Countermovement Jump Testing: reaching the data

When analysing the typical movements of a wide range of sports, jumping is clearly one of the predominantly performed actions by athletes. An increased jumping ability serves players in field sports competitions such as basketball or football, and of course various expressions of jumping are featured in track and field sports and a vast amount of Olympic events [1] .

Given its importance and prevalence, jumping ability has been thoroughly investigated in the last decades in both sport performance and laboratory settings alike, and jump testing has become a commonly used assessment tool in a variety of scenarios [2].

Of all the aspects of the jump motion, the analysis of the vertical component has been one of the more frequently adopted means of studying jumping performance, as it has proved a valuable, practical and time-efficient method of garnering useful and applicable data [3].

The first examples of vertical jump testing date back to 1921 with the Sargent’s Test, which was the first standardized protocol to assess the maximum standing vertical jumping ability, measured as the difference between standing reach and the top flight-phase reach.

A later iteration of the test was protocolled by Abalakov in 1938, and in this case vertical displacement was assessed with a measured-tape harnessed around the athlete’s waist.

One of the main contributors to the research of this field has also been Prof. Bosco, who during the 80s and 90s, authored a series of papers breaking down the different variables involved in vertical jump analysis and proposing a battery of tests to investigate said variables.

Today, vertical jump testing has been adopted as a multi-purpose tool. Some examples see this test as:

• A Performance Evaluation method: many professional sports clubs and leagues select their athletes based on their prowess during physical testing protocols such as the NFL Combine or NBA Combine;
• An Injury Risk Assessment: Impellizzeri et al have proposed how bilateral strength asymmetry during jumping constitutes a risk factor for musculoskeletal injury [4]. Moreover, Henderson et al have observed how athletes who generate the most power (those who jumped the highest in this case) are at greater risk of musculoskeletal injury [5].
• A Training Monitoring tool: repeated testing throughout a training cycle enables to monitor the effectiveness of a training program on vertical jump output;
• An Athlete Training Status Monitoring Tool: monitoring changes in performance on vertical jump tests during the training or competitive season, a practitioner can gain insight on the training status of the athletes. Taylor et al described how vertical jump testing is a wide-spread method for monitoring fatigue [6], while Halson suggested how such testing is important when detailing the correct external load imposed on an athlete in training [7].
• An Assessment Method during Rehab and Return-to-Activity Evaluation: having access to a comparison of pre-injury performance data is a precise system for assessing the recovery status during injury rehab protocols. Additionally, a precise assessment of landing and jumping mechanics will help establish the underlying re-injury potential, as Paterno et al [8], noticed through the analysis of asymmetries in this task for post-ACL reconstruction patients.

So what additional information, on top of vertical displacement, can be extracted from assessing an athlete’s ability to perform a vertical jump?

Let’s look at one of the most widely used tests, both in research published in scientific journals and in sport performance environments: the Countermovement Jump Test (or CMJ Test).

Markovic et al, defined the CMJ test as the most reliable and valid test for the estimation of explosive power of the lower limbs [9].

The CMJ test consists of a subject performing a vertical jump off two feet, from a standing position, with hands fixed on the hips (no arm-swing) and with a countermovement drop during the loading phase.

The simplicity of implementation of this test, with minimal instructions and learning needed for the subjects, plus its time-efficiency and repeatability, have made it a very valuable tool for practitioners.

Some of the variables that can be directly observed or indirectly estimated during the CMJ test are:

• Various expressions of Force and its application or dissipation over Time: this is the main analysis of the athlete’s capability of producing force and interacting with the ground and gravity.
• Acceleration: this is an important assessment of how the athlete can accelerate body segment in an efficient, sequential and synchronized manner.
• Flight Time: this is the resulting outcome of the force application by the subject and the main performance goal.
• Range of Motion: this can help in the understanding of the individual best-possible jumping biomechanics as related to his/her body’s architecture.
• Symmetry: this can highlight potential performance leaks and inherent injury risks.
• Neuromuscular Control: this can aid in the definition of the athlete’s overall neuromuscular profile.
• Postural Control: this can prompt a further investigation into structural deficiencies or detrimental postural tendencies.

The amount of data that can be extracted from this test is however directly related to the available technology used to perform the assessment.

The main options available to the Biomechanist, Sport Scientist or Strength and Conditioning Coach are:

• Video Analysis: Using a 2D slow-motion video recording of a subject performing a CMJ Test, it is possible to quantify, through the use of a biomechanical analysis software, the flight time and/or the vertical displacement of the subject during the execution of this test. One positive aspect of this type of analysis is that it can be performed in virtually any location and the costs involved are quite limited. However, the quality of the video analysis is strictly correlated to the quality of the apparatus (camera resolution, frame rate, software capabilities) and the setup (camera angles, proper triangulation), and will therefore provide very rough data.

More elaborate structures, such as 3D Motion Analysis systems, are available on the market and are able to provide results that are much more precise due to the integration of specialized cameras, physical markers and advanced software for data integration and analysis. Systems like these tend to be a very expensive option, and additionally require a permanent installation, making them a prerogative of higher-budget lab settings.

• Accelerometers: Highly portable in nature and easy to implement, these systems are a versatile and cost-effective option for measuring both acceleration and displacement during the CMJ test. The Gyko system is equipped with the latest generation components: it is able to supply acceleration measurements of up to 16g and angular velocities of up to 2000°/s with an acquisition frequency of 1000 Hz. The Bluetooth data transmission provides real-time measurements directly to the PC via the Microgate software that, with its scientifically validated algorithms, offers simplified data processing and interpretation. Thanks to its special accessories (i.e. pelvic belt, vest, belts for the upper and lower limbs and a magnetic support for weights and barbell) Gyko never influences the motion of the subject and it can be use outdoors on any kind of surfaces. In the context of jump testing, Gyko placed near the centre of mass thanks to the appropriate belt enables enriching the temporal data with a variety of information regarding the dynamics of the jump. The system allows indeed to analyse the movement of the trunk during the flight and contact phase thus providing, among other things, the following additional parameters:
  • Eccentric and concentric work and duration;
  • Force, Velocity and Maximum Power;
  • Rate of Force Development and Landing Rate.

Finally, Gyko can be synchronized and used together with OptoJump.

• Force Plates: Force plates have been used for several decades to assess the subject’s interaction with the ground during vertical jump testing. This type of instrument will provide accurate readings of the forces involved in the medio-lateral, antero-posterior and vertical directions during the performance of a countermovement jump. Additionally, by analysing how the force is applied over time, it is possible to assess the subject’s impulse and rate of force development during the motion.

The practical problem with force plates is that in most cases they can effectively be used only in a laboratory setting equipped with specialized platforms that allow the force plate to be slotted into the ground (therefore avoiding subjects “stepping up” on the platform). Moreover, the systems tend to be very expensive and their use, depending on the software, potentially quite intricate.

• OptoJump: jump analysis is one of the strengths of the OptoJump system. Thanks to the optical detection technology, it allows the measurement of flight and contact times with an accuracy of 1/1000 of a second. In addition to these two fundamental parameters, the algorithms implemented in the software provide all the main values used in the performance analysis: jump height, power (in repeated jumps), rhythm, etc. Furthermore, the use of high frequency cameras that can be positioned in the space as desired, allows recording the images of the tests performed, synchronizing them perfectly with the detected events. It is thus possible to evaluate the "jump quality" by enjoying the in-depth video analysis, while also taking advantage of the possibilities offered by the dedicated utility. The standard OptoJump protocols allow the execution of all the classic jumps (i.e. squat jump, countermovement jump, drop jump and plyometric jumps), but the software flexibility also permits the definition of new types of tests which is increasingly becoming of interest in the field of monitoring and rehabilitation.

BIBLIOGRAPHY

[1] Payton C., Bartlett R. “Biomechanical Evaluation of Movement in Sport and Exercise” Routledge, New York NY, 2008.

[2] Roger M. Enoka, Neuromechanics of Human Movement, 5th edition. Human Kinetics, 2015.

[3] Hamill J., Knutzen K., Derrick T., “Biomechanical basis of human movement",4^th Edition. Wolters Kluwer. Philadelphia, PA.

[4] F. M. Impellizzeri, E. Rampinini, N. Maffiuletti, and S. M. Marcora, “A vertical jump force test for assessing bilateral strength asymmetry in athletes,” Med. Sci. Sports Exerc., vol. 39, no. 11, pp. 2044–2050, Nov. 2007, doi: 10.1249/mss.0b013e31814fb55c.

[5] G. Henderson, C. A. Barnes, and M. D. Portas, “Factors associated with increased propensity for hamstring injury in English Premier League soccer players,” J. Sci. Med. Sport, vol. 13, no. 4, pp. 397–402, Jul. 2010, doi: 10.1016/j.jsams.2009.08.003.

[6] K.-L. Taylor, D. W. Chapman, J. B. Cronin, M. J. Newton, and N. Gill, “Fatigue monitoring in high performance sport: a survey of current trends,” vol. 20, no. 1, p. 12, 2012.

[7] Halson S, “Monitoring Training Load to Understand Fatigue in Athletes,” Sports Medicine, vol. 44, no. Suppl. 2, pp. 139–147.

[8] M. V. Paterno, K. R. Ford, G. D. Myer, R. Heyl, and T. E. Hewett, “Limb asymmetries in landing and jumping 2 years following anterior cruciate ligament reconstruction,” Clin. J. Sport Med. Off. J. Can. Acad. Sport Med., vol. 17, no. 4, pp. 258–262, Jul. 2007, doi: 10.1097/JSM.0b013e31804c77ea.

[9] G. Markovic, D. Dizdar, I. Jukic, and M. Cardinale, “Reliability and factorial validity of squat and countermovement jump tests,” J. Strength Cond. Res., vol. 18, no. 3, pp. 551–555, Aug. 2004, doi: 10.1519/1533-4287(2004)18<551:RAFVOS>2.0.CO;2