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Field-Based Concurrent Validity and Test-Retest Reliability of a Portable Force Platform During IMTP and
Uğur Fidan1, Mehmet Yıldız2, Zeki Akyıldız2
1Faculty of Engineering, Biomedical Engineering, Afyon Kocatepe University, 03200 Afyonkarahisar, Türkiye.
Bioengineering (Basel, Switzerland)
|June 26, 2026
Summary
The Fitforce portable force platform shows excellent reliability and validity for assessing isometric mid-thigh pull and countermovement jump propulsion. However, landing force measurements require cautious interpretation in stacked configurations.
Area of Science:
- Biomechanics and Sports Science
- Human Movement Analysis
- Performance Assessment Technologies
Background:
- Portable force platforms are vital for field-based neuromuscular performance assessment.
- Ensuring the validity and reliability of these portable systems is crucial for accurate data collection.
- Previous research indicates potential variability in portable force platform accuracy based on measurement variables and setup.
Purpose of the Study:
- To evaluate the concurrent validity of a novel portable force platform (Fitforce) against a laboratory-grade system.
- To assess the test-retest reliability of the Fitforce system under field conditions.
- To investigate the performance of the Fitforce during isometric mid-thigh pull (IMTP) and countermovement jump (CMJ) assessments.
Main Methods:
- Thirty male university students participated in the study.
- Participants performed IMTP and CMJ on a stacked configuration: Fitforce platform atop a reference laboratory-grade platform (ForceDecks).
- Concurrent validity was assessed using paired comparisons, ICC, R², and Bland-Altman analysis; reliability was tested across two sessions 24 hours apart.
Main Results:
- Very high agreement (ICC = 0.95-0.98) and excellent reliability (ICC > 0.96) were found for IMTP variables.
- High agreement (ICC = 0.92-0.96) and reliability (ICC > 0.97) were observed for CMJ propulsion variables (jump height, flight time, peak take-off force).
- Poor agreement (ICC = -0.88) and significant bias were noted for peak landing force, with moderate agreement for braking phase duration.
Conclusions:
- The Fitforce portable force platform demonstrates strong concurrent validity and excellent test-retest reliability for IMTP and CMJ propulsion metrics in field settings.
- Landing-related force measurements using the Fitforce in a stacked configuration should be interpreted with caution due to potential inaccuracies.
- The study highlights the suitability of the Fitforce for assessing propulsive movements but advises careful consideration for impact-related analyses.
