Plyometrics is perhaps the best method to develop quickness and explosiveness. It was created by the Soviets, more specifically, Yuri Verkhoshansky, to train the muscles to react in a very quick, explosive manner. Because of its great effectiveness, plyometrics is now used in the training of athletes in almost all sports and it has even permeated the fitness field. However, very often the objectives of using plyometrics in fitness are not exactly the same as when it is used in sports. There are also differences in when plyometrics is introduced into the training program.
For example, when you incorporate plyometrics into your training program, it should be done after you have developed a strength base. This is needed not only to prevent injury, but to get the maximum benefit from a true plyometric training program. Note that plyometrics, when done correctly, is a very intense activity, much more so than lifting weights, even heavy weights. By having an adequate strength base, you not only lessen the chance of injury but make the training program more effective.
Studies that compare plyometric workouts with strength workouts to see which one is more effective, should be disregarded, mainly because plyometrics should utilize the strength gains and literally convert the strength into speed and explosiveness. If you use plyometrics to gain strength, you will not be utilizing the maximum potential of the muscle for quickness and speed. Instead, the plyometric exercises will be done at a slower rate and not as intensely as they should be. They are usually of the preparatory type of plyometrics which consist of easy jumps, hops, skips, and so on, and not maximally taxing depth jumps and other types of explosive jumps that require tremendous power.
See Secrets of Soviet Sports Fitness and back issues of the Fitness and Sports Review International (Soviet Sports Review) for more information.