The amount of force generated also depends on several
basic biomechanical properties of the musculoskeletal
system. For example, force depends on the length of the
muscle or sarcomere (directly related to the position of
the limb) upon activation. This property is known as the
force–length relationship. At lengths longer and shorter
than the optimal length, the force generated after activation
is lower because the overlap between actin and
myosin needed for cross-bridge formation is sub-optimal.
From a practical point of view, this means that the performance
of daily activities is dependent on the angular
position of the joint; in other words, carrying heavy
objects with the upper limbs is usually done with the
elbows at 90 of flexion because it optimizes actin–
myosin overlap.