Although the popularity of, and excitement over, force plates and contact grids is palpable, the Just Jump contact mat still has plenty of value. Coaches who have the Just Jump system or don’t have a budget for higher-priced equipment can still get a lot of value from the contact mat.
This overview covers what the Just Jump system can and can’t do. In addition to the pros and cons of the equipment, I give some pointers for using the contact mat and suggest what population to best use it for. No matter what jump assessment tool you rely on, you will benefit from the information provided in this article.
About the Just Jump System
The Just Jump testing system is a contact mat that collects air and contact times. Most coaches that use the testing device measure air time when testing vertical jumps. You can also use the equipment for sprint and shuttle tests, but for most coaches, it’s a handy tool for estimating vertical jumps.The #JustJump tests quickly, and helps us make straightforward decisions for our younger athletes, @ShaneDavs. Click To Tweet
The Just Jump is not a force plate; it’s a mat that knows when an athlete is on it and when an athlete is in the air, but it’s still useful for coaches who want to see changes in their training program. At our facility, we have used the Just Jump System for years to help drive straightforward decisions with younger athletes, and the convenience of quick testing is a perfect fit for us.
For the last 20 years, the Just Jump system has been researched for validity and reliability in testing jumps compared to a gold standard. The results are clear—the product is useful for estimating jumping ability, but it’s not the same as a force plate.
Recently, sport scientists conjured up a correction formula to improve the data, and that is especially useful to determine a true jump score. I care about improvement and watch technique carefully to ensure that improvement is coming from the legs getting more explosive, not the athlete cheating by landing with a deep squat. At our facility, we allow a soft landing, but it’s “soft and shallow,” not low and hard.
What the Just Jump Can and Can’t Do
When you buy a system, it’s for ease of use and estimating change in a training program. We use both a contact grid and a force plate with our athletes now, but when we have a mob of athletes and little time for testing, we will use the Just Jump. We also have a Vertec because we want athletes to be familiar with jumping up and reaching, not just performing the strict tests recommended by the scientists.When we have a mob of athletes and little time for testing, we use the Just Jump, says @ShaneDavs. Click To Tweet
You can calculate the power and forces from a contact mat, but the device doesn’t measure those scores directly. Additionally, you can’t acquire the differences between right and left legs, so if you are doing rehab like us, that will be a major drawback. The Just Jump is also not a tool for horizontal jumping and bounding, and the system has a set amount of jumps it can collect with canned tests such as the 4-jump test. Lastly, the system can’t detect if an athlete is rolling, rocking, or dipping when doing a non-countermovement jump.
A great coach will see it if an athlete is not strict, but automated sensors do help and that’s why force plates are great for detecting a quiet phase. When training in a group, athletes watching strict techniques is helpful not only for jump testing, but any training that requires a pause or isometric contraction.
NFL Combine Vertical Testing
Conventional vertical jump testing is not as valid as jumping with hands on hips or hands holding a rod, but we still like to look at those numbers because they’re more real to athletes trying to rob a home run in baseball or block a shot in basketball. We still do jump tests with more “lab-like” mechanics, but to connect an athlete to testing when they are young, it is important to include a vertical jump with arms. With our Combine athletes, we test using a Vertec and Just Jump at the same time, as it adds a layer of confidence in the training data and prepares athletes for the actual testing they will do on Pro Day.
Video 1. Vertical jumping with arms is a standard test in the NFL, and other organizations using this form of test often include a Vertec. Because the movement has higher variability from the torso and arms, the test is not as reliable as those without arm contribution, but is good to add to a jump testing battery.
We have had plenty of athletes go on to play Division I football, hockey, and volleyball, and some of them have gone to programs that test with force plates. We know that the tests will show data that is very hard to satisfy an uneducated ego, but after testing with different jumping styles, they know that without the arms and a countermovement, their heights will be lower. As with electronic timing and hand times, you should educate the athlete on the differences because they always want the better score to represent what they can do. We are upfront in explaining the differences in technology so nothing is fudged or inflated.
Elastic Rebound Testing
The 4-jump test is popular because it is fast and indicates if an athlete has a good bounce; meaning they are able to use stored energy from their legs. We can tell a lot from this test, but it requires some practice for athletes. We used the 4-jump test to spitball an athlete’s ability to perform plyometric motions, but the test can’t do much more than estimate rebound jump height.
Scores on the 4-jump test will be lower than a contact grid because the mat size is smaller, forcing an athlete to focus on steering just as much as maximal jumping. We like having a restricted space, as it demonstrates a standard form of body control.
Young athletes tend to be a great fit with the 4-jump test, mainly because they are less skilled and less elastic. The power-to-weight ratio factor does make interpretation of the information difficult, as some athletes tend to get bigger and stronger before their ability to store and use elastic energy develops. We like testing more frequently to ensure we are vigilant with the long-term development process, because speed and eccentric abilities are so important. When we see a big discrepancy between the concentric and eccentric scores on the kMeter and with the jump tests, we know that some athletes need special attention paid to elastic development.
The eccentric utilization ratio (EUR) is a solid metric for identifying changes in a season, or whether an athlete needs more plyometrics in their training program. Like the rest of the jump numbers, this calculation is more of a flag than anything else. If we see poor absolute numbers we don’t worry too much about what the athlete needs, as poor power is obvious, but for athletes who have trained for a while, we want to know that both starting speed and deceleration abilities are developed. Athletes with poor eccentric abilities that are fast tend to be talented but underdeveloped. We close the gap by making sure the EUR is solid after putting in the work over a few months.
Universal Jump Tests
You can perform Bosco tests, specifically jumping without arms with and without countermovement, with the Just Jump system. In order to get the most out of the test, the athlete needs to land with a nearly straight leg because the air time starts when the feet no longer apply weight on the mat, and that is near toe-off. When landing, an athlete has to look very similar to the way they looked when they started the jump, otherwise the scores are going to be artificially inflated.Field-ready reliability is the key to the Just Jump mat, and we like to see real progress in inches, says @ShaneDavs. Click To Tweet
Field-ready reliability is the key to the Just Jump mat, and we like to see real progress in inches, not fractions of an inch. If you want laser precision, actual force is needed, not jump height. Still, a firm protocol and tough coaching will ensure that contact mat numbers are solid enough to make programming decisions. As long as a coach doesn’t cave in, a contact mat like the Just Jump is enough to see obvious development; when it becomes too close to call, other tests are needed.
Test numbers are worthless if you have no time to train, because you can’t do anything to intervene, says @ShaneDavs. Click To Tweet
What is useful with contact mat jumping is speed of testing. Wearables are fine with small groups and unlimited time, but with larger groups like entire teams, it breaks down. With three or four stations, an entire team can test in a few minutes, and this is necessary for in-season training. Some teams have less than an hour to fully train—sometimes less than 30 minutes—so data collection that takes long can defeat the purpose of capturing it in the first place. If you don’t have time to train because you are testing, then the numbers are meaningless because you can’t do anything to intervene.
Reactive Jumping with the Chip
You can assess for Reactive Strength Index (RSI) with force plates and contact grids, but you can also enhance the Just Jump with an external chip that is roughly $70 and needs to be specially ordered. If you are trying to get the RSI, you can use a box about 12-18 inches high and place a hurdle on the other side of the mat. The hurdle encourages an athlete to be both reactive and propulsive, as the small barrier cues the athlete to think about projection and speed off the mat.
We like to see 0.2 seconds or faster, and understand the precision doesn’t need to be perfect to be useful. As long as the athlete performs the task effectively, the contact time is useful. Landing on the mat instead of on the ground beyond the hurdle can get air time, but we like using the hurdles because the movement is better and the athletes look athletic and elastic.
Due to the sensitivity of jump testing, fatigue is difficult to discern with jump tests alone, especially when athletes are not motivated to perform their best when the numbers are not part of a reward process. Like screening, fatigue monitoring requires more than just one number alone to determine risk, so we think asking how athletes feel when the numbers are clearly compromised is better than just assuming jump tests are representative of their readiness to lift or sprint.
SimpliFaster has published several articles on jump testing and jump training, and a few buyer’s guides on contact grids and force plates are also available. The most important factors for investing in testing are the time involved and the information you receive, not the cost of the equipment.The most important reason to invest in testing is the info you receive, not the equipment’s cost, says @ShaneDavs. Click To Tweet
Jump testing or any type of testing requires a plan for what to do when you receive the information, and simple testing and a decision tree is a great start. The Just Jump system is a great entry tool for coaches wanting to get data that is both practical and reliable, but you need to know what to do with the data and what the limits of the system are.
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