The Rules of Gravity: Plyometrics


Are you or your clients ready for plyometrics?

First let’s define what plyometric exercises are. Plyometrics are exercises that enable a muscle to reach maximal force in the shortest amount of time. They are categorized under muscular power. Therefore they are quick powerful movements involving a pre-stretch, or countermovement of the muscle group being used, known as the stretch shortening cycle.

The stretch shortening cycle happens when a musculotendinous unit is elongated in an eccentric manner and what is known as the series elastic component, (SEC) undergoes elongation acting much like a spring being stretched out and lengthened, which in turn causes elastic energy to be stored. When this is immediately followed by a concentric contraction, this stored energy contributes to the total force production in which the muscles and tendons return to their natural unstretched state. This transition period between the eccentric and concentric contractions is known as the amortization phase. If a concentric contraction does not take place immediately after the eccentric loading phase or the (SEC), then this stored energy is lost and it is dissipated as heat.

Therefore, when the elastic energy within the musculotendinous complex is increased by the SEC of a rapid eccentric action, and it is immediately followed by an instantaneous concentric contraction. The stored energy from the SEC is released, increasing total force production.

Now that we have a better understanding of what happens physiologically with plyometric activity, there are a battery of tests to identify if an athlete is ready for this type of training. The following tests will determine if the athlete possess a sufficient baseline of speed, strength, and agility to perform plyometric work. Prior to doing these tests the athlete must demonstrate proper form and mechanics for each exercise to reduce risk of injury and maximize the benefit of plyometrics within a strength training program.

For upper body strength an athlete who weighs less than 220 lbs, should be able to bench press 1.5 times their own body weight for a one repetition max (1RM). Athletes over 220 lbs should be able to bench 1.0 times their body weight for a 1RM. To test speed they should be able to perform 5 bench presses with 60% of their body weight in 5 seconds or less. Both need to be done with perfect form.

Lower body strength requirements for athletes would to be able to barbell squat at least 1.5 times their body weight for a 1RM. For speed they must be able to perform 5 repetitions of the squat at 60% of their 1RM in 5 seconds or less. Both need to be done with proper form and no biomechanical breakdown.

Another important requirement is that the athlete must be able to demonstrate good eccentric loading techniques. This is how well they can control the speed in an eccentric manner, letting the muscles absorb the impact of weight resistance to minimize joint damage. Let’s take a step up for example. The landing phase of a step up is when the foot comes in contact with the floor as they step back down from an elevated platform, returning to start position. The athlete must demonstrate good control in the eccentric contraction to land in a controlled manner, rather than slamming down on the floor with very little control. Step up’s are plyometric in nature and are considered to be a low intensity one.

These tests are a good method of testing your clients or athletes to see if they fulfill the minimal standards for performing high intensity plyometrics.

Start with low intensity, and work up to a higher intensity level. This way you can monitor their mechanics and progression.

So the next time you perform plyometrics with a client or athlete, take them through these tests first to minimize any chance of injury. You can’t just have someone do plyometrics if they don’t fulfill these speed, strength, and eccentric loading techniques.

Jon Torerk, CSCS

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Author: Piyawut Sutthiruk

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