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Measurement errors when estimating the vertical jump height with flight time using photocell devices: the example of
A Attia1,2, W Dhahbi3,4, A Chaouachi3,5
1Higher Institute of Sports and Physical Education, Manouba University, Tunis, Tunisia.
Biology of Sport
|April 19, 2017
Summary
Estimating vertical jump height using flight time (FT) with photocell devices shows high correlation but significant systematic bias compared to force plates. While reliable, FT methods cannot replace force plate measurements for accurate vertical jump height assessment.
Area of Science:
- Biomechanics
- Sports Science
- Human Movement Analysis
Background:
- Vertical jump height (VJH) estimation commonly relies on flight time (FT) or vertical reaction force measurements.
- Photocell devices (e.g., Optojump) are frequently used for FT-based VJH estimation.
- Validating photocell-based VJH against a gold standard like force plates (FP) is crucial for accuracy.
Purpose of the Study:
- To assess measurement errors in VJH estimation using photocell-based FT compared to FP.
- To determine the intrinsic reliability of Optojump photoelectric cells for VJH estimation.
- To provide modality-specific equations for improved VJH estimation.
Main Methods:
- Twenty participants performed maximal squat jumps (SJ), counter-movement jumps (CMJ), and CMJ with arm swing (CMJarm).
- Simultaneous data acquisition using Optojump photoelectric cells and a force plate (FP).
- Analysis of validity (ICC, limits of agreement) and intra-session reliability (ICC, CV, SEM).
Main Results:
- High validity correlation (ICC: 0.98-0.99) and excellent intra-session reliability (ICC: 0.98-0.99) for Optojump.
- Significant systematic bias observed between FT and FP methods (-31% to -27%, p<0.001, large effect size).
- FT method underestimated VJH compared to the gold standard FP.
Conclusions:
- Optojump demonstrates high reliability and validity in estimating VJH, but exhibits systematic bias.
- The FT method, despite high correlation, cannot replace force plate measurements due to systematic differences.
- Modality-specific regression equations are proposed to enhance VJH estimation accuracy from FT data.
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