The Basics of Plyometrics
Plyometrics provide a great foundation in athletics. When done correctly, plyometrics act like a spring in the body. They deliver injury reduction and power the body to greater athleticism. Your plyometric program must be systematic and eased into slowly to reduce injuries.
What are plyometrics?
If you’ve been in sports for a while no doubt you’ve heard the term. Plyometrics use something called the stretch shortening cycle. This cycle consists of three phases; the eccentric contraction, amortization phase and concentric phase.
Eccentric Phase
The eccentric phase comes first. The eccentric phase allows the muscles to stretch during which energy is built up. Without this pre stretch you’ll find yourself less athletic and less explosive. Try this. Stand in one place with your legs straight. Lower yourself quickly and immediately jump up as high as you can. So that you don’t have to think about it, just do a normal vertical jump.
Second, bend your knees so that you are in the down position of a vertical jump. Hold that position for a second or two. Now jump up as high as you can. Mark that position. Do a few repetitions of each type of jump. You should find yourself with a greater vertical leap in the first scenario. Without the eccentric phase the energy that could be built up for an explosive concentric phase wont be there making you, again, less powerful.
You see the eccentric contraction everywhere. Here are a few examples:
- Running
- Throwing a ball
- Jumping
- Hoping
IIn each of these examples you’ll see the person first perform an eccentric contraction like a pitcher in baseball pulling his arm back or a soccer pulling her leg back behind the body for a powerful kick. Try pulling your leg back, holding it in position for a couple seconds then kicking. I bet you didn’t kick quite as far. This leads us to our next phase.
Amortization Phase
During the eccentric phase lots of energy is built up. The body uses this energy to create greater feats of athleticism. But if you pause too long after the eccentric phase that energy dissipates and you lose the benefit caused by the eccentric contraction.
TThe amortization phase is between the eccentric and concentric phases. The key here-don’t pause in between the two phases too long or you'll lose energy.
Concentric Phase
This is the shortening of the muscle that creates the desired action. It is the soccer player moving her leg forward to kick the ball, it’s the pitcher moving his arm forward to throw the ball, it’s the soccer player jumping up to win a header. The concentric phase expresses the energy built up during the eccentric phase (and not lost by too long a pause in the amortization phase).
How do plyometrics help the body?
We all know females are more apt to ACL injuries than their male counterparts. Some think this is because of anatomical, hormonal and neuromuscular difference. It is the neuromuscular component that we can affect through training. One study showed that “pre- and in-season neuromuscular training with an emphasis on plyometrics and strengthening exercises was effective at preventing ACL injury in female athletes, especially in those under 18 years of age.” (1)
In soccer, explosiveness used in Jumps, sprints, agility and more is required. Another study looked at the affect of plyometrics on performance in some of the measure previously listed. In this study children around the age of 13 years old followed an eight week plyometric training regimen. They tested 6 areas: 10-meter sprint, agility, 3 vertical jump tests, and multiple bounds test. The plyometric training reduced the 10-m sprint time (-2.1%) and agility test time (-9.6%) and helped with increases in jump height. This study demonstrated that a plyometric program within soccer practice can improve explosiveness in young children. (2)
Summary
Plyometric actions happen in everyday life. Most if not all the time we just don’t think about it. It’s one of the ways the body provides greater athletic prowess to our every day movements. When used correctly plyometric training can be a source of greater athleticism in athletes as well. When used incorrectly it can be the source of injury. That is why you need to progress your athletes in control and now allow them to go straight to things like depth jumps.
In future articles I hope to delve more into how to progress plyometrics, how to do them, and provide some good examples of exercises.
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