Plyometrics are characterized by an eccentric contraction followed by a concentric contraction. An applied example could be, if we look at the extensor chain (hip extensors, knee extensors and ankle extensors) in a jump, while descending the muscles of the extensor chain contract eccentrically, they are lengthened and while ascending the muscles of the extensor chain contract concentrically, they are shortened.
While descending, the muscle can store elastic energy, which can be released during the ascending phase. This is the reason, why you can jump higher in a countermovement jump (CMJ), than in a squat jump (SJ).
Important to understand for plyometrics and the effect of plyometric training, is that the phase between eccentric phase and concentric phase is called the amortization phase. The shorter this amortization phase, the better the use of elastic energy. Which means in return, too often athletes can’t use the amortization sufficiently and the elastic energy dissipates and can’t be used as effectively as it should be used.
What is the secret, why are plyometrics beneficial?
This cycle of an eccentric contraction followed by a concentric contraction is actually called the stretch-shortening cycle (SSC). I have explained the stretch-shortening cycle and the difference between a long stretch-shortening cycle and a short-stretch shortening cycle in the article A Short Guide To Plyometric Training
What is special about the short stretch-shortening cycle is that it combines a voluntary contraction with an involuntary contraction and consequently leads to higher training adaptations.
For the lower body short SSC activities are jumps focusing on a short ground contact time. You can see an example and the difference between a short SSC and a long SSC in the following video.
For the upper body short SSC activities can be throws with light implements, most often used light medicine balls with the focus on a quick rebound and fast explosive execution. Possible exercises could be medicine ball power drops or medicine wall drills with a strong focus on keeping the time it takes from receiving the medicine ball to releasing the medicine ball as short as possible. Remember it should be a short SSC, so short contact times.
Long SSC activities for the upper body are usually done with heavier implements, heavy medicine balls, sand bags, kettle bells, etc If we are looking for an equivalent for the medicine ball power drop as a short SSC exercise an example for a long SSC exercise can be chest passes with a heavy medicine ball or a Bench Throw in a Smith machine.
Have a look at the example below, which makes it clearer. The upper video is an MB Power Drop with a short contact time and can be classified as a short stretch-shortening cycle upper body exercise and the video below is an MB Chest Pass and can be classified as a long stretch-shortening cycle upper body exercise.
Important here, don’t get married to an exercise or training mode, whether it’s a medicine ball or a kettle bell. Think what you want to achieve first and then select the right exercise to achieve that.
What Muscles Do Plyometrics Work
I have mentioned before, that I usually don’t think in muscles in isolation, but much rather think in movements or muscle chains. The simple reason is that in most sports, you rarely use a muscle in isolation, you use a chain of muscles in a sequence to perform a movement.
To use the example from before, if you want to jump you use the extensor chain of the lower body, the hip extensors, knee extensors and ankle extensors. The main corresponding muscles and muscle groups would be the gluteus maximus for the hip extension, the quadriceps for the knee extension and the soleus and gastrocnemius for the ankle extension.
If we take the example of the medicine ball power drop or medicine ball chest pass, which is essentially the same movement as a Bench Press, it also uses the same major muscle groups and muscle chain as the Bench Press (the pectoralis major, the deltoids and the triceps).
However, it is important to note, that plyometrics work better for muscle chains that perform a ‘pushing movement’ and exercises with an ascending strength curve (we discussed the topic of ascending strength curves in the article / video How Strength Training Works – Accommodating Resistance)
Let me explain what I mean by ‘pushing movements’ vs ‘pulling movements’.
A typical ‘pushing movement’ could be a vertical push or horizontal push for the upper body, like a Military Press (vertical push) or a Bench Press (horizontal push) or a squat variation for the lower body. That could be a bi-lateral Squat, such as the Back Squat, Front Squat or Overhead Squat or a uni-lateral Squat, such as the Bulgarian Split Squat, the Split Squat or variations like Lunges or Step-Ups.
Typical ‘pulling movement’ could be a vertical pull or horizontal pull for the upper body, like a Pull Up (vertical pull) or a Bench Row / Bench Pull (horizontal pull).
A typical ‘pushing movements’ follows the eccentric-concentric contraction cycle, where the muscle groups can effectively store elastic energy in the eccentric contraction and use the stored energy in the following concentric contraction.
In a ‘pulling movement’ the contraction cycle is reversed, it starts with a concentric contraction which is followed by an eccentric contraction. Therefore plyometrics don’t work as well for ‘pulling movements’ as opposed to ‘pushing movements’.
There are ways to work around that in ‘pulling movements’, but it still doesn’t work as well compared to ‘pushing movements’.
Concluding Why Plyometrics are effective
Plyometric training can
- help you to activate your muscle fibers faster
- lead to more fast-twitch muscle fibers
- improve coordination and technique
Once you understand the mechanics behind plyometrics, how to use those mechanics to your advantage and apply that in your plyometric training, you will be faster and more explosive and as a result jump higher, run faster and hit harder.
More information on Plyometric Training
A Short Guide to Plyometric Training
4 Unexpected Benefits of Plyometric Training
How much can Plyometrics increase your Vertical?
How often should you do Plyometric Training?
How to build a Jump Box for Plyometrics
Why Are Plyometrics Good For You?
How Plyometrics Increase Your Vertical
What are the Benefits of Plyometric Training?
What Is Plyometric Training?
For more information read the article or visit the plyometric training video library