Have you heard that plyometric training is dangerous? It is like driving a car, if you don’t know how to do it, it is pretty dangerous…
On the other hand, if you know what you are doing and have a well-planned plyometric training plan with the right plyometric progressions and intensities, plyometric training can be very rewarding.
What Is Plyometric Training
At the core of plyometric training lies the stretch-shortening cycle (SSC), so let’s take a quick moment to understand what the stretch-shortening cycle is.
What is the stretch-shortening cycle
During the stretch-shortening cycle a muscle gets stretched or lengthened (eccentric contraction), followed by an instant shortening (concentric contraction). The underlying mechanism of the SSC is, that during the lengthening or eccentric contraction the muscle and tendons can store energy, often named as ‘elastic energy’, and this energy can be released during the shortening or concentric contraction.
And it gets even better…
The energy stored during the eccentric phase can augment the force of the concentric contraction, which means the concentric contraction is stronger if it’s preceeded by an eccentric contraction.
As a very practical example, figure two scenarios on a Bench Press.
Scenario 1, you do a regular Bench Press, you are lying on a bench, start with the arms extended, lower the bar to your chest and press the bar back up.
Scenario 2, you are lying on the bench, but this time you start with the bar on your chest (so you don’t lower it) and press the bar back up.
In which scenario will you be able to lift more weight (if you don’t know the answer try it out yourself)?
In scenario 1 you will be able to lift more weight, this is the stretch-shortening cycle in action. The muscle and tendons can store energy when you lower the bar to your chest and can use the energy, when you press the bar back up.
This phenomenon of the stretch-shortening cycle can be seen in almost every sporting action, whether it’s running, jumping, throwing, kicking, hitting, etc.
The stretch-shortening cycle can be classified into
- Short stretch-shortening cycle
- Long stretch-shortening cycle
The short stretch-shortening cycle makes use of an involuntary reflex that complements and augments the voluntary force production. When applied to jumping or running the short stretch-shortening cycle can be classified as ground contact times of below 180-200 ms (you find different specifications in the scientific literature, in most cases it’s 180 ms or 200 ms).
The long stretch shortening cycle is classified can be classified of ground contact times above 200 ms.
You can see in the following video the same plyometric exercise, one focusing on a short ground contact time (video on the top) and the other focusing at a longer on a longer ground contact time (video below).
To sum it up, the stretch-shortening cycle is an integral part of plyometrics training, that makes use of active stretch or eccentric contraction of a muscle immediately followed by the shortening or concentric contraction of that same muscle. Especially the short stretch-shortening cycle, which makes use of the involuntary stretch reflex and helps to intensify the voluntary force production and therefore leads to greater training adaptation.
Benefits Of Plyometrics Training
When I was working with our Olympic Beach Volleyball players I heard from the Beach Volleyball coaches and players ‘We don’t do Plyometrics, because we don’t have short contact times in the sand.’
While that is certainly true, plyometric training is not only about short contact times, ‘Plyometric training opens neural pathways’ as Vern Gambetta described it in his book ‘Athletic Development – The Art & Science of Functional Sports Conditioning’
But what does it actually mean?
The adaptations to plyometric training are not only limited to the the stretch-shortening cycle, as I have outlined in the article The 101 of Power Training for Beginners the human body uses three mechanisms for muscular activation
- Recruitment of muscle fibres, how many motor units or muscle fibres can be activated
- Firing frequency of muscle fibres, how fast motor units or muscle fibres can be activated
- Synchronization of muscle fibres, how efficient motor units or muscle fibres are activated
Plyometric training improves the firing frequency of motor units and the synchronization of motor units. Firing frequency helps that muscle fibres are activated faster, which is very important if you are participating in a sport where speed and power is required. Synchronization trains that for one, the prime movers (the muscles that are responsible for a certain movement) are activated at the same time and which leads to greater force production. On the other side it helps that the opposing muscle groups are inhibited, which is also known as reciprocal inhibition and simply means while some muscle groups produce force to perform a certain movement, the opposing muscle groups are ‘switched off’ and don’t work against the force producing muscle groups.
How Often Should You Do Plyometrics?
The answer to the question about the ideal training frequency is dependant on a few factors, most importantly on the intensity and the volume of the plyometric training.
The higher the intensity, the less frequent the plyometric training should be carried out. For the simple reason, that the higher the intensity, the higher the impact on the nervous system and muscular-sceletal system.
But how what is a high intensity and what is a low intensity?
If you look at the following video, this is an example for a low-intensity plyometric exercise (disregarding that it is multilateral), because the hurdles are small and there is not a lot of impact on landing and taking off.
Eventhough it is the same exercise, the following video shows a higher intensity level as the previous video just for the simple fact, that the hurdles are a bit higher and therefore the impact is also higher.
And just to make things a bit clearer, in the following video the intensity is even higher than in the previous video as you can see, higher hurdles and a higher resulting impact.
The skilled coaches eye will see, that the first ground contact of the three ground contact is the longest.
For lower intensity plyometric exercises as in the first video you can chose a training frequency of 2 – 3 plyometric trainings a week with a day of rest in between, for higher intensity plyometric exercises you can choose a training frequency of 1 – 2 plyometric trainings a week with 2 – 3 days of rest in between.
Which plyometric exercises should you choose?
The answer to that question depends on what you want to achieve with the plyometric training and whether you are ready to do those exercises.
Strictly speaking, the higher the intensity, the higher the potential adaptation, but this is only true if the plyometric exercise can be mastered in a safe way with proper execution.
Trust me, I have seen people get hurt performing plyometric exercises they were not ready for!
Even with our Olympians, every season we build up the plyometric training carefully, starting out with low-intensity exercises at the start of the season and progress over time to higher intensity exercises and we monitor volume and intensity carefully.
As a very rough outline, we start with an exercise where we purely focus on absorbing the landing (eccentric only), an example of such a plyometric exercise could be altitude landings. Have a have a look at the following video, this is already a progression and performed single-legged
After that, we progress to plyometric exercises low impact, an example could be mini-hurdle jumps or box jumps (box jumps take out the impact of landing)
and progress to plyometric exercises with higher impact over time.
It is worth mentioning that the time frame from start of the season to the introduction of high-intensity plyometric exercises takes at least 8 weeks, depending on the level of the athlete and the training history of the athlete.
Plyometric Training Conclusions
Everything that is worthwhile takes time to learn and it’s no different with plyometric training. You need to learn the different plyometric exercises and plyometric exercise progression to reap the benefits of plyometric training.
If you know how to make use of the stretch-shortening cycle, plyometric training leads to adaptations that make you faster and more powerful.