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Using Science to Determine Individuality

What if I told you that certain athletic characteristics can be genetic? Certain characteristics like speed, strength, power, and endurance are displayed differently among athletes. However, with the right training, you can alter your genetic codes that will allow you to express one characteristic more than the other.

There’s a really simple quote that basically sums up how we can manipulate our nervous system and genetic expressions:

Train fast to be fast

This quote could not be more true. If you think running 3+ miles a day and doing mostly slow, long-distance running is going to get you to the next level by getting in better “baseball shape” or to help you throw harder, here’s a news flash: you’re wrong.

Every year, I reflect upon the past year and ask myself what I can do differently. Today’s post is going to be from an evaluation standpoint. I came across a concept called the “Dynamic Strength Index” and it really caught my attention. Before we go over this concept, let’s go over some basic concepts first.

The Absolute Speed-Absolute Strength Continuum

In the past, I talked about this Speed-Strength continuum and how we can use it to develop athletes. This post sort of piggy-back’s off of this philosophy.

In short, all athletic skills are expressed along a continuum of speed and strength. How quickly we are able to express our strength is just as important as how much force we can produce. When you look at someone who is “athletic”, we can all agree that this individual expresses A LOT of force in a short amount of time.

In order to become more powerful/explosive, we first must develop force. We apply strength training to this equation because we are trying to increase our internal force output. With the use of external loads, we are able to accomplish this task over time. Once we are able to increase our internal output, that will dictate how much force we can express externally (jump higher, throw faster, move quicker, etc.).

The next part of this continuum is speed. You can be as strong as you want, but this will not directly result in becoming exponentially more powerful.

Think of an 18-wheel truck and a ferrari. Let’s say this truck can haul 1000 pounds with ease, and the ferrari can only haul 500 pounds. Which vehicle do you think can get from point A to point B in the quickest amount of time as possible? I’m going to say the ferrari. Because in relation to it’s own body type, it is able to express it’s maximal force in the shortest amount of time as possible. The 18-wheel truck is obviously very strong, but it takes a while for it to generate this maximal force.

The Strength Index/Explosive Strength Deficit

The ratio between an athlete’s ballistic peak force and their dynamic or isometric peak force is known as this deficit. The simplest way to measure this deficit is with a jump.

For the vertical jump, we first measure the athlete going through the entire loading phase and then jumping, like you would perform for any other jump. This number would be the ballistic peak force. The isometric peak force would be measured without the loading phase, so the athlete would start their jump at the bottom already loaded.

Dynamic Strength Index = Ballistic Peak Force / Isometric Peak Force

For example, my vertical jump is 34.5 inches. Let’s say my isometric peak force is 28 inches (non-counter movement jump).

DSI = 34.5/28 = 1.23

The DSI shows a reflection of the athlete’s ability to use their strength potential. If the DSI is a 1.0 or above, this demonstrates that the full athlete is able to use their full strength potential. A score of below 1.0 indicates that there is a slight deficit in the ability to use their peak force.

Here is a table taken from Science for Sport that gives a breakdown on training methods based on the DSI

ScoreDSI ScoreTraining Emphasis
Low< 0.6Ballistic Strength Training
Moderate0.6 – 0.8Concurrent Training (both ballistic and maximal strength)
High> 0.8Maximal Strength Training

All of this research has been taken on force plates and has shown to be a reliable source of determining the DSI. Most sport training facilities do not have a force plate, so how can we measure it?

If we are using the vertical jump, we can use the vertex. If we are using the broad jump, we can just use a broad jump mat, or markings on the ground to determine the distance that was performed.

However, if you really think about it without a force plate, this equation seems to be backwards. Of course the counter-movement will yield a greater jump height compared to without it. So, what do we do from here?

Now, let’s use the equation from the reverse:

**Dynamic Strength Index = Isometric Peak Force / Ballistic Peak Force

Athlete A: No CM Vertical = 28 inches

CMJ Vertical = 34.5 inches

Dynamic Strength Index = 0.81

Personally, I know that I am pretty good at overall force production, scaled to my own bodyweight, as well as rapidly producing that force.

Now let’s use the same equation with someone who has not-so-great numbers:

Athlete B: No CM Vertical = 19 inches

CMJ Vertical = 20 inches

Dynamic Strength Index = 0.95

You mean to tell me that Athlete B is a better athlete because this number is higher than Athlete A, even though both numbers are significantly higher?

Previous research has shown that the CMJ will yield results 20-30% greater than the non-counter movement jump. Now, here is the difference:

Athlete A = (34.5-28) / 28 = 0.23

Athlete B = (20-19) / 19 = 0.05

When we look at it from this perspective, we can agree that Athlete A is able to display a greater amount of rapid force production due to the rapid loading from the counter movement. Athlete B struggles to use the stretch-shortening cycle.

Try these theories out and let me know what you think!

Always learning,

Jarad Vollkommer, CSCS

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