Plyometric training is based on the naturally occurring physiological phenomenon of the stretch shortening cycle of muscle action. It is training the stretch shortening cycle of muscle action to enhance the subsequent concentric action. The utilization of the stretch shortening is essential for efficient human movement. It is a quality of the muscle action that is highly trainable and adaptable. Over the years much confusion has arisen about this method of training. Much of the confusion has come from the name itself. It first appeared in coaching literature in the late 1960’s, but that is not when it was first used in training. Jumping, hopping, and bounding activities have been used throughout the ages, although it was not until the mid twentieth century that the use of these activities was systematically applied to athletic performance enhancement. It is scientifically accurate and more descriptive to call this method elastic/ reactive training but that is cumbersome, hence the term plyometrics is more commonly used. Elastic/ reactive training is certainly more descriptive of the goals of the training method and the physiological demands, because essentially we are training the elastic properties of the muscle to be more reactive to the ground. The goals of Plyometric training are threefold:
- First and foremost to raise explosive power.
- To learn to better attenuate ground forces regardless of the event or sport.
- To learn to be able to tolerate and use greater stretch loads, in essence to increase muscle stiffness.
The last point demands a bit more explanation. Musculotendinous stiffness is the key to elastic/reactive training. It is highly related to the body’s ability to store and reuse elastic energy from running and jumping. The concept of stiffness is sometimes confusing because we tend to equate stiffness with a lack of flexibility, for explosive movements this is not the case. Essentially a stiff muscle will develop a high degree of tension as it is stretched. This is very desirable to raise explosiveness. Conversely a non-stiff muscle will collapse and absorb elastic energy; it does not react as actively to the ground, therefore it will produce significantly less explosiveness. A simple analogy to help to understand stiffness is to compare a soft rubber playground ball and a golf ball. If both balls were dropped onto a hard concrete surface the golf ball would react rapidly and the playground ball would react slowly to the ground. In plyometic training in order to optimize ground reaction forces we want the golf ball type reaction. A stiff muscle is able to produce optimum amounts of reactive force in a short period of time. Plyometric training is not a stand alone training method; it is highly compatible and significantly enhanced by strength training. It is also closely related to speed development. Most importantly it is NOT a conditioning tool! Because of the explosive nature of the work it is of high neural demand, therefore it should not be used for conditioning. It should almost never be trained in a climate of fatigue, with a few notable exceptions. Those exceptions are sports that demand power endurance like soccer, rugby, basketball, 400 meters or 400 meter hurdles. In those sports the fatigue element is only introduced after the technical component of the exercise is mastered. This will minimize risk of injury. The stimulus for adaptation is not volume it is intensity. Nothing should ever compromise the intensity of the movements. Too much emphasis has been placed on volume in terms of the number of contacts. Over the years as with a better understanding of the application of the method, the number of contacts in a training session and a microcycle has been significantly reduced. In the past it was not uncommon to see 300- 400 contacts in a session, today a high volume session is in the range of 90- 120 contacts with a range of 250 – 400 contacts for a microcycle. More is definitely not better. If used properly it is a highly effective tool to stimulate the nervous system, but if used improperly it can have the opposite and dull, if not deaden the nervous system. Plyometric training consists of three very basic movements. Jumping characterized by two foot landings is the most fundamental. Hopping is characterized by one foot landing. Due to the fact that body weight is supported on one leg on landing makes hopping more stressful. Bounding is characterized by alternate leg takeoff. This is also quite demanding because all the bodyweight is supported on one in the landings. The complexity in Plyometric training comes from combining these movements and their derivatives.