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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Rate of Force Development (Early versus Late)

Rate of force development (RFD) can be broken down into two stages. There is an early stage rate of force development and a late stage rate of force development.  Early stage RFD is typically measured from 0-100 ms while late stage RFD is anything after.

Importance of Early Stage RFD

Sporting movements are often required to be fast, reactive movements that occur over a small amplitude. For example a large countermovement jump can take between 500-1000ms, while a squat jump with no countermovement may take around 300 to 430ms (1). In sport, movement amplitude is going to be much more similar to that of a squat jump (zero to minimal countermovement) than to that of a large CMJ. At the same time, sprinting ground contact times can last as short as 100ms. With this in mind, it is easy to see how early RFD may play an important role in sporting movement, especially those covering a small amplitude over a short period of time (ranging from 100-430ms).

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Muscle Slack and High Velocity Training: An Integrative Approach

Velocity Deficient

 

The idea of measuring and training for velocity deficiencies has become popular since the recent studies of JB Morin and colleagues. In one of their studies, they examined several different subjects and based on their profiling methods, determined whether or not the individuals had a force-velocity profile that was either velocity deficient or force deficient. Once the deficiency was determined, the subjects were trained using specific methods emphasizing the velocity component of the movement (slow velocity for max force and fast velocity for speed of movement). After the study’s training cycle, J.B Morin and colleagues were able to show that the specific training methods, either slow or fast, improved vertical jump performance and overall balance of the subjects’ force velocity profiles.

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Velocity Based Training Methods

Velocity based training (VBT) is an awesome tool. It can be used in an assortment of ways to better your training. However, because of its diversity, it can cause some confusion as to what methods should be used and how to use them. Below will be several examples of how to utilize different velocity based training methods in your program

Using it as a percentage of one rep max

Velocity based training can be used in conjunction with the traditional training method of using a percentage of one rep max. This is probably one of the most common way it is used. In this method, velocity is used to auto-regulate training. Instead of only assigning a percentage of one rep max, you will assign a velocity that correlates with the percentage of one rep max. This way, the athlete will focus on lifting as much weight as possible at the desired velocity. This will take into account daily fluctuations in strength, thus making it auto-regulatory.

Velocity and %1rm relationship (1)

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