Plyometrics, more than jumping onto a box Part 1

Part I will discuss the basic biomechanics of what goes on during plyometrics.

Reactivity, elasticity, and sometimes referred to as buoyancy, plays a very important role in all sports and running. The ability to change direction, sprint, and jump rely heavily on the body’s ability to produce force, relax, and repeat force production.

Taking a look at common practice through visiting professionals, reading material, and learning from other great coaches, a very common variation in each persons approach to development is how they incorporate plyometrics. I hear a common phrase; “most athletes aren’t strong enough so I don’t do them.” Which I will expand upon more later. Some think it is all about how many inches you can jump onto a box. Opposite of that some think it is all about jumping off the tallest box you can. I will also explain why the common test for explosive power (vertical jump) doesn’t quiet tell the whole story.

What Happens When You Jump?
First and for most lets take a look at the biomechanics that come into play when performing a jump in relationship to the stretch shortening cycle (SSC). Taking a look at Hill’s model, two of the three components make a serious contribution. The contractile element (CE) composed of muscle fibers, and the series elastic component (SEC) mainly being the tendon. When performing a jump, these components are stretched, allowing them to store energy, and this energy is released upon rapid contraction. The tendon has the greatest capacity to store energy with little stretch do to it being a rigid structure. Unlike the muscle, which is supple, can stretch much further without storing the same amounts of energy. This would promote the concept that a greater the ability to stretch the tendon during a SSC, the more energy that can be released. This stretch in the tendon would be optimal if the muscle does not stretch. Basically, the more eccentrically a muscle acts within a SSC the less stretch you get out of the tendon.

In part II we will look at how you can apply this information and the specific exercises that utilize this component of the SSC.