G-Flight
(Find It Here http://www.exsurgo.us/gshop/)
The G-Flight is a portable, affordable, accurate jump height measuring device. It can measure jump height (time in air), ground contact time (GCT), and reactive strength index (RSI).
Validation (concurrent and construct)
Concurrent Validity
Concurrent validity is the validation process where the device in question (G-Flight) is compared to a gold standard device.
The Ezejump has been validated to the gold standard of jump height measurements (force plate). Thus, comparing the G-Flight to the EzeJump allows for concurrent validity to be tested.
After 40 Jumps comparing the G-Flight to the EzeJump, the r-value was 0.99. The average absolute difference between all jumps was 0.75 inches, the maximum difference out of the 40 jumps was 0.9 inches and the minimum difference was 0.57 inches.
Correlation between G-Flight and EzeJump
| Average Absolute Diff (Inch) | Max Diff( Inch) | Min Diff (Inch) |
| 0.7530511811 | 0.9921259843 | 0.5669291339 |
Force Plate Testing (Time In Air)
To get a better understanding of the G-Flight and the validation process, we were able to compare time in air measurements from a force plate to that of the G-Flight. Granted, the sample size was relatively small (16 total jumps). The findings were in line with the above EzeJump comparisons.
Correlation between G-Flight and Force Plate (Time In Air)
| Average Absolute Diff Inch | Max Diff Inch | Min Diff Inch |
| 0.9614512472 | 1.169291339 | 0.4015748031 |
Force Plate Testing (Impulse)
The G-Flight measures jump height via time in air, which due the nature of it will always lead to some human error (landing mechanics), but this is an error all time in air jump height measuring devices accept (contact mats, jump mats, phone apps etc..) Unless you are able to directly measure the impulse with a force plate, then it is more than likely the measuring device you are currently using has some level of built in error. Regardless, we were able to test the G-Flight jump height measurements (time in air) of both double leg and single leg jumps (23 total jumps) to jump height measured from a force plate (impulse).
Correlation between G-Flight and Force Plate (Impulse)
| Average Absolute Diff (Inch) | Max Diff (Inch) | Min Diff (Inch) |
| 0.7171448289 | 1.337868481 | -1.682539683 |
Construct Validity
Criterion validity refers to the process of making sure the device is measuring what you are trying to measure. Based on the physics and coding used in the G-Flight, the criterion validity is met
Systematic bias?
All jump heights measured on the G-Flight were lower (Average difference of 0.75 inches) than that of the EzeJump. This is due to the fact the sensor of the G-Flight sits ~ 1cm off the ground, which when accounted for, means the foot breaking the sensor will not take place until the foot is slightly already above the ground. Such error makes sense and is highlighted by the fact all metrics were on average 0.75 inches less than that of the EzeJump mat, which is contact based.
Relative Vs Magnitude
One of the questions we often get regarding presenting our error, is why do we present it in terms of magnitude (total inches) and not a relative values, like percentages? Well, the issue with percentages is that it is relative to the compared metric, which means if the compared metric is small, the %error will change, even if the magnitude of the error is the same.
for example, if the error of the G-flight is an average of 0.75 inches (lets just say 1 inch for the sake of simplicity) and we compare it to a “gold standard” measure, one can quickly see why percentage error might be misleading.
Take two jumps for example, one jump is 40 inches and the other is 10 inches. Now lets say the error for both jumps is 1 inch. If we use magnitude, the error for both jumps will still be 1 inch. However, if we use a relative metric, like a percentage error, then we get an error of 2.5% for the 40 inch jump and an error of 10% for the 10 inch jump, despite the fact the magnitude of error for both jumps is still equal at 1 inch.
Best Use
The G-Flight is most accurate when the pinky toe of the foot is roughly lined up with the sensors. Due to the fact the algorithm is based on when the sensor is broken, if the sensor is lined up with the back of the heel, it will start measuring jump height prior to the foot having actually left the ground. Landing is also of importance and a consistent landing position should be used, knees should not be tucked and the foot should be allowed to naturally strike the ground.
Pros
The G-Flight is an extremely affordable device. Compared to other jump height measuring devices on the market, it is nearly 1/4-1/10 of the price you would have to pay. At the same time, the G-Flight is much more portable and is easy to travel with. The compact size allows a coach to simply put it in their pocket or backpack for travel purposes. At the same time, despite the lower price point, when used properly, the measurements are very accurate compared to the other gold standard tests
Vision
The purpose behind the G-Flight is to provide all coaches and athletes with accurate, objective training metrics. Due to the price point of most other devices, it is not feasible to purchase jump devices in large quantities. However, due to the portability and affordability of the G-Flight, we see it being integrated into training and not just testing. We hope to see groups of athlete performing different jumping exercises and movements while using the G-Flight. At the same time, due to its accuracy, the G-Flight can also double as a testing tool. Thus, the G-Flight brings high performance sports technology to your pocket!
Where To Buy?
http://www.exsurgo.us/gshop/
G-Flight Extras
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