Changes

:::::'''Fig 5.1 The effect of the strength of muscles in series and in parallel'''

:::::'''Fig 5.1 The effect of the strength of muscles in series and in parallel'''

:::::A muscle contracts a distance d and lifts a weight W against gravity (a).  When two such muscles are in series, the distance lifted is 2d (b). Each muscle is effectively loaded as in (a). When the muscles are in parallel, as in (c), the load is shared and the muscles can lift twice the weight 2W through their contraction distance d.  Note that the work done (2d x W, or d x 2W) in lifting the weight by pairs of muscles is the same regardless of their configuration.  Similarly the work done by a muscle depends on the number of contractile units (sarcomeres) within it, and not on the geometrical arrangement.

:::::A muscle contracts a distance d and lifts a weight W against gravity (a).  When two such muscles are in series, the distance lifted is 2d (b). Each muscle is effectively loaded as in (a). When the muscles are in parallel, as in (c), the load is shared and the muscles can lift twice the weight 2W through their contraction distance d.  Note that the work done (2d x W, or d x 2W) in lifting the weight by pairs of muscles is the same regardless of their configuration.  Similarly the work done by a muscle depends on the number of contractile units (sarcomeres) within it (hence its weight), and not on the geometrical arrangement of the contractile units (or, in the arrangement shown in the diagrams, its shape).

 

==='''Movement strength and work'''===

==='''Movement strength and work'''===