Research Summary: ForceDecks Validity and Reliability

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Study Information

Collings, T. J., Lima, Y. L., Dutaillis, B., & Bourne, M. N. (2023). The validity and reliability of ForceDecks compared to laboratory force plates. Journal of Sports Science and Medicine, 1-15.  https://doi.org/10.1016/j.jsams.2024.04.014  

Link to the online report containing all test and metric results ‒ Reliability and Validity (tylercollings.github.io)

Purpose of the Study

This study aimed to evaluate the reliability and concurrent validity of VALD’s ForceDecks Dual Force Plate System against gold standard laboratory force plates across a range of common performance monitoring and rehabilitation-focused assessments.

Primary Objective: Quantify ForceDecks’ accuracy in measuring ground reaction forces (GRF) and center of pressure (COP) across a variety of:

  • Dynamic tests 
  • Isometric tests 
  • Balance tests 

Secondary Objective: Identify metrics with optimal and suboptimal validity and reliability, helping to educate users about which metrics are more and less reliable in practice.

Methods

Sixteen university students participated in the study ‒ ten males and six females, aged 18-40, all physically active and injury-free. Each participant underwent a series of tests to evaluate the concurrent validity of ForceDecks and AMTI force plates.

Two identical sessions were conducted one week apart to understand the test-retest reliability of both sets of force plates. These sessions incorporated twelve balance, dynamic and isometric tests using ForceDecks software, including:

  1. Quiet Stand
  2. Single Leg Range of Stability
  3. Squat Assessment
  4. Countermovement Jump (CMJ)
  5. Squat Jump (SJ)
  6. Drop Jump (DJ) 
  7. Hop Test
  8. Single Leg Hop Test
  9. Shoulder ISO-I
  10. Shoulder ISO-Y
  11. Shoulder ISO-T
  12. Isometric Mid-Thigh Pull (IMTP)
ForceDecks were placed atop AMTI plates so that data could be captured simultaneously.
ForceDecks were placed atop AMTI plates so that data could be captured simultaneously.

ForceDecks were placed atop the AMTI plates to enable concurrent recording from ForceDecks and AMTI plates at 1,000Hz. Force traces from both systems were analyzed directly in ForceDecks software, allowing a direct comparison of all ForceDecks metrics for validity testing. Capturing data at the same frequency from both systems enhanced the accuracy of the comparative analysis.

Reliability was quantified using intraclass coefficients (ICC) and validity was assessed through percentage differences, Bland-Altman analysis and Root Mean Square Error (RMSE).

Key Findings

ForceDecks and laboratory plates showed less than 1% difference in over 200 metrics [and] mean bias of under 2.5N (and 0.1mm for COP) across all analyzed tests.

Validity

ForceDecks vs. Laboratory Force Plates

Comparisons between ForceDecks and laboratory plates showed less than 1% difference in over 200 metrics across all tests.

Bland-Altman analysis also confirmed mean biases of under 2.5N (and 0.1mm for COP) across all analyzed tests, demonstrating ForceDecks' high measurement accuracy.

Example comparisons of vertical GRF time-series data between ForceDecks and laboratory force plates in CMJ (top) and Hop Test (bottom), showing near-perfect agreement between systems.
Example comparisons of vertical GRF time-series data between ForceDecks and laboratory force plates in CMJ (top) and Hop Test (bottom), showing near-perfect agreement between systems.
Example comparisons of vertical GRF time-series data between ForceDecks and laboratory force plates in CMJ (top) and Hop Test (bottom), showing near-perfect agreement between systems.
Example comparisons of vertical GRF time-series data between ForceDecks and laboratory force plates in CMJ (top) and Hop Test (bottom), showing near-perfect agreement between systems.

Reliability

ForceDecks and Laboratory Force Plates: Session 1 vs. Session 2

Metrics such as jump height, peak forces and power output consistently showed ICC values above 0.9, indicating excellent reliability across testing sessions.

Comparison of the test-retest reliability between ForceDecks and laboratory force plates using ICC. A: Distribution of ICC values for all metrics and tests for ForceDecks (top, orange) and laboratory force plates (bottom, navy). B: Mean ICC ± 1 standard deviation (SD) for all metrics of each test.
Comparison of the test-retest reliability between ForceDecks and laboratory force plates using ICC. A: Distribution of ICC values for all metrics and tests for ForceDecks (top, orange) and laboratory force plates (bottom, navy). B: Mean ICC ± 1 standard deviation (SD) for all metrics of each test.

When reviewing the distribution of ICC across metrics, it is obvious that some rate of force development (RFD) and time-based metrics were noticeably less reliable. However, these less reliable metrics were equally unreliable on both ForceDecks and laboratory force plates.

Therefore, it is reasonable to conclude that this is caused by natural inter-session variability in an individual’s performance of the same movement rather than any underlying inaccuracy of the force plates.

VALD’s Solution

The findings of Collings et al. highlight the suitability of ForceDecks for accurate and reliable assessment of GRF and COP. ForceDecks’ excellent concurrent validity and test-retest reliability suggest they are equally suitable as laboratory-grade force plates for performance monitoring, tracking rehabilitation progress and other common applications.

Read the full article or explore the full results.


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