Abstract
This article addresses how the Counter Movement Jump Test can reveal valuable insights into an athlete’s explosive strength skills.
Relevance for the Sport
The Counter Movement Jump (CMJ) is a simple, practical and well-established plyometric exercise and test used in strength and conditioning training to assess the explosive strength of an athlete’s lower body (1). Explosive strength is a critical component in many individual and team sports, such as athletics, soccer, volleyball, and basketball (2). Being able to jump higher or react faster than your opponent contributes to making a difference in competitive situations in these sports. For this reason, the CMJ is also used in recruiting and performance tracking of athletes. Additionally, the CMJ is applied by researchers to study biomechanics, muscle function, and performance.
The CMJ has been shown to be a valid and reliable measure of lower-body power (1). Additionally, performance in the CMJ correlates with relative strength during one-repetition maximum (1RM) back squats and power cleans (3), as well as sprint performance (4). This indicates that athletes who perform better in the CMJ, are also better at sprinting and maximal strength tests.
Last but not least, the CMJ is easy to perform and not fatiguing, unlike other jump tests such as the drop jump (5).
To perform a successful CMJ, an effective transfer of energy is fundamental. Therefore, stretch-shortening cycle (SSC) capabilities can also be evaluated with the CMJ (5). However, the CMJ uses a slow SSC (6). This means that the CMJ allows for a longer active state, giving the athlete more time. Athletes who have difficulties producing force rapidly probably perform better in the CMJ than in the squat jump (7).
Test Protocol
As shown in Fig-1, the CMJ is a double legged jump test characterized by a downward motion (= the countermovement) and a preceding maximal vertical jump. The athlete lowers down into a squatting position of self-selected depth by bending the hips and knees, followed by a rapid transition to jump upward as high as possible.
Hands should rest on the hip throughout the test for consistency with regards to intra-individual and inter-individual comparisons. Keeping hands on the hips will, however, reduce the ability to create energy as the arms cannot be used to create dynamic swing power. This is also why outcomes with and without arm swing cannot be compared against each other.
Follow the link for a more detailed test description of the ReGo Counter Movement Jump Test, including a step-by-step guide and an instruction video.
Outcome Parameters
The primary outcome metric of the ReGo Counter Movement Jump Test is Jump Height, represented by the change of the vertical position of the body between the instant of take-off and the peak positive vertical displacement. It is the most commonly measured parameter of the CMJ to provide insight into explosive lower-body strength.
A valuable analysis of the CMJ will look at metrics on all phases of the jump, however. For instance, it is not only interesting, how high an athlete is able to jump, but also how this jump height was achieved. In general, six key phases of the CMJ can be identified from force-time curves as depicted in Fig-2. In the following, the individual phases of the CMJ with the corresponding ReGo parameters are explained:
1. Weighing: In this phase the subject stands still and is weighed. This is important because the body weight is used to determine the onset of movement.
2. Unweighing: This phase marks the beginning of the countermovement, meaning the downward movement.
3. Braking: The subject reaches the bottom of the countermovement. At this point, the athlete has to apply force to stop the downward movement. The ReGo parameters Relative Peak Braking Force and Relative Net Braking Impulse relate to the maximum force and impulse that the athlete achieved during this phase. These parameters can be used to analyze the maximal eccentric strength capacities of an athlete.
4. Propulsion: In this phase, the athlete is moving upwards to push off the floor and propel up into the air as high as possible. This is considered a concentric action. The ReGo parameters Relative Peak Propulsive Force, Relative Net Propulsion Impulse and Time to Take-Off provide an indication of the athlete’s explosive strength and quickness (e. g., how fast he or she can get down into the squatting position and get back up again for the vertical jump). The ReGo parameter Takeoff Velocity relates to the maximal vertical velocity of the athlete’s center of mass (COM), which roughly occurs at the instant of take-off and is another metric to describe explosiveness.
5. Flight: This phase begins when the athlete takes off into the air. The corresponding ReGo parameter is the primary outcome of the CMJ, the Jump Height.
6. Landing: In this phase, the subject lands on the floor and sticks the landing.
Example
Let’s have a look at two examples: Vid-1 shows two athletes performing a CMJ with the ReGo system. Both are track and field athletes. Athlete A (left side) competes in throwing/jumping, and athlete B (right) side is a runner/sprinter. It is easily recognizable that athlete A displays a significantly greater jump height than athlete B: At 0,54 m he jumps twice as high as athlete B (0,27 m). How did athlete A achieve a so much greater jump height?
Both athletes take around the same time to lower into the squatting position, but athlete A is much faster in reversing this movement. This results in a shorter Time to Take-Off: Athlete A takes only 0,58 s from the initiation of the movement to the instant of take-off, but Athlete B needs 0,78 s. In the video, Athlete A is already high up in the air, while Athlete B is just about to leave the ground.
As a consequence, the relative peak braking force achieved by Athlete A is greater than of Athlete B (2,51 BW vs. 2,06 BW). The impulse required to stop the body mass from traveling downward at a certain velocity, is proportional to the impulse that was applied to reach this velocity. A given impulse can either be achieved by applying a great force over a short time or a small force over a long time (5). Therefore, Athlete A has to produce a greater braking force as this force is applied over a shorter time.
In summary, this indicates that Athletes A’s ability to rapidly produce force is greater than of Athlete B, which ultimately leads to a greater jump height.
Tips for Athletic Training
To generate explosive muscle power, athletes need to produce high levels of force and speed at the same time. Therefore, resistance training combined with plyometric training is a safe and effective way to increase speed-strength.
1. Resistance Training
An important factor is strength training. Maximum strength is related to power output and is arguably advantageous in many sports (9).
2. Plyometric Training
Plyometric training exercises contribute to train the explosive component and help improving jumping, sprinting, and agility performance (7).
Due to the force requirements of plyometric exercises, make sure the athlete has a general level of strength before starting plyometric training (7, 10). Plyometric training exercises should only be performed after an adequate warm-up and in a fully recovered state.
Level 1
The following exercise tips refer to plyometric training for enhancing explosive strength starting from a medium fitness level.
| Category | Name | Procedure |
|---|---|---|
| Exercise | Pogo Jump | o Start in an upright stance with slightly bent knees o Keeping the knees slightly bent and using only the lower legs, begin a vertical takeoff o Emphasize more flexion and extension in the ankle, than in the knee joint o After takeoff, keep the foot in a toes-up position |
| Volume | Recommendation | o 4 sets with 4-6 repetitions per session o Rest between repetitions: 5 – 30 seconds o Rest between sets: 30 – 90 seconds |
Level 2
The following exercise tips refer to plyometric training for enhancing explosive strength for advanced athletes.
| Category | Name | Procedure |
|---|---|---|
| Jumps | Squat Jump | o Begin in an upright position, feet shoulder-width apart o Interlace fingers and place palms at the back of the head o Bend the knees to get into a half-squat position o Immediately reverse the downward movement and jump up as high as possible o Extend the hips, knees, and ankles, land in the same position as takeoff o First, stick the landing, reset and start the next repetition o Progress to performing multiple repetitions without a break in between |
| Volume | Recommendation | o 4 sets with 4-6 repetitions per session o Rest between repetitions: 5 – 30 seconds o Rest between sets: 30 – 90 seconds |
Level 3
The following exercise tips refer to plyometric training for enhancing explosive strength for top level athletes.
| Category | Type | Procedure |
|---|---|---|
| Exercise | 5-5-5 Squat Jump | o Start with feet shoulder-width apart o One after another without breaks perform: 1. Five squats to a thigh parallel position 2. Quickly drop into a squat position five times 3. Quickly drop into a squat position and immediately explode vertically five times |
| Volume | Recommendation | o 5 x 6 repetitions per session o Rest between repetitions: none o Rest between sets: 30 seconds to several minutes |
All exercises adapted from: (9, 10)
Comments on Measurement Equipment
The measurement of the CMJ has historically relied on various methods such as force plates, contact mats, and video analysis.
In contrast to that, the introduction of the ReGo Sensor Insoles to jump testing as shown in this article presents a paradigm shift for coaches and trainers as they offer a cost-effective, valid, and reliable solution for CMJ assessments which is truly mobile and comes with fully automated data processing. Unlike traditional methods, ReGo provides the flexibility to conduct tests anywhere and anytime. Furthermore and in addition to the primary outcome Jump Height, ReGo offers functional information about the athlete such as center of pressure metrics during braking and propulsion phase and by specific timing information, along with the force and impulse metrics.
With regards to documentation and performance tracking, ReGo comes with labeling features and access to a reporting frontend which allows users to generate individual or team reports.
Individual reports are for one athlete and cover multiple tests such that intra-individual performance development over time can be evaluated. Team reports can be created for an infinite number of athletes and serve to compare inter-individual performance.
For both report types, exclusive reference data is available, covering numerous performance sports and age groups as well as female and male athletes. Reference data helps to classify the performance of your own athletes compared to average and best outcomes in the sport or age group, hence identifying strengths and weaknesses as a starting point for individualized training programs.
At large, the ReGo system helps trainers and coaches to enhance accessibility to jump testing such as the Counter Movement Jump, making it a valuable tool to objectivize performance evaluation protocols.
Literature
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