The Power Of Jump Metrics

The rehabilitation process is a very complex, multidimensional endeavor. It is extremely hard to determined when an athlete is truly ready to return to perform at their highest level. Despite the fact that psychologically they may be more than ready to return, their body may not permit it, or visa versa. There is no “best answer” to this problem. It is much more of a sliding scale (kind of and maybe) than it is binary (ready or not).

One aspect of return to play that is often overlooked in the sports performance world is the standardization of measurement. For example, strength coaches may use a series of physical performance tests to determine an athlete’s physical profile, while on the other hand an athletic trainer or a physical therapist may use a separate set of metrics. Now, this isn’t to say one metric is superior to the other, it is simply to point out that lack of standardization can make comparing before and after profiles quite difficult.

To solve this problem, open communication is the quickest answer. How many physical therapists (PTs) and athletic training (ATs) know an athlete’s max squat, 40 yard dash time, single leg vertical jump or yo-yo score prior to the injury? My guess not many… If the performance coach, who is responsible for the development of well, performance puts value into these metrics as an indicator success, then it might be wise for the athletic trainers and physical therapist to value these metrics as well. Now, the same can be said for the strength coach as well. If the ATs and PTs value certain metrics, maybe the performance coach should understand the significance of these metrics. We can sit here and debate all day as to which metrics we should value over others, however at the end of the day, it comes down to utility. Are these metrics easy to obtain and do we have the equipment for it? If so, how easy is it to use this equipment and how applicable is it in our given setting?

One of the simplest, cost effective and least invasive tests an athlete can perform is a jump test. It takes up minimal space, there is one piece of required equipment and it can tell you quite a bit about an athlete, especially if you know what you are looking for. Now, there are a multitude of jump tests you can perform and each one gives you some different insights. From asymmetry testing to two foot maximal vertical jump measurement, a simple jump device can yield some useful metrics. For this reason, I am making the case that jump devices can be and should be used in the S&C setting as well as the rehabilitation setting. Such a small addition can allow for better communication and more standardization across tests.


This is one of the exact reasons why we developed the G-Flight. One of the biggest issues with current jump devices on the market is the fact they take up a good amount of space. In a facility like a training room, space is precious and cumbersome items get casted away to a closet never to be seen again. Thankfully, the G-Flight is not like other devices. It is a wireless, portable jump device that provides immediate feedback to the practitioner. It records reactive strength index, ground contact time and jump height.

Here is what the final version of the G-Flight will look like! It will be wireless and fit in the palm of your hand! It will display jump height in inches and centimeters, rsi and ground contact times! If you are interested in purchasing it, check out the link in my bio. For more info, shoot me a message! . Also wanted to use this post as a chance to thank everyone for all of the support. and I have set out on a mission to bring a new age of affordable and portable sports tech. Made by coaches for coaches, these devices are designed to be used day in and day not. We couldn't be where we are now without everyone's input, patience and willingness to hop on board. -Max and Greg @arcthirtyfour . . #trackandfield #sports performance #exercisescience #training #train #science #strengthandconditioning #strength #strengthtraining #strengthtrain #train #lift #weights #conjugate #powerlifting #weightlifting #cscs #exercisephysiology #squat #bench #deadlift #fitness #strengthcoach #strongbyscience #gflight

A post shared by Max Schmarzo (ATC/CSCS/MS) (@strong_by_science) on


For more info on the G-Flight CLICK HERE

What do jump metrics mean?


Countermovement Jump (with arms)

The countermovement jump with arms is the most traditional test. The goal of the test is to see how high an athlete get off the ground with the use of their entire body

Countermovement Jump (no arms)

The countermovement jump performed without arms is test typically used to see raw jumping ability of the lower legs. Because the arm swing is removed, the “skill” aspect of the arm swing will not influence the jump height.

The ratio between cmj with arms and without arms can be used to measure the influence of “skill”

Squat Jump

The squat jump is done from a static position, starting at the transition point between eccentric and concentric movement. The movement is done with their hands on their hips. Due to the shorter contraction time, squat jump is typically looked at as a rough measure of rate of force development

The ratio between CMJ without arms and SJ is typically used to measure elastic contribution and rate of force development abilities 

Single foot jumps

Single foot jumps can be used to monitor jumping asymmetries. Differences between left and right foot can be used to evaluate possible “red flags”

Ground Contact Times

Ground contact time is the time spent on the ground during a jump. This is only used during a continuous hop. For the most part, when performing plyometrics, fast ground contact times are >250millesconds

Reactive Strength Index

Reactive strength index is a composite score of ground contact time and jump height. The shorter the ground contact time and the higher you jump, the better the score. It is typically used during a repeat hop test or a depth jump

Fatigue Monitoring and Work Capacity


Decrement of ground contact times

A number of jumps over a given period of time can be performed and the decrement of ground contact times can be evaluated. This may give some insights into the SSC properties of the athlete and shed light on how they compensate under fatigue

Decrement of jump height

A number of jumps over a given period of time can be performed and the decrement of jump can be evaluated. This may give some insights into the SSC properties of the athlete and shed light on how they compensate under fatigue

Power Capacity 

The coach can assign a specific % drop off in jump height and perform as many jumps as possible within that given range. For example, a practitioner may want to see how many jumps they can perform at roughly 10% of their best jump height. This will shed some light on s their power capacity



Jump height

Jump height auto-regulation can be performed. Instead of assigning a specific number of jumps, a practitioner can assign a specific reduction in jump height. This will allow for a better understanding of fatigue

Ground Contact

Ground contact auto-regulation can be performed. Instead of assigning a specific number of jumps, a practitioner can assign a specific reduction in ground contact time over a series of jumps. This will allow for a better understanding of fatigue

Daily Readiness

Jump heights can be tracked over time to understand the level of readiness for that given day. It can be used to collect data that can immediately impact what kind of training session one may perform.


A simple jump device can be a powerful tool when used properly. Granted, it will never answer all of your questions, but it can be a piece the puzzle

Leave a Reply

Your email address will not be published. Required fields are marked *