The Passive Spring

Storing and utilizing elastic energy is not only an intrinsic neuromuscular quality, but a skill. It requires the proper tensioning and timing of strong structural and contractile properties, which in turn allows them to store and realize the kinetic forces acting upon the body during the amortization phase of the jump. In other words, proper skill and strength allows you to act more like a bouncy ball when you hit the ground and less like a sack of potatoes.

Image 1

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Using Tendo Units To Measure Jump Height (Physics Cheat Sheet)

Jump Height and Peak Velocity of a movement are very strongly correlated to one another. Peak velocity at the end of the push-off phase determines your jump height (Impulse – Momentum relationship). Technically speaking, you actually reach peak velocity right before you leave the ground, which means the highest peak velocity that occurs in a vertical jumping movement, say a jump squat, doesn’t actually occur at push off, instead right before. Because of this, technically speaking peak velocity will not give you a 100% accurate measure of vertical jump height. However, neither will a just jump mat or most any field testing tool that doesn’t directly calculate impulse. Which means in this case, reliability is very important and from my own personal work, using peak velocity is quite reliable (there are a couple of studies supporting me too).


Remember, peak velocity is going to be used a metric to determine an object’s displacement, in this case a jump height. One issue with peak velocity is that, well, it is peak velocity… As coach knowing peak velocity is cool, but kind of useless unless you have a calculator on hand during a training set… which I really hope you don’t. So, what good is peak velocity?

Well, peak velocity is great, especially for a nerd like myself. I like physics and I like numbers, which means I decided to put together a peak velocity “Cheat Sheet”.

Below is a graph of peak velocity (in this case representing push off velocity) and inches. Again, you can see that its kind of a mess and for the most part, useless in the weight room. However, it does give you quick snapshot of how jump height and peak velocity are not linearly related, which means you cannot just take peak velocity and assume an increase means one to one, linear increase in jump height. 

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Moment Arms and Exercise Progression (physics)

Progressive Overload

Exercise progression plays a vital role in all strength training programs. The concept of “progressive overload” hinges on this very concept of. As we all know, without some type of progression the athlete’s development will most likely stagnant and possibly begin to decline. This is why we increase weight in exercises. The weight adds overload in a progressive fashion. However, weight is not the only way we can manipulate our training to increase the demands of the body.

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Relax/Drop-Catch Exercises

I have heard these exercises called a couple of different names (drop catch/relax catch) and to be quite honest,  I think either one works. I am not quite sure who came up them, but I have seen them in being used by many successful coaches. For the sake of consistency, in this article I am going to refer to them as drop-catch exercises

What Are They?

Drop-catch exercises involve starting at the top of position of the movement, letting yourself relax and then catching your self at the bottom before exploding back up. I believe Cal Dietz and Joel Smith have written articles on how to perform these. Each person probably has their own specific method of teaching the movements, (some prefer to actively pull yourself to the bottom while some say just relax and fall) and I assume you can find their teachings at their respective websites. However, this article isn’t made to talk about the technique and form of the movement, but instead the principles behind the movement.

Below is an example of a drop catch performed by AFL

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Post Activation Potentiation: The Physiology and Physics

Human movement/performance is a summation of many different sciences. In order to optimize training we need to understand how these sciences are intertwined. The best way to illustrate this idea is by looking at post activation potentiation (PAP) and how the acute changes in physiology will affect the physics of movement.

PAP is the process of bringing the body to its highest functioning state. Typically, post activation potentiation is done by using some sort of maximal intent movement, over a short range of motion, to facilitate the performance of another movement.

Two window model of PAP (Image 1)

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Physics (Peak Velocity)


Peak Velocity can be used to determine whether an olympic lift is missed due to bar height or technical error. However, you first have to understand what peak velocity is.

Peak velocity is a specific point in the movement at which velocity of the measured object (center of mass, barbell, projectile…) is at its highest. Depending on the type of movement being performed, peak velocity will occur at different regions within the movement.

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Physics (Sprint Velocity)

Velocity is the change in distance over the time it takes to for the change in distance to occur. For example if I were to start running from stationary position (Initial Distance ‘Di’) and run 40 yards (Final Distance ‘Df’) in 4.4 seconds my average velocity for the entire run would be the change in distance (40yards) divided by the time it took to travel that distance (4.4 seconds).

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