Spring as a muscle...

[iacob alex]

.....or muscles as a spring , at :
https://www2.nau.edu/~sll/springs.htm
If we mount a spring on a (constant length arm ) pendulum , we have :
https://youtu.be/z6_NRNw88Jw
.....a variable length arm pendulum.
If we mount a spring an a double pendulum...a.s.o.
https://youtu.be/DVr7KnpDAOc
https://youtu.be/PIWbW2co5mY
.....can we play a possible "vivid " attachment/"help" of rotational inertia ?
Al_ex