour. Furthermore, not in the least because of its relative simplicity, the exponential decay model may prove more suitable for modelling multi-joint movements than the Hill model.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004220000190

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Effects of distribution of muscle fiber length on active length-force characteristics of rat gastrocnemius medialis (1994)

Ettema, Gertjan J. C. ; Huijing, Peter A.

New York, NY [u.a.] : Wiley-Blackwell

The @Anatomical Record 239 (1994), S. 414-420

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ISSN: 0003-276X

Keywords: Rat ; Skeletal muscle ; Length-force curve ; Gastrocnemius ; Modelling ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine

Notes: Background: The length-force curve of mammalian skeletal muscle is often wider than expected on basis of the optimum length of the muscle fibers. Two important effects may explain this discrepancy: muscle pennation and distribution of fiber lengths in the muscle. In the present study of the effects of a Gaussian distribution of fiber lengths on muscle length-force characteristics were investigated in rat gastrocnemius medialis.Methods: Fiber length-force characteristics and parameter values of the Gaussian distribution were derived from literature data (Stephenson et al., 1989, J. Physiol., 410:351-366; Heslinga and Huijing, 1990, J. Morph. 206:119-132; Zuurbier and Huijing, 1993, J. Morphol., 218:167-180). Three different constructions of the distribution model were compared with experimental data. Pennation effects were incorporated in the model.Results: Two constructions gave reasonably good results: (1) the model with a fiber optimum distribution, in which fibers acted at the same absolute length at a given muscle length; (2) the model in which fiber optimum length was uniform but absolute length at a given muscle length was distributed.Conclusions: In rat gastrocnemius medialis, the magnitude of the effects of these distributions is similar to pennation effects. The current results help to explain the relative wide working range of skeletal muscles in human movement and the differences in specific muscle tension as affected by muscle type, species, and age. © 1994 Wiley-Liss, Inc.

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