Plyometrics is a type of exercise that uses explosive movements to develop muscular power, the ability to generate a large amount of force quickly.

For example; think of a Kangaroo, if a kangaroo needed to use 100% new energy to contract its leg muscles every time it jumped, it would not be able to jump very far consistently. However, because of the muscles’ ability to store energy from its previous jump before like a spring, the kangaroo only needs to use a fraction of the total energy in the jump.

Similarly, when you throw a ball, you don’t pause when your arm is fully extended behind you.

Elastic energy is created in the muscles and tendons and stored as a result of a rapid stretch. This stored energy is then released when the stretch is followed immediately by a concentric muscle action.

I highly recommend this method of training!

Read more here: http://www.sport-fitness-advisor.com
And here: http://en.wikipedia.org/wiki/Plyometrics