To begin, understand that the vertical jump is simply just a measurement of power.
WHAT IS POWER?
Power can be determined by a simple equation:
Power = Force x Velocity
To break it down just realize that power and explosive strength simply mean the ability to apply a given amount of force over a period of time. The more force you can put out and the faster you can apply that force, the higher your power output will be.
In order to understand how to improve power, it helps if we to know how to manipulate each component of the equation, force and velocity.
When we most often think of force, the word strength comes to mind. In mathematical terms Force = Mass x Acceleration.
Simply put, if you move a larger or heavier mass or accelerate it more rapidly from point A to point B, you will increase force and subsequently, power output. For our purposes however, no need to get overly technical! It's easier to think of the force part of the equation as your maximal level of strength.
Velocity- is the speed of movement.
Simply put, the greater the force or velocity, the higher the power output.
It's really not much more complicated then that. However, before we move on, I'd like to define some key terms that are all interconnected in the quest to improve power and jumping ability. You'll see some of these terms periodically throughout this book.
Limit Strength- is simply the maximum force you can voluntarily apply. Maximum force is typically measured in the weight room with powerlifting being a classic example of a sport that measures maximum force. Actually a better name for that sport would be force-lifting or strength lifting. Because of the slower velocities inherent when lifting a maximal load, powerlifters actually generate less power then athletes in many other sports. Other then arm wrestling and maybe tug of war, powerlifting is also about the only sport where maximum force is measured.
Absolute strength- is the maximum force one is potentially capable of applying. As you will learn later it is rare to see our strength potentials fully realized.
Relative strength- is the strength per pound of bodyweight
Rate of force development- Is the speed at which you can develop force. Starting strength- influences rate of force development and is the ability to instantaneously turn on as many muscle fibers as possible when movement begins to take place.
Reactive strength- is also known as elastic strength, reversal strength or plyometric strength. This is the ability to gather and utilize reflexive force during a movement when switching from an eccentric (negative) contraction to a concentric (positive) contraction.
As stated, power-lifting, arm wrestling, and tug-of-war are some sports that measure this. In practically every other athletic event, there isn't enough time to allow true maximum force to be developed. So in this case you see that athlete "A" reaches a higher peak force and he squats more weight, 400 lbs vs 300 lbs, yet if you look at the 3rd row, the amount of force he can put out in.2 seconds, which is the same amount of time it takes to complete a vertical jump, - Athlete A's force output is lower then that of athlete B, so he develops force slower. Therefore, athlete A is going to be able to squat more than athlete B, but athlete B is going to smoke athlete A in a vertical jump test. Here's why:
In the maximum squat or maximum force test, the athlete has plenty of time to generate peak force. It takes roughly .4-.7 seconds to develop peak force. On the other hand, movements like the vertical jump inherently occur very quickly, around .2 seconds. So, how much force you can put out in a short period of time is going to determine performance.
Don't get too carried away with this just yet though. Although being able to apply force rapidly is a very useful characteristic, you still need to have enough potential force to tap into for anything to happen. The 6'3", 200 lb guy with a max squat of 100 lbs is not going to be dunking any time soon, even if he can apply all that force very rapidly.
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