What structural features of the limbs allow a flea to jump long distances?

The flea lives in the fur of animals, is a parasite that sucks the blood of the host. It can be a carrier of especially dangerous diseases such as plague, tick-borne encephalitis, typhus. The insect has 3 pairs of legs and can jump high enough. According to scientists, this is due to the fact that in the body of the flea there is an elastic flap, which at the moment of the jump works like a spring, that is, it contracts and expands sharply at the moment of the jump. And the hind legs, which are the longest of the 3 pairs, help to push off the surface better.