If you are looking for one of the best ways to jump higher, run faster or hit harder, Plyometrics can be the answer. But why are plyometrics so effective?
Why is plyometrics effective
Plyometrics is a neuro-muscular training, which means it trains the nerves, the muscles and the connection between the nerves and the muscles.
Every muscle is activated by a nerve, this connection is called a motor unit, I have explained that in more detail in the article 4 Unexpected Benefits of Plyometric Training basically the nerve sends a signal to the muscle and the muscle reacts / contracts.
One of the biggest benefits of plyometrics is, that it opens neural pathways, plyometric training increases the firing frequency, which means the signal from the nerve to the muscle travels much faster. With this in mind, we can now understand, why plyometric training is also effective for sports, that do not require explosive efforts.
If we look at an example of a sport, like Powerlifting, which is purely strength dominated, movement velocities are low (literally no explosiveness required). The example below is a random example and demonstrates clearly that movement velocities are low and it takes up to 6 seconds to complete the lift.
Another example from one of our training sessions, which shows clearly, how long a repetition can take
The point here is, even if the movement velocity is low, the muscle fibers need to get activated and plyometric training can help Powerlifters to improve this neuro-muscular activation by opening those neural pathways.
A short discourse into motor units and the physiology of motor units. We have different types of motor units, ranging from low-threshold motor units to high threshold motor units. A low threshold motor unit is a motor unit activating type 1 muscle fibers or slow twitch muscle fibers, a high threshold motor unit is a motor unit activating a type 2x muscle fiber or fast twitch muscle fiber (in between the slow twitch and fast twitch fibers, we also have intermediate fibers called type 2a – for more information on muscle fiber types read the article Muscle Fiber Types and Training).
Once a muscle or muscle group is recruited it follows the so-called size principle or Henneman’s size principle , this principle states that the activation of motor units occurs from low to high threshold.
Have a look at slide 11, it shows the different motor units and the recruitment order
It is debated, that plyometrics or better the adaptations to plyometric training can reverse this recruitment order, which means the body is able to immediately recruit the high-threshold motor units. This is beneficial, because it will reduce the cycle of going from low threshold motor units to medium threshold units to high threshold motor units and gives an advantage in the activation time and will allow for a much quicker and faster muscle contraction.
With this in mind, plyometrics mainly targets and activates the fast twitch muscle fibers, which usually aren’t activated that frequently. It has been shown, that athletes that engage a lot in plyometric training experience a shift in their fiber type spectrum towards more fast-twitch fibers. It has been believed for a long time that changes in muscle fiber types can only occur from fast-twitch to slow-twitch fibers (if athletes engage in a lot of endurance activities). Recent research could demonstrate that changes can also occur from slow and intermediate fibers towards more fast twitch fibers.
What’s the bottom line?
Against common wisdom, it is possible to train yourself to be more explosive and powerful! You might have heard that if you are not explosive, you will never be explosive or that explosiveness is a genetical gift. To a certain extent that is true and I have seen it over and over again, some athletes are just more explosive than others by nature, but I have also seen that athletes can become more explosive if they follow a training program with the right mix of plyometric exercises and certain forms strength training.
All the examples listed above refer to so-called intra-muscular adaptations, which means what happens inside the muscle. We also have inter-muscular adaptations, which are adaptations between different muscles or muscle groups.
So, what are the effects of plyometric training the inter-muscular adaptations or inter-muscular coordination?
The more often you do a plyometric exercise or plyometric drill, the more efficient the body will become in doing this plyometric exercise or plyometric drill. It is not uncommon, that once athletes start out with a plyometric exercise, that the recruitment order of muscle is not in the right sequence. The result is, that the plyometric exercise looks clumsy. This is because muscle groups don’t work in the right sequence and the inter-muscular coordination is inefficient. The more often you train this plyometric exercise, the more efficient the inter-muscular coordination, the sequencing and recruitment order of muscle groups and the result is that the exercise looks more smoothly and effortlessly.
How Plyometrics Work
In order to understand how plyometrics work, we need to first understand how a muscle contraction works. We have two different types of muscle contractions
- an isometric contraction, where the muscle remains in a static position so it’s neither lengthened nor shortened
- isotonic contraction, where the muscle shortens and / or lengthens. Isotonic contractions can further be divided into
- an eccentric contraction, where the muscle is lengthened
- a concentric contraction, where the muscle is shortened
For a more detailed explanation have a look at this video
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
For more information read the article or visit the plyometric training video library