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| Influence of stretch-shortening
cycle on mechanical behaviour of triceps surae during hopping.
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Belli A, Bosco C.
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| 1992 |
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| NCBI |
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Laboratory de Physiologie, Universites de Saint Etienne et de Lyon
Sud, France.
Six subjects performed a first series of vertical plantar flexions
and a second series of vertical rebounds, both involving muscle triceps
surae exclusively. Vertical displacements, vertical forces and ankle
angles were recorded during the entire work period of 60 seconds per
series. In addition, expired gases were collected during the test
and recovery for determination of the energy expenditure. Triceps
surae was mechanically modelled with a contractile component and with
an elastic component. Mechanical behaviour and work of the different
muscle components were determined in both series. The net muscular
efficiency calculated from the work performed by the centre of gravity
was 17.5 +/- 3.0% (mean +/- SD) in plantar flexions and 29.9 +/- 4.8%
in vertical rebounds. The net muscle efficiency calculated from the
work performed by the contractile component was 17.4 +/- 2.9% in plantar
flexions and 16.1 +/- 1.4% in vertical rebounds. These results suggest
that the muscular efficiency differences do not reflect muscle contractile
component efficiency but essentially the storage and recoil of elastic
energy. This is supported by the relationship (P less than 0.01) found
in vertical rebounds between the extra work and the elastic component
work. A detailed observation of the mechanical behaviour of muscle
mechanical components showed that the strategy to maximize the elastic
work depends also on the force-velocity characteristics of the movement
and that the eccentric-concentric work of the contractile component
does not always correspond respectively to the ankle extension-flexion.
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