How to Enhance Power with Jump Profiling
Have you ever observed a child’s growth from a baby to a two-year-old? A naturally developing baby goes through various stages of mobilization. First, they wiggle and roll around on the floor to get from point A to point B. Then they discover how to get up on their hands and knees and crawl. This is a watershed moment for any parent as they can never assume again that their child will be on the spot they left them. Then every child’s monumental moment – taking the first step. The funny thing is that it might take the average child an entire year to take that first step, and then within a week that same child is running and jumping…and jumping… and jumping.
When it comes to athletes, jump testing is one of the most common assessments of an athlete’s explosive ability. Performing variations of jump tests are relatively easy and require limited energy output from the athlete. This is an important consideration as you don’t want to detract from the player’s ability to give their best effort.
Keeping track of a player’s jumping ability is another piece of information that helps chart progress. With this test, we want to track fatigue and see if the player is stronger during the season. To keep track of a player’s improvement, we use a simple formula: Power + Force Acceleration (F=MA force is mass time acceleration). If you’re moving your body weight faster or higher, you know your power is going up. Power is only able to increase with a surge in either acceleration or in this case, mass.
Jump testing helps trainers and coaches rate an athlete’s progress in the long-term power development of a training program. It also helps show an athlete that the training program is working based on the different jump tests’ measurable results. Conversely, if the jump tests level out or regress, you and the athlete know you need to modify something. As a side note, when you’re posting your players’ results, the competitive nature of the athletes comes out, and players will concentrate more to out jump their teammates.
As we said, at its core, jump testing measures the explosive ability of an athlete. Being able to jump high might not indicate any other athletic ability. The test doesn’t necessarily indicate technical ability in a particular sport, but it shows the person has the physical potential to perform at a certain level. Jump testing is looking more at an athlete’s power than strength. Although strength is an important quality that will in some ways dictate power output, it is not the only quality. With jump testing, we are looking more at the power side of the force equation.
An athlete’s jumping ability is also a valuable tool to determine if they’re ready to return after an injury. When you have a baseline to measure against, you can evaluate to see if it’s close to their normal score. If they don’t have that explosive ability yet, then it’s probably not the time to return that player to full-time practice sessions or playing in a game. Just watching how a player is jumping is key here. You want to know if rehab is complete, but also that strength levels and motor control are where they need to be before working the player back into a full regimen of workouts and practices.
With the variations of tests, you can also determine if one leg might be weaker than another and develop training regimes based on that information. There is a functional asymmetry between both limbs, and you can develop an appropriate training plan if you see a marked difference in power between the two legs.
For the jump tests to give you the data you want, you need the correct equipment to do the measurements. The first type we are going to talk about is force plates. As the name suggests, they precisely measure the force applied on the contact surface by strain sensors. In its simplest form, an athlete jumps into the air off the plate and lands back on it. The equipment measures the force applied to the ground to create an upward movement of the body. Force plates can also measure the comparative strength of the right and left leg. The information you obtain from force plates can help performance coaches and medical staff arrive at important decisions on the rehab progress of an injured athlete.
Force plates are at the high end regarding the price for equipment. They tend to be more applicable for elite athletes due to the price tag and the importance of the athlete being able to replicate their jump motion each time. A deviation in the mechanics of the jump will create vastly different metrics, and these can be very important to understand. However, if the mechanics change from jump to jump simply because the athlete is a novice and has a low technical skill level, then the information put forth by the force plate won’t be accurate. This is an important consideration as any variation in the takeoff or landing is going to skew the measurement. While this is true with any method you use to test jumps, it is especially important with force plates. You want a player’s technique when testing to be as identical as possible from one jump to another.
Contact mats are a more inexpensive solution and used by high schools, colleges, and even at the professional level. Contact mats use a simple equation using displacement of mat contact to determine jump heights. The information isn’t as accurate as with force plates since force isn’t one of the measurements here. However, they do provide data on contact time, or how long an athlete is in contact with the ground in jump tests such as the drop jump, and this particular metric can provide valuable insight into how an athlete produces power. However, a player can alter the results by changing how they land. A performance coach needs to closely supervise jump tests on mats to make sure athletes are performing properly. After all, competitive athletes are going to try to squeeze out any advantage they can if it means a higher score over their teammates. Still, contact mats give you results you can use, and the price fits most budgets.
A simple device for testing vertical jump height is the Vertec. It consists of a base with an adjustable upright supporting colored vanes spaced 1/2 ” apart that rotate when touched for easy measurement. The test takes some skill and timing for an athlete to jump and reach to their maximum height, but it gives you an accurate indication of a player’s ability to do that if they perform the jump properly. Another benefit of this tool is that it can easily be used to measure the height of “approach jumps,” which are common and an important test in basketball and volleyball.
As with all training aspects we talk about in this book, there are different types and makes of equipment to measure jumps. You should have an idea of what they want to measure in a player’s jumping ability. You need to research what fits your program and budget to choose the right equipment.
Aside from testing for pure height and reach in a jump, one of the metrics you want from a jump test is an athlete’s Reactive Strength Index. This metric illustrates how a player produces power. An athlete can spend a long time on the ground to conserve muscle motor units and produce concentric muscular force, or they can rely on the stretch-shortening cycle to produce power via stored elastic energy. Optimally, they will do both to make the best use of the combination.
According to scienceforsports.com, there are three common methods to calculate the performance of the RSI test. These are:
- Method 1: RSI = Jump Height / Ground Contact Time
- Method 2: RSI = Flight Time / Ground Contact Time
- Method 3: RSI = Jump Height / Time to Take-off
“Jump height is an estimate of the height change in the athlete’s center of mass. Jump height is best measured using the velocity data from a force platform. This can be calculated using the following formula: Jump Height = 9.81 * (flight time)2 / 8
Flight time is quite simply the total time the athlete is in the air during a jump – from when they break contact with the floor, to when they first touch down upon landing. This is often measured using a jump/ contact mat. However, results can be easily influenced by body position during take-off and landing. For example, if an athlete bends their legs during flight, this can alter the results and affect the accuracy of the test.
Time to take-off includes the eccentric and concentric phases of the stretch-shortening cycle.”
Though both jump height and flight time can be measured directly and accurately, numerous professionals prefer to use flight time as opposed to jumping height because it’s easier to measure and less time-consuming. It makes little difference which calculation you use since jump height and flight time are strongly correlated as both are a straight mathematical derivation.
If using a force plate, it is better to use jump height based on ground reaction forces as this has been suggested to provide a more valid RSI measure. If you don’t have a force plate, then using flight time calculated from a contact mat also works well and is often used in research.
There are different types of jumps you can have your players perform. Each variation provides a different context. Taken collectively, you will have a more nuanced understanding of a player’s strengths and weaknesses regarding their force application strategy than just one variation on its own. The countermovement (CMJ) jump is the typical jump to determine explosive power. Because of the arm swing, the CMJ has an upper body element. It also uses some degree of the stretch-shortening cycle since the athlete “counters” the downward movement of the initial phase of the jump. This type of jump is also referred to as a “long contact” or “long stretch shortening” jump, vs. a drop jump which has a much quicker “counter” movement and is often referred to as a short contact or short stretch-shortening cycle jump.
The non-counter movement (NCM) jump eliminates the stretch-shortening cycle. Athletes keep their hands on the hips for the jump, which cuts down on the upper body movement. Athletes also start out with the knees bent and the thighs parallel to the floor, from the position they jump from. The NCM provides information on an athlete’s ability to produce force only from a concentric muscular action.
A single leg vertical jump provides a strength coach or performance coach with data on unilateral power development and force application, as well as left/right asymmetries. Almost all team sports are unilateral in nature. Determining the ability of each limb to produce force and create movement is important. If there is a huge difference in the force production and/or force absorption between each leg, the risk of injury increases. By assessing single leg vertical jump using a “hands on hips” technique to focus on unilateral lower body power, we can determine if any significant injury potential and/or performance detriment exists. You want to have a bilateral leg landing to avoid the risk of injury. This also assures that the jump is of maximal nature.
An even more in-depth layer of analysis would be to utilize the force plate to measure and assess the landing ability and characteristics of each limb when landing unilaterally. Aside from using the “eye test” or use of video to determine landing strategy, the eccentric loading data from a force plate can potentially identify neuromuscular asymmetries and help prevent injuries.
The drop jump has the athlete stand on an elevated surface, such as a bench. The athlete begins with hands on hips, steps off the elevated surface, allowing themselves to fall toward the ground. Upon landing, the athlete attempts to “rebound” back up in the air as high and as quickly as possible. This jump variation is primarily dependent on the stretch-shortening cycle. The tendons and ligaments must rapidly absorb the kinetic energy from the descent, and quickly use that to create a force in the opposite direction. This jump will provide important information about the athlete’s ability to harness “elastic energy” and not only muscular force.
There are many videos on YouTube showing the correct technique for the various jumps. Study them and have your players watch them so that they can master the mechanics of each test. Consistency is so important when collecting jump data. You want to standardize components of the test such as bench or box height in the drop jump, hands on hips to minimize or eliminate upper body contribution, and where possible, creating a specific joint angle or squat depth requirement in the NCM assessment. By doing so removes much of the “noise from the signal” and allows you to have more faith in the reliability and repeatability of your data from jump testing.
Jump testing also allows us to identify drop-offs in power from week to week. It builds a better picture of fatigue level. This only works if you can perform the tests consistently, and means the jump tests should be as simple as possible. You need to make the procedure so easy to understand that someone off the street can perform the test. As we already mentioned, deviation in jumping form is going to throw off any jump test and make the data less reliable. If you make any changes in a test, you’ll end up with corrupt data that isn’t going to have any relation to previous tests.
You also want to make it easy so that the athlete wants to jump. It should not take a lot of time, and the player needs to see that their performance in a jump test is as important as speed in a 40-yard dash or maximum weight lifted on the bench press. Conduct your tests so that they go smoothly and quickly for the players. Soon, you will have a wealth of data to look at over the course of a season. This is where weight room logistics and organization comes into play, and every coach has a different situation.
Also, most athletes not only want to see the data, but they want to know what it means and how it will affect what they’re doing. Nothing discourages an athlete more than forcing them to complete a bevy of tests and assessments, but not letting them see the results, or even worse, not doing anything practical with the information. This is their data, after all. In this all too familiar scenario, athlete motivation quickly dissipates, and data collection becomes drudgery.
You also need to keep your data collection and analysis simple. This is not just for the players; it’s for you too. Earlier we said you want to avoid “paralysis by analysis.” This point is true for all the training techniques we are talking about in this book including the jump tests. Before you go into any training protocol, know ahead of time what information you want to glean from the accumulated data. Doing so will help you focus on the segment of information you believe will best help the athlete perform better. There’s nothing wrong with starting with some basic information until you’re comfortable with it. From there, you can expand on how much you want to gather and interpret data from any training regime.
As we said earlier in the book, this is probably the best way to begin to develop a sports science program. It’s easy to get overwhelmed with information, even as a seasoned pro. Start with one or two data points, make sure they’re relevant, and build from there.
As for the data, you can accumulate helpful knowledge using research-grade force plates, but you can also get a lot of information using simpler methods like the contact mats. One football team learned a lot when they observed the absence of data. As the season wore on, players just couldn’t jump anymore due to the injuries from collisions and tackles. That’s a good example of how jump testing helps to reduce the chance of potential injuries with the concept that you can adjust training to help reduce the occurrence of bodily damage. By beginning to notice these trends, a good performance coach will be able to make adjustments to training to minimize injuries.
Not only will the jump testing data help determine how an athlete is progressing, it’s a great way to judge if the overall training for a team is on the right track. Whether your team sport has 12, 20, or 80 participants, you’re going to immediately see if the majority of the team is scoring higher on their jumps. If so, your power program is working. If not, obviously you want to make some changes, or find out if something else (like widespread under-recovery) is affecting the athletes’ performance. The data also reveals if the team results plateau at a certain level. If so, you might have to make adjustments to have your players do better on the jump tests again.
As an example, create a “jump profile” that identifies strengths and weaknesses in force application for each athlete. By putting each athlete into one of several “buckets,” you can easily individualize your jump and plyometric training within the team setting, and without having 30 athletes doing 30 different things. As any strength and conditioning coach knows, this is a recipe for utter chaos and lack of productivity. By putting athletes in the “needs concentric force” bucket, or the “needs elastic strength” bucket, you can have several athletes at a time working in their needed area, with only small changes in team workflow from performing different types of jumps.
Like almost every aspect of training, much of the success has to do with motivating your players. If they’re leaping up to catch a football or dunking a basketball, players don’t even think about it; they just soar. That is a lot different than putting your hands on your hips and jumping for training purposes. A coach once told the story about a volleyball player who seemed to have a vertical leap of three inches when doing a vertical jump test, but could make herself nine feet tall during a game.
The biggest issue with consistent jump tests is not the equipment you use or the time in practice when you conduct the tests, it’s the willingness of the athlete to learn how to do the test consistently and to put forth their best effort each time. Athletes are conditioned not to go all out if the reward is low. This is a constant coaching problem when running a practice. It is even a bigger problem in the day-to-day training of a player. It is up to coaches and performance coaches to make the jump tests an engaging experience for the players and one they want to do.
The nature of the tests also goes against a player’s natural inclination. Rarely does a player in any sport have to jump straight up in the air from a stationary position. Basketball and volleyball might be exceptions, but even in those sports, there is usually some forward movement leading to a jump. Use different vector jumps that make sense for your team. Sports that require horizontal force displacement may want to use a long jump. That is what we do in hockey. We just need to have a system for tracking and have a good protocol when conducting the tests. The single leg lateral jump is also a great measure for many sports and for identifying asymmetries.
Don’t be surprised if a player asks why they can’t do a running start before their jump. Explain that the jump tests are designed in such a way so that it is easy to repeat again and again. Taking a running approach would make the results inconclusive since it would be impossible to replicate the exact approach each and every time. An exception to this scenario might be tracking long-term development in basketball and volleyball, where approach jumps are part of the sport. However, these are probably not great tools to monitor fatigue and readiness due to the variability of the movements. Also explain to the player that by keeping the jumping technique simple, it’s easier to compare the athlete’s jumps with teammates.
A player will put more emphasis on anything that they can see as a direct connection to an improvement in their performance. While players realize lifting weights is a necessity, they’ll buy into doing squats a little more when they find their jump tests increasing because they understand that a higher vertical jump means a faster motor on the field. This is part of the process of the players understanding how and what the jump testing means in relation to their sport performance. Most training leads to gradual improvement, and this is one way an athlete will observe concrete results. Explaining the “whys” behind something like jump testing always beats out telling a player to “just do it.”
Figure out a good balance for your testing program. By that, we mean you have to judge how much testing works for you. Once a player buys into jump testing, their scores will improve over time the more they do it. However, there is a fine line between testing too much and the players losing interest or getting stagnant. You have to determine where that line is for motivation to stay high among the athletes.
It also doesn’t hurt to tap into the biggest motivation for athletes: competition. Players will give you their best jumps when they know this might be one of the judging criteria in deciding who plays and who sits. If you do not make the jump tests something that counts, athletes will lose interest. They simply get tired of it. Keep that in mind for almost any training element you run for your team. The player has to believe it is worthwhile to give their best effort.
As a performance coach, you need to be prepared for conducting your tests. Write down what you want to discover from the tests, how often you test, and how you will conduct them. Have a checklist ready to make sure you cover all the important points you need to talk to the athlete about related to the tests and to record your observations and data. When it comes to jumping tests, being thorough and disciplined about it prepares you for success. Your data will be consistent, the players will know what they’re doing, and you are in a better position to help the individual player and the team constantly improve.