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Quadrupedal Mechanics - Anatomy & Physiology (view source)
Revision as of 22:18, 28 November 2013
, 22:18, 28 November 2013→A severe restriction on muscle function: active insufficiency
==='''A severe restriction on muscle function: active insufficiency'''===
==='''A severe restriction on muscle function: active insufficiency'''===
[[File:QMFig 8.9.png|thumb|'''Fig 8.9 The contribution of a longheaded muscle to the standing jump of the cat''']]
There is a problem associated with shortheaded muscles that is fundamental to the design of limbs. For any muscle, there is only one stage at which the force is maximal over the whole range over which the muscle contracts (Fig. 4.4). A shortheaded muscle is therefore properly effective at only one angle of the joint over which it acts. A muscle is therefore insufficient because of the way its contractile mechanism works. A muscle with its sarcomeres at any length other than near 2.2 µm is said to be actively insufficient.
There is a problem associated with shortheaded muscles that is fundamental to the design of limbs. For any muscle, there is only one stage at which the force is maximal over the whole range over which the muscle contracts (Fig. 4.4). A shortheaded muscle is therefore properly effective at only one angle of the joint over which it acts. A muscle is therefore insufficient because of the way its contractile mechanism works. A muscle with its sarcomeres at any length other than near 2.2 µm is said to be actively insufficient.
:::::'''Fig 8.9 The contribution of a longheaded muscle to the standing jump of the cat'''
:::::'''Fig 8.9 The contribution of a longheaded muscle to the standing jump of the cat'''
:::::The semitendinosus muscle (dashed outline) has the same length when the hindlimb is in the fully flexed position as it does with the limb in the fully extended position. This muscle therefore assists hip extension without changing from its optimal length. It is able to do this only by the counteractive action of stifle extensors.
:::::The semitendinosus muscle (dashed outline) has the same length when the hindlimb is in the fully flexed position as it does with the limb in the fully extended position. This muscle therefore assists hip extension without changing from its optimal length. It is able to do this only by the counteractive action of stifle extensors.