29 September 2015
Plyometric training is often called jump training with the two terms being used interchangeably. This is best avoided as the two terms are not the same thing and although plyometric training often involves jumps, jump training is not necessarily plyometric.
Let’s try to clarify this a little by looking at what each variation actually stands for and what is required to achieve a plyometric stimulus.
We can say quite simply that jump training is “training that involves jumping” and this is perfectly descriptive, if a little vague.
Jump training typically involves a speed element (it’s hard to jump slowly) and displays an enhanced power component compared to slow heavier lifting. Although the speed of movement is quicker than in other exercises such as a typical weighted back squat, jumps are often still not plyometric in nature.
Squatting down, for example, pausing then jumping up explosively would be considered a strength based exercise (it is not plyometric). A counter movement jump, where we start standing and rapidly flex the hips, knees and ankles before powerfully extending in to a jump, could be plyometric, if performed well (with the required level of speed).The key here comes from the point where we change direction from lowering the body by flexing the lower limbs to raising the body by extending the lower limbs. This process must be extremely fast in order for the movement to make use of a stretch shortening cycle and be classed as plyometric.
Plyometric exercise uses the stretch shortening cycle in order to generate more force in a shorter time frame. A stretch shortening cycle occurs when a muscle is stretched by lengthening (eccentric) and then rapidly shortens (concentric) which produces a powerful contraction. Lengthening the muscle (as in absorbing a jump landing when the legs flex) stretches the muscle fibres and connective tissue (fascia and tendons) which preloads them with elastic energy. This elastic energy can then be used to contribute to the subsequent concentric action, creating more force, which propels the body up in to the jump. If the turn-around from muscle lengthening (on landing) to muscle shortening (propelling to take off) is too long, the stored elastic energy ebbs away and the effects are lost. For an exercise to be classes as plyometric this turn-around time (amortisation) must be less than 0.2 seconds, so if you hang around on the ground you lose the plyometric effect.
Jump training can be an excellent training method and suits some situations well (static starts for example), however true plyometric training will produce more force and increase the rate at which force can be developed. As many sporting situations (such as sprinting) will require the application of force to be with the 0.2 second timeframe to be effective, plyometric training’ is an extremely important part of the training toolbox.
There are many benefits to these styles of training, but we must be clear on which we are actually using when we train. This goes far beyond being picky about names and will determine the results of a training programme.
To be plyometric the exercise must use the stretch shortening cycle and not be more than 0.2 seconds in duration. If you’re on the ground for any longer you’re not doing plyometric training.