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The Validation of a Portable Dual-Force Plate System for Assessing Countermovement Jump Performance

Authors:
Grace E Crowder
Grace E Crowder
Grace E Crowder
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Brett Pexa at High Point University
Brett Pexa
Kevin R Ford at High Point University
Kevin R Ford
Justin Phillip Waxman at SEA Limited
Justin Phillip Waxman
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The Validation of a Portable Dual-Force Plate System for Assessing Countermovement Jump Performance
Grace E. Crowder1*, Brett S. Pexa2, Kevin R. Ford3, and Justin P. Waxman1
1Department of Exercise Science, High Point University, High Point, NC
2Department of Athletic Training, High Point University, High Point, NC
3Department of Physical Therapy, High Point University, High Point, NC
Email: *gcrowder@highpoint.edu
Introduction
The analysis of kinetic data recorded via force platforms and
their associated software is becoming increasingly common in
the sport performance and injury literature, as portable systems
allow for greater opportunity to screen athletes on a massive
scale. However, understanding the validity of such systems is
necessary prior to their widespread use. Therefore, the purpose
of this study was to validate the use of a portable dual-force
platform against the current gold standard. We hypothesized
that the portable system would be a valid measurement tool.
Methods
As part of their pre-season screening, 69 NCAA Division-I
athletes (19.5 ± 1.3 yr, 1.8 ± 0.1 m, 79.0 ± 9.1 kg) performed
three maximal-effort countermovement jumps (CMJ) on two
separate force-plate systems. System #1 (Method A; gold
standard) consisted of two laboratory grade in-ground force
plates (AMTI, Watertown, MA) sampling at 1200 Hz, whereas
system #2 (Method B) consisted of a portable dual-force plate
system (Hawkin Dynamics, ME) sampling at 1000 Hz. Both
systems were integrated with their respective manufacturer-
provided software for data collection and reduction. Athletes
were allowed to swing their arms, and were instructed to jump
with maximal effort. Three-trial averages were calculated for
each athlete’s velocity at takeoff and vertical jump height.
Validity was assessed via Pearson’s correlation coefficients
between the two methods. Bland-Altman plots and 95% limits
of agreement (LOA) analysis were then used to assess absolute
measurement consistency between the two methods.1,2
Results and Discussion
Pearson’s correlation coefficients indicated strong positive
associations between methods for both take-off velocity (r =
0.862, r2 = 0.743; p < .001) and jump height (r = 0.863, r2 =
0.745; p < .001). Bland-Altman plots displaying the mean
difference between methods for take-off velocity and jump
height are shown in Figure 1A and 1B. LOA analyses (absolute
measurement error) revealed good agreement between methods
with mean differences (Method A – Method B) of 0.03 m/s
(95%LOA: 0.24, 0.30 m/s) and 0.26 cm (95%LOA: -7.10, 7.63
cm) for take-off velocity and jump height, respectively. In 95%
of the cases, jump height recorded using the portable system
(Method B) could be expected to range anywhere from 7.10 cm
lower to 7.63 cm higher than that measured by the gold standard
(Method A; Figure 1B). In support of our hypothesis, and in
agreement with prior work 3, these results indicate that the
portable dual-force plate system examined is a valid method for
evaluating CMJ performance. Figure 1A,B shows that mean
differences are reduced as take-off velocities and jump heights
increase, suggesting that the current findings may have been
influenced by within-subject factors such as individual effort or
level of experience. Allowing athletes to swing their arms
during CMJ trials may have also been a factor.
Figure 1. Bland-Altman plot displaying the mean difference
and 95% limits of agreement for vertical velocity at takeoff
[A] and maximal vertical jump height [B].
Significance
Portable force plates allow for more cost-effective options to
screen athletes outside of the laboratory. Although jump mats
and other inexpensive pieces of equipment can also be used to
assess vertical jump height, a portable dual-force system can
provide researchers and practitioners with force-derived
metrics in addition to information regarding asymmetrical
loading, countermovement depth, rate of force development,
etc.; and can thus serve a variety of applications. More on-site
athlete screenings may help improve performance techniques
and reduce injury risk.
References
1. Altman DG, Bland JK. Measurement in medicine: the
analysis of method comparison studies. Statistician
1983;32:307-17.
2. Bland JK, Altman DG. Measuring agreement in method
comparison studies. Stat Methods Med Res 1999;8:135-60.
3. Walsh MS, et al. The validation of a portable force plate for
measuring force-time data during jumping and landing
tasks. J. Strength Cond. Res. 2006,20(4):730-734.
A
B
... They can enhance the performance of individuals and make force measurements easier for researchers, coaches, and athletes to acquire. Past studies have been conducted to verify the in-ground and portable force plates in laboratories to prove the accuracy and reliability of the tested force plate [6][7][8][9]. ...
... In a previous study, three-trial averages were only calculated for each athlete's velocity at take-off and vertical jump height of the CMJ [9]. However, the jump height does not explain which method was used to calculate. ...
... A similar study used an experimental design without control of the arms. The author emphasized that allowing subjects to swing arms during CMJ trials may have been a negative factor for jump height [9]. Consequently, the jump strategy significantly impacted the mechanical characteristics, with deep jumps resulting in higher jump heights and concentric velocities than shallow jumps [35]. ...
The Validity of a Dual-Force Plate for Assessing Counter-Movement Jump Performance
Article
Full-text available
The objective of this study was to assess the concurrent validity of the Kunwei force plate system in relation to variables during a counter-movement jump (CMJ) task, in comparison to the Kistler in-ground force plate system, which is considered the “gold standard”. Methods: In a single testing session, the Kunwei force plates were placed directly on top of the in-ground Kistler force plate. This allowed for the simultaneous collection of vertical ground reaction forces from 30 participants (male, age = 22.8 ± 2.8 years, body mass = 74.3 ± 12.3 kg, height 178.2 ± 4.6 cm) during CMJ tests. The consistency between force plate systems was assessed using ordinary least products regression (OLPR) with bootstrapped 95% confidence intervals and the Interclass Correlation Coefficient (ICC). Results: There was no fixed or proportional bias in the CMJ variables measured between the force plate systems. The variables exhibited a strong correlation across the force plates during the CMJ task (ICC > 0.950, p < 0.01). Conclusion: The findings of this study indicate that there was no statistical difference between the Kunwei and Kistler force plate systems when evaluating common CMJ strategy and outcome variables, which are considered the gold standard. Hence, the Kunwei force plate can be regarded as a reliable substitute for the established industry benchmark in evaluating the force–time characteristics of the CMJ. Researchers, athletes, and coaches have the option to utilize this affordable and portable choice as a substitute for the more expensive laboratory-based force plate system. This alternative allows for the precise measurement of CMJ performance and force–time variables.
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... Portable force plates allow coaches to screen CMJ performance outside of the laboratory; thus, coaches are able to screen players more frequently and help improve performance techniques and reduce injury risk [22]. ...
... The countermovement jumps were performed on a portable force platform (Hawkin Dynamics), which has been shown to sample three dimensional components of ground reaction force at a frequency at 1000 Hz. The portable force plates used for this investigation have been found to be a valid method for evaluating CMJ performances [22]. ...
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... In addition, the bias observed in BW could be deemed as negligible due to no meaningful differences being observed in any outcome measures (i.e., JH), which are directly impacted by BW. Crowder et al. (7) also examined the validity of the HD force platform system against AMTI force platforms; however, their results should be interpreted with caution because it was unclear whether the HD force platforms were placed atop of the AMTI. In addition, they used inconsistent sampling rates (AMTI: 1,200 Hz and HD: 1,000 Hz) and also included arm swing during their vertical jump. ...
Validity of the Hawkin Dynamics Wireless Dual Force Platform System Against a Piezoelectric Laboratory Grade System for Vertical Countermovement Jump Variables
Article
  • May 2024
  • J STRENGTH COND RES
Dos'Santos, T, Evans, DT, and Read, DB. Validity of the Hawkin dynamics wireless dual force platform system against a piezoelectric laboratory grade system for vertical countermovement jump variables. J Strength Cond Res 38(6): 1144-1148, 2024-The aim of this study was to determine the criterion validity of the Hawkin Dynamics (HD) wireless dual force platform system for assessing vertical countermovement jump (CMJ) variables, compared with those derived from a Kistler piezoelectric laboratory grade force platform system. During a single testing session, HD force platforms were placed directly on top of 2 adjacent Kistler force platforms to simultaneously collect vertical ground reaction forces produced by 2 male recreational soccer players (age: 29.0 6 2.8 years, height: 1.79 6 0.01 m, mass: 85.6 6 4.7 kg) that performed 25 vertical CMJs each. Sixteen vertical CMJ variables pertaining to jump height (JH), flight time (FT), time-to-take off (TTT), countermovement depth, body weight (BW), propulsive and braking mean, and peak powers, forces, and impulses were compared between systems. Fixed bias was observed for 6 of 16 variables (peak and mean braking power, mean propulsion force, TTT, FT, and BW), while proportional bias was present for 10 of 16 variables (peak and mean propulsive and braking force, TTT, FT, peak and mean braking power, mean propulsive power, and BW). For all variables regardless of fixed or proportional bias, percentage differences were #3.4% between force platform systems, with near perfect to perfect correlations (r or r 5 0.977-1.000) observed for 15 of 16 variables. The HD dual wireless force platform system can be considered a valid alternative to a piezoelectric laboratory grade force platform system for the collection of vertical CMJ variables, particularly outcome (i.e., JH, reactive strength index modified) and strategy variables (countermovement depth).
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... Additionally, force-time data validity is often determined from direct comparisons to criterion force plates using stable known masses (i.e., 40 kg) (11). Others have compared countermovement jumps performed separately on 2 force plates (7), but assessing different force-time curves would not control for individual variation in jumping performances. However, comparing force-time software analyses of the same force-time curves is required to identify metrics that are in agreement across devices. ...
Analyzing Force-Time Curves: Agreement Among Commercially Available Automated Software and Custom MATLAB Analyses
Article
Full-text available
  • Feb 2022
  • J STRENGTH COND RES
With the growing prevalence of commercial force plate solutions providing automated force-time curve analysis, it is critical to understand the level of agreement across techniques. Thus, this study directly compared commercial and custom software analyses across force-time curves. Twenty-four males and females completed six trials of countermovement, squat, and drop jumps, and isometric mid-thigh pulls on the same force plate. Vertical ground reaction forces were analyzed by automated software from Vald Performance, Hawkin Dynamics, and custom MATLAB scripts. Trials were visually assessed to verify proper landmark identifications. Systematic and proportional bias among analyses were compared via least products regressions, Bland Altman plots, and percent error. Hawkin Dynamics had subtle differences in analysis procedures and demonstrated low percent errors across all tests (<3% error), despite demonstrating systematic and proportional bias for several metrics. ForceDecks demonstrated larger percent differences and greater biases for several metrics. These errors likely result from different identification of movement initiation, system weight, and integration techniques, which causes error to subsequent landmark identifications (e.g., braking / propulsive phases) and respective force-time metrics. Many metrics were in agreement between devices, such as isometric mid-thigh pull peak force consistently within 1 N across analyses, but some metrics are difficult and incomparable across software analyses (i.e., rate of force development). Overall, many metrics were in agreement across each commercial software and custom MATLAB analyses after visually confirming landmarks. However, due to inconsistencies, it is important to only compare metrics that are in agreement across software analyses when absolutely necessary.
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The Validity of Hawkin Dynamics Wireless Dual Force Plates for Measuring Countermovement Jump and Drop Jump Variables
Article
Full-text available
Force plate testing is becoming more commonplace in sport due to the advent of commercially available, portable, and affordable force plate systems (i.e., hardware and software). Following the validation of the Hawkin Dynamics Inc. (HD) proprietary software in recent literature, the aim of this study was to determine the concurrent validity of the HD wireless dual force plate hardware for assessing vertical jumps. During a single testing session, the HD force plates were placed directly atop two adjacent Advanced Mechanical Technology Inc. in-ground force plates (the “gold standard”) to simultaneously collect vertical ground reaction forces produced by 20 participants (27 ± 6 years, 85 ± 14 kg, 176.5 ± 9.23 cm) during the countermovement jump (CMJ) and drop jump (DJ) tests (1000 Hz). Agreement between force plate systems was determined via ordinary least products regression using bootstrapped 95% confidence intervals. No bias was present between the two force plate systems for any of the CMJ and DJ variables, except DJ peak braking force (proportional bias) and DJ peak braking power (fixed and proportional bias). The HD system may be considered a valid alternative to the industry gold standard for assessing vertical jumps because fixed or proportional bias was identified for none of the CMJ variables (n = 17) and only 2 out of 18 DJ variables.
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The Validation of a Portable Force Plate for Measuring Force-Time Data During Jumping and Landing Tasks
Article
  • Dec 2006
The purpose of this study was to determine the reliability and validity of a portable force plate when analyzing jumping and landing tasks. Subjects performed 3 drop vertical jumps and 3 drop landings on both a standard strain gauge laboratory force plate and a portable force plate. In contrast to typical laboratory installed force plates, the portable 6-component force plate can be easily transported and used onsite at various training or data collection sites and incorporates Hall effect technology. The measured parameters included maximum force and time to maximum force for initial stance of the both tests, maximum takeoff force, and time to maximum takeoff force for the drop vertical jump. The Pearson correlation coefficients for the drop landing and the drop vertical jump for maximum force (r = 0.942, r = 0.940), time to maximum force (r = 0.891, r = 0.920) and for drop jump maximum jumping force (r = 0.971), and time to maximum takeoff force (r = 0.917) were all high and indicate that the force data collected by a resistor-type portable force plate provide similar measures to a standard strain-gauge laboratory force plate. Additionally, the within session reliability of the drop landing and the drop vertical jump measured by the portable force plate showed high interclass correlation coefficients for examined variables of 0.979 and 9.67 for maximum landing force and 0.917 and 0.920 for time to maximum landing force, respectively. The interclass correlation coefficients for the maximum takeoff force and time to maximum takeoff force during the drop vertical jump were 0.991 and 0.86. The results indicate the force and timing measurements from the portable force plate were both valid and reliable. Use of the portable force plate may facilitate methods of force measurement that can be applied out into the field and therefore a valuable tool for on site landing and jump force measurements in a variety of settings for large numbers of subjects.
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Measuring agreement in method comparison studies
  • Jan 1999
  • STAT METHODS MED RES
  • 135-160
  • J K Bland
  • D G Altman
Bland JK, Altman DG. Measuring agreement in method comparison studies. Stat Methods Med Res 1999;8:135-60.