Plyometric training is used in a wide variety of sports to increase athletic performance. Plyometrics is a form of training designed to increase muscular power. There has been little research conducted as to what constitutes optimal guidelines for a plyometrics program, however what has been proven is that it is an effective method of training for increasing muscular power where there already exists a solid strength base.
Plyometric training is a form of training that allows a muscle to reach maximum force in the shortest possible time. There are no other training modalities that allow this so plyometrics is the optimal training method for the development of power.
How Does Plyometric Training Work?
If a muscle is eccentrically (the lengthening part) contracted immediately prior to a concentric contraction it is able to produce greater force than if it were simply contracting straight from a rested position. This is demonstrated when a person dips down slightly just before performing a vertical jump. Without that dip and immediate jump the athlete would not generate as much force for the jump.
There are several texts and much theory to explain how and why plyometric training actually works. The two most feasible and popular models are the mechanical model and the neuromuscular model.
The Mechanical Model
The mechanical model suggests that there is elastic energy stored in the muscles and tendons. This makes perfect sense because muscles and tendons are elastic to a certain extent. The best way to get an idea of this is to look at a rubber band. Stretch the rubber band out to maximum length. At this position it has an enormous amount of stored elastic energy. Now let it go and see what happens. It will generally spring out from your hands with great force. This is how a slingshot works.
The muscles are said to work in the same way. By lengthening the muscle first you are building up elastic energy that is stored and then released when the muscle in concentrically contracted. This model makes a lot of sense but there a few holes in this theory, which leads me to believe that there is not simply one model that explains why plyometric training works. It makes more sense for both the mechanical and the neuromuscular model to be a combined effort.
You see, the hole I can see is that when the muscle is “pre-stretched” and immediately contracted it produces more force. However when that pre-stretch is delayed by more than a second or two the potential energy is lost. Mechanically this makes no sense because stored elastic energy should be able to be delayed and still produce force. This is why the neuromuscular model must play a role.
The Neuromuscular Model
The neuromuscular model suggests that the nervous system plays a role in producing more force during plyometric training. This is due to the stretch reflex, which is a protective response. When a muscle is stretched the neuromuscular system detects it and endeavours to protect it from injury. It does this by rapidly contracting to prevent it from overstretching and bring it back to its original length.
Flexibility is also of major importance when you consider any method of training that involves extremely dynamic movement. In addition to that, you really need to take care of your joints and ensure they can withstand the impact. I recommend the following two resources for flexibility training and joint strength.
The stretch reflex increases the activity of the stretched or eccentrically contracted muscle allowing it to produce more force in the other direction. This results in a powerful stop where the stretch reflex puts a hold on further stretching like putting on the brakes. When this occurs there is the potential for a powerful contraction to counteract the stretch.
As I mentioned previously, this explains what the mechanical model doesn’t. If the muscle is not immediately contracted after the stretch reflex the neuromuscular system then rapidly adapts to the stretched position and weakens this action. It’s like when you do a hamstring stretch to the maximum extent you can handle. At first it hurts but if the stretch is held for a length of time you get used to it and are able to even stretch a little further. This is not the muscles getting longer, that would be impossible in such a short time. It is the stretch reflex releasing its hold a little and allowing the muscle to lengthen a little more. This completely negates the potential of the stretch reflex to produce force.
There is research coming out now that suggests the mechanical model and the neuromuscular model both play a role in the increased force production of a muscle during plyometric training.
Should You Do Plyometric Training?
There is a lot of debate for and against plyometric training. On one side you have the coaches that have seen it work for many years and support it in training athletes. There are also those that do not recommend it due to injury potential and other risks as well as insufficient research.
Does It Work?
The first argument is one of effectiveness. It is argued whether plyometric training will produce results that can’t be gained through other means. It is hard to say whether this is a valid argument or not. Most elite coaches and athletes believe that it does indeed work and they have been doing it for years with amazing results.
When the body undergoes any sort of training there is a physiological response where the body then adapts to the training stimulus so that the next time you engage in a similar activity you are better equipped to do it more efficiently and effectively. If this were not true then people would not be able to get fitter through exercise and therefore any sort of exercise or fitness training would be a complete waste of time.
Plyometric training needs to have some form of adaptive response, otherwise there is no point doing it. As all physical training has an adaptive response when the body reaches a certain threshold, plyometric training must be doing something. But what is that something? What exactly is the adaptive response?
There are several theories as to what the adaptive response to plyometric training could be. We have already looked at the acute, immediate response, which explains how more force is produced when the muscle is first eccentrically contracted. There are two adaptive responses that are almost certainly occurring long term…
The first is in response to the mechanical model. The muscle is repeatedly put under this mechanical strain and forced to utilise the stored energy that it generates when a muscle is lengthened. In response to that the muscle itself changes slightly by becoming a tougher “elastic band”. This happens by changing the elastic behaviour of the muscle. If an elastic band is made stronger and tighter then it has more stored energy when you stretch it to its maximum length.
The second adaptation is in response to the neuromuscular model, obviously. When the stretch reflex is put to use under such circumstances on a regular basis it needs to adapt in some way. So in response to being activated the stretch reflex then kicks in more rapidly and causes the muscle to perform the opposing concentric contraction more forcefully.
Despite these scientific explanations, plyometric training has been used for a long time with positive results. Athletes, coaches and exercise physiologists scrutinise the results of everything they do. So there is much data that supports the effectiveness of plyometric training that does not entirely explain why that result was obtained. I would advise adding it to you training regime if speed and power are required.
Plyometric training is an extremely high impact training method. For this reason you should not undergo this form of training if you are not first prepared. The following are three prerequisites before starting a plyometric training programme.
Plyometrics is a great way to build power and a corresponding increase in speed. It should be utilised by everyone needing power and speed increases or even for non-athletes looking to get a bit more of an edge in their fitness efforts.
Keep an eye on our training section for power training and plyometric training programmes for various purposes.