Some would argue that this article is misplaced in a section on core training. After all, the explosive power in most plyometric exercises comes from the legs. But plyometrics requires a pre-load and can involve both vertical, lateral, and rotational movements - across, around and through the core. [This is excerpted and edited from a longer technical/academic paper by the two authors.]

by James C. Murphy, MHK, CSCS, MNLP
University of British Columbia, Vancouver, BC
and Coop DeRenne, Ph.D.
University of Hawaii, Honolulu, HI

Plyometrics is defined as the deceleration of a mass (eccentric action) immediately followed by the acceleration of the mass (concentric action) in the opposite direction. Plyometrics center around a muscle’s capacity to exert its maximal force output in a minimal amount of time. Success depends on the speed at which muscular force can be generated.

Another definition of plyometrics:  A quick powerful movement involving a prestretching of the muscle, thereby activating the stretch-shortening cycle (SSC).  The prestretch is also referred to as elastic loading.


The purpose of plyometric training is to increase the excitability of the neurological receptors for improved reactivity of the neuromuscular system.  It can be referred to as reactive neuromuscular training. 

The clap push-up is an example of a plyometric exercise.  The downward phase is the prestretching (eccentric action) and the upward acceleration phase is the concentric action. 

Another example of how the prestretch works is the standing vertical jump test.  When an athlete attempts a maximum vertical jump, he thrusts his arms down immediately before the explosive movement upward.  This downward arm action helps facilitate the opposite upward movement by preloading the lower legs and flexing the knees loading the gastrocnemius and soleus.  Another way to look at plyometrics is that the muscle is stretched while active, resulting in greater force capability during subsequent concentric contraction than could be generated during a concentric contraction from a static position not preceded by a stretch.


Plyometrics appear to bridge the gap between pure strength training and the specific skills used in competition.  It involves body weight that is accelerated by gravity and musculature, providing a force and velocity greater than that of machine weights.
The importance of training with plyometrics for power type sports has been well documented.  Darden (6) summed it up:

Other researchers concur.  Numerous studies have established the effectiveness of plyometric drills in improving power. Wathen states that plyometric exercises are very similar to actual movements used in baseball, and that when perfected, the athletes are better able to accelerate their bodies and or sports implements (balls) generating greater force at higher velocities.  Wilk et al. state that in no single athletic endeavor is the use of elastic loading to produce a maximal explosion (concentrically and eccentrically) more evident than in throwing a baseball.   
   

Some examples of plyometrics are bounders, high knees, ice skater jumps, lateral hurdle hops, and consecutive broad jumps...

• Bounders are alternate leg jumping drills where the athlete is trying to get as much distance and air time as possible with each jump. 
• High knee drills are done with a minimum amount of time spent on the ground. 
• Ice skater jumps are 45 degree angle jumps, also known as the zigzag drill. 
• For lateral hurdle hops a small cone is used, jumping back and forth. 
• Broad jumps are both legs, generally three in a row.

Other plyometric exercises involve the core and upper body more specifically. Look for a companion article which includes medicine ball plyometrics.