Changes

:::::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.

=='''Muscle metabolism'''==  

=='''Muscle metabolism'''==  

==='''Endurance depends on muscle use'''===   

==='''Endurance depends on muscle use'''===   

A characteristic of animals reared without normal muscle usage, for example pigs and broiler chickens, is an abundance of muscle fibres with low aerobic capacity and associated pigment.  In domestic pigs the deep red part of M. semimembranosus, for example, contains a high proportion of aerobic fibres that are used for posture and quiet propulsion even in a closely confined animal.  In contrast with the superficial fibres that are all too seldom used for propulsion, and are very pale.  A similar comparison can be made with the red leg muscles and pale wing muscles of broiler chickens.  Yet another example is the endurance of a hare that with its red musculature can lead a pack of hounds for an hour, and a rabbit that, with a sudden burst of energy, finds a burrow and time to repay the oxygen debt of its pale musculature.  Athletic ability and its improvement by training are also related to an improved aerobic capacity of muscles along with an accompanying cardiovascular fitness.  

A characteristic of animals reared without normal muscle usage, for example pigs and broiler chickens, is an abundance of muscle fibres with low aerobic capacity and associated pigment.  In domestic pigs the deep red part of M. semimembranosus, for example, contains a high proportion of aerobic fibres that are used for posture and quiet propulsion even in a closely confined animal.  In contrast with the superficial fibres that are all too seldom used for propulsion, and are very pale.  A similar comparison can be made with the red leg muscles and pale wing muscles of broiler chickens.  Yet another example is the endurance of a hare that with its red musculature can lead a pack of hounds for an hour, and a rabbit that, with a sudden burst of energy, finds a burrow and time to repay the oxygen debt of its pale musculature.  Athletic ability and its improvement by training are also related to an improved aerobic capacity of muscles along with an accompanying cardiovascular fitness.

 

=='''Scaling effects on quadrupedal design'''==  

=='''Scaling effects on quadrupedal design'''==