Changes

Note that the decreased range of movement of a pennate muscle can be compensated for by an appropriate change in its skeletal attachments.  (Fig. 5.5); a strong pennate muscle, such as the deep gluteal muscle, can still deliver an effective propulsive force at the foot even though its force is directed close to the pivot at the hip.

Note that the decreased range of movement of a pennate muscle can be compensated for by an appropriate change in its skeletal attachments.  (Fig. 5.5); a strong pennate muscle, such as the deep gluteal muscle, can still deliver an effective propulsive force at the foot even though its force is directed close to the pivot at the hip.

:::::'''Fig 5.9 Contraction of a pennate muscle'''

 

:::::'''Fig 5.9 Contraction of a pennate muscle'''

:::::A fibre maintains a constant volume during contraction.  Its areas of attachment to the tendons of origin and insertion are also constant.  This figure shows a single muscle fibre with solid outlines in only two dimensions, stretched in (a) and contracted in (b). The following argument is, however, correct for a three dimensional structure.  Because the area of the parallelogram shaped fibre is constant, its length of attachment x is constant, and its area is x. y, y = y'.  Therefore although the individual fibres of the muscle increase in thickness during contraction, the pennate muscle as a whole does not.

:::::A fibre maintains a constant volume during contraction.  Its areas of attachment to the tendons of origin and insertion are also constant.  This figure shows a single muscle fibre with solid outlines in only two dimensions, stretched in (a) and contracted in (b). The following argument is, however, correct for a three dimensional structure.  Because the area of the parallelogram shaped fibre is constant, its length of attachment x is constant, and its area is x. y, y = y'.  Therefore although the individual fibres of the muscle increase in thickness during contraction, the pennate muscle as a whole does not.