The force generated by a muscle depends on many
factors including the degree of activation by the nervous
system, its architecture (including the angle at which
muscle fibers insert into the tendon known as pennation
angle), the muscle size, the space between myofilaments,
the number of actin–myosin cross-bridges formed, the
force generated by each cross-bridge, and the quality of the
interaction between the cellular elements (see above). With
regards to the latter, researchers in the field have realized
that the correlation between muscle strength and size is not
unity suggesting that other factors contribute to force
production. The force generated by a muscle adjusted for
its size is known as specific force and has been accepted as
an indicator of muscle quality. It is known that this property
is reduced in older humans (see below) and with
denervation.