Books written on plyometrics and coaches who use plyometrics in the training of athletes do many different kinds of jumps under the umbrella name of plyometrics. Plyometrics involves jumping, but not all jumps are plyometric. For example, skipping rope, easy jumping and skipping, in which you get off the ground only a few inches, should not be considered plyometric. Nor should jumps for greater height be considered plyometric if the feet are in contact for a long period of time as occurs if you bend the knees considerably on each landing.
In a true plyometric jump, the landing and take-off must be executed in .15 seconds or less. If it takes longer, the built-up tension in the muscles, as a result of the eccentric contraction in the landing, is diminished or dissipated. However, jumps that are not truly plyometric in nature are still beneficial. They are used for jump training, which usually precedes plyometric training. It is still important to do both types of jumps to fully develop an athlete especially one who must jump or run in his sport.