.....at : https://www.researchgate.net/figure/The-inverted-pendulum-and-spring-loaded-inverted-pendulum-models-One-template-for_fig1_328134715 (https://www.researchgate.net/figure/The-inverted-pendulum-and-spring-loaded-inverted-pendulum-models-One-template-for_fig1_328134715)
You can read here :..."a spring loaded inverted pendulum..is ABSORBING energy during landing and RELEASING it during take-off"...it works as a "muscle"(contraction-expansion).
Thinking alike, but as in a "mirror" for a free falling elastic pendulum...we can play a "self" rotating kiiking toy?! (See the topic with this title...)
Al_ex