Monday, April 15, 2013

Is a certain level of strength necessary before engaging in plyometrics?

Is a certain level of strength necessary before engaging in plyometrics?

A certain level of strength is necessary for optimal performance in plyometric movements and added strength can also bring enhanced reactive strength.  To explain this, lets use the example of performing a depth jump.  During a depth jump you stand on a box or bench, drop off, and at ground contact you absorb the impact, your muscle lock up, your tendons stretch and gather energy, then you reverse direction and jump up.  Now, whenever you step off the box gravity is quickly bringing you down to the ground.  Upon immediate impact your muscles are trying to lock up and stabilize.  At that point they are subjected to tension and forces up to 9 times or more your bodyweight.  If you do not have enough strength to absorb these forces your body will do one of 2 things:

1.   It will shut down the stretch reflex to avoid injury
2.   You will take too long absorbing the forces to utilize the stretch shortening response.

The greater your strength the more force youll be able to gather and put out and the quicker youll be able to do it.  A minimal level of muscular strength is necessary to absorb the high forces.

So what is the minimal amount of strength I need?

Many people ask this question and the entire topic has really created a lot of confusion in strength and conditioning community.  Many coaches say that athletes should be able to squat at least 1.5 times their bodyweight before performing any plyometric training.  This is both true and false.  Remember that from their eastern roots originally plyometrics consisted of only 2 exercises, depth jumps and shock” jumps.  Remember that a depth jump consists of stepping off of a bench or object and upon hitting the ground immediately jumping back up. A shock jump consists of stepping off of a very high object and simply landing and absorbing the impact. Both of these exercises were also used for heights of around 3 feet or more.  It is true that for intense exercises like these an athlete needs to have strength levels sufficient to absorb the high forces without injury. Squatting 1.5 bodyweight would be a minimal number for these types of high intensity exercises.

The problem is, after plyometrics were brought to the USA and given their now common name, coaches began to lump all types of hopping, jumping, skipping, and bounding drills in with them.  In the process, many of the general strength recommendations such as being able to squat 1.5 x bodyweight given for "real" plyometrics ie.- depth jumps and shock drops, were also carried over to include all plyometric drills. Although having good strength levels is definitely a positive thing it is not necessary to squat 1.5 x your bodyweight to partake in light to moderate plyometric drills. These include just about all kinds of jumps, hops and bounds. In fact, pretty much everything except for high depth jumps and shock jumps. If you think about it, life and play are plyometric activities!
Next time you go by a playground have a look at the kids jumping around off and on playground equipment and such. They are putting a lot of stress on their bodies and surely not able to squat 1.5 x bodyweight yet how often do they get injured?  Not very often!

The bottom line is that improving your strength will allow you to get more out of the plyometric activities that you do and will also allow you to do more intense variations of them.  So, when it comes to plyometric activity, strength is definitely necessary and gives you an advantage.

Now you probably know more than 99% of all people when it comes to the science of the vertical jump. Comprehending power, force, and velocity is quite simple but lets do a quick review!

The vertical jump is a measure of power.

Power= Force x Velocity

Force- is increased by high-tension movements such as moderately heavy and heavy weight training

Velocity- is increased by lighter and faster weight training movements to improve the rate of force development, and by plyometric type movements to improve both rate of force development, and reactive strength.

To keep it simple all you need to know for a spectacular vertical jump is that you need:

1.   Force or Strength
2.   Rate of Force Development
3.   Plyometric or Reactive Strength