Jumping is a normal part of human movement, and it was and still is an essential skill for survival. Jumping is also an excellent training method to develop lower body power and explosiveness, and it’s a fundamental skill for many different sports.
With the shear simplicity and beauty of the “jump” in human performance and function, the training methods and terminology that surrounds jumping are confusing and in some cases very inaccurate. This classification of exercise is often referred to by several different names including: elastic strength development (ESD), reactive strength development, plyometric training, and stretch shorten cycle (SSC) training.
The common thread with all these terms (except for one) is that they reflect the involvement of lengthening and shortening muscle actions. With that said, the most popular term and the one that does not reflect its true definition is the term plyometric training yet plyometric training is the one most commonly used.
Here’s why the term plyometric training is inaccurate and inappropriate:
The word plyometric or pliometric was first coined back in 1938 by two muscle phyisologists by the name of Hubbard and Stetson (Hubbard et al., 1938). They observed that a muscle contraction, which is essentially an all or none phenomenon, occurred with respect to three conditions: miometric or shortening, isometric or no change in length, and pliometric or lengthening (Faulkner, 2003).
A muscle contraction at the ultra-cellular level is more or less the same regardless of whether a muscle lengthens, stays the same or shortens. This is why they didn’t use the phrase muscle contraction and instead opted for the phrase muscle action when referring to the direction of the muscle contraction.
In all cases the direction of the muscle contraction (i.e. it’s action) is determined by the external load. It is the load that determines whether or not the muscle shortens (miometric muscle action), stays the same (isometric muscle action), or lengthens (pliometric muscle action).
Fast forward to the year 2011 and we know how the story unfolded. The word isometric stuck with sport and fitness professionals, the word miometric was replaced with the term concentric muscle action and the word plyometric morphed into this category of exercise that involved lengthening and shortening muscle actions such as jumping.
Now, you can say that I’m splitting hairs but I think as fitness and sport performance professionals we should use the words that best describe and reflect what we are trying to accomplish. The textbook definition of concentric is “of or denoting circles, arcs or other shapes that share the same centre”, and the textbook definition of eccentric is “a strange and unconventional person or an object not placed centrally.” Nowhere in those definitions does the concept of shortening or lengthening arise.
So the question is this: why did isometric muscle action stick, miometric muscle action vanish into obscurity, and the term plyometric become synonymous with a form of training designed to improve the ability to switch from a lengthening muscle action to a shortening muscle action? I’m not sure I have the answer for you but many prominent muscle physiologists, biomechanists, and strength and power researchers have advocated that the terminology be changed and that we strive for accuracy in our definitions (Faulkner, 2003).
With all that said, I’m going to suggest that the preferred terminology for the category of exercise under which jumping type movements fall is either Elastic Strength Development or Reactive Strength Development. Both terms have popularity in fitness and sport performance circles, and both do a better job of describing what is actually being targeted and accomplished with this form of training. You may think that this is meaningless in the grand scheme of things but as an academic and a strength coach, I strive to be as accurate and precise as possible with the words that I use.
I realize I’m not going to change the entire culture of strength coaches and personal trainers but for those of you who take pride in what you do, and want to be as accurate as possible with the words you throw around, I strongly suggest you think about stopping the use of the word plyometric to denote training involving shortening and lengthening muscle actions.
In my next blog I will expand on jump mechanics and the considerations for Elastic Strength Development or Plyometric Training for those of you who just plan to stick with convention regardless of the obvious inaccuracy in the term. For a more detailed review on the history of these terms and suggestions from an expert, see the article authored by John Faulkner that was referenced in this blog.
Hubbard & Stetson. J Physiol. 124: 300-313. 1938
Faulker. J Appl Physiol. 95: 455-459. 2003