How do kangaroos hop?

Kangaroos have large, strong tendons in their hind legs which act as "springs". The springing motion requires less energy than running does, so kangaroos are able to bound for longer distances than other mammals with the standard four legs can run. They have strong back legs and elongated hind feet for bounding.

Kangaroos are able to travel long distances at a high speed, expending very little energy. They are very energy-efficient, and this is linked directly to the physical action of bringing their hind legs up with each hop. Every hop literally refills the lungs.