Nearly every program in America tests the vertical jump. Why?

The usual answer is that it is used to see how explosive and/or powerful each player is. The person who has the highest vertical is going to be the most explosive. The person who has the lowest vertical, on the other hand, is going to be the least explosive. If an athlete’s vertical is increasing every training cycle, then he is getting more explosive. Conversely, if it is staying the same or decreasing, the athlete is losing his ability to produce power.

That sounds so simple, doesn’t it? What a great way to track training...

However, I am going to be the bearer of bad news. It’s not that simple. The vertical jump doesn’t give you power. That's right. Although it does give you some useful data to determine power, it does not give you power. If you are monitoring vertical jump to determine power, you’re a bit off. Take, for instance, a player who has moved to a bigger position. Let's say a safety became a linebacker. Then, he switched to a defensive end and then to a defensive tackle, and his vertical jump changed at every position. Did he really become less powerful over time?

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When someone mentions how many watts of power an athlete is putting out, a strength coach often thinks of a force plate (which is very expensive). On the other hand, some coaches may hook each athlete up to the Tendo, enter his bodyweight, and then have him do a vertical jump. The Tendo or myotest, both of which use velocity and bodyweight to calculate power, are accurate and less expensive than a force plate...but they still cost between $500 and $1,500.

However, there is something even simpler than the Tendo and Myotest, and it costs much less. Realizing that gravity is a constant, and that would mean that time and velocity would have to be the same for each jump height, velocity can be gathered from the jump and used in combination with bodyweight to determine peak power in watts. Luckily, several researchers have even used a force plate to formulate equations for those of us who can’t afford all of the high-tech and fancy gizmos like the Tendo or force plate. In fact, one such researcher is Dr. Steve Sayers, currently at the University of Missouri. While at UMass, however, he developed what is known as the Sayers Power Equation. There is one downside to the use of this equation, uses the metric system. Damn scientists and their need for international regulation. Therefore, jump height will need to be changed to centimeters (jump height multiplied by 2.54), and bodyweight will need to be converted to kilograms (bodyweight in pounds divided by 2.2). Here is the magic equation:

PAPw (Watts) = 60.7 x jump height(cm) + 45.3 x body mass(kg) – 2055

For those who track their data and keep it in some sort of format (usually excel), the determination of peak power in watts is the addition of one cell, but the information it gives you is priceless. You can now compare apples to apples. Who is the most powerful person on the team? When someone's bodyweight changes, is he actually producing more power? Is his ability to produce increasing? Is it decreasing? Does a need exist to improve rate of force development? At this point, more can be done.

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Allometric Scaling

The human body does not exist in the same proportions from smaller to larger. Skeletons do not grow in proportion to a person's size, nor do they possess contractile properties. Therefore, when examining relative strength, a true comparison can’t be made due to the incongruity of the size/weight of skeletons. With this is mind, allometric scaling has been found to be effective in comparing relative strength across different groups. When using allometric scaling to compare an entire football team, you will regain a bell curve (where it had disappeared among multiple peaks in terms of a standard relative power). In essence, you get a watts/kg that is congruent across the entire team—from safeties to offensive linemen. Also, realize that it is tough to compare vertical jumps among various schools that use different measurement systems. The numbers will be slightly different, so it will even be tough to compare the averages. For instance, the vertec only measures in half inches. However, a switch mat will measure down to the tenths of an inch. Thus, the average could be thrown off because the vertec measured group could be at a .4-inch deficit with various athletes throughout the team.

It must be understood that if you are looking at longitudinal data, the same type of vertical jump must be taken every time. There are several different ways to measure someone's vertical jump: force plate, switch mat, vertec, jump height minus reach on the wall, etc. Thus, comparisons between measurement systems may give altered data, leading to altered power results. If one method is used consistently, the changes in values as found from that method will give the practitioner an understanding as to the effectiveness of his training program.

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Recently, there have been some people talking about how the vertical jump is a skill rather than a true power measurement. In some respects, this is true. The height of the vertical jump is dependent upon the speed of the center of mass upon takeoff. Athletes, in an effort to get the highest possible score, will find a way to enable them to jump as high as possible. This has led many people to rely solely on strength for power production. Therefore, they take long, slow windups (increasing squat depths) in order to have a longer acceleration phase before takeoff. On the other hand, those who rely on neural capabilities tend to have very minimal knee bend and hip bend before the jump. The key here is that while it is true that the method of vertical jumping has an impact on the results, it is also true that the athlete will stay with that style. If he is now jumping higher by using whichever chosen method of vertical jump, then his is producing more power. This can be likened to the “bathroom scale theory.” Bathroom scales are not always completely accurate when compared to doctors' scales or the scales at a meet, but they can tell you if you've lost or gained weight. While very crude, it is a cheap/free method to see if you've improved your power.

Now, before this looks to become an “end-all, be-all” to all issues related to performance, realize that this is just the beginning. There are many things for which power can be used, and it can be dealt with in simple calculations in order to give even more information and clarification for you in your search. And just like the song says, “We've only just begun…”  This is no sprint or race. This is a journey, and it is steadily taken one step at a time.