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Estimation of Vertical Ground Reaction Forces During Vertical Jumping in Children Using OpenCap.
Jiongyi You1, Zhicheng Lin1, Baifa Zhang1
1School of Sports, Southwest University, Chongqing 400715, China.
Sensors (Basel, Switzerland)
|June 12, 2026
Summary
The OpenCap system can estimate vertical ground reaction force (GRF) in young children
Area of Science:
- Biomechanics
- Pediatric Exercise Science
- Motion Capture Technology
Background:
- Vertical ground reaction force (GRF) is crucial for assessing young children's vertical jump development.
- Current methods for measuring vertical GRF are limited in large-scale physical fitness monitoring and educational settings.
- The efficacy of markerless motion capture systems like OpenCap for estimating pediatric vertical GRF requires further investigation.
Purpose of the Study:
- To evaluate the correlation and agreement between vertical GRF estimated by OpenCap and measured by a force platform in young children.
- To explore the specific characteristics of vertical GRF during young children's vertical jumps as estimated by OpenCap.
- To determine the potential of OpenCap for non-laboratory based assessment of pediatric vertical jump biomechanics.
Main Methods:
- Synchronous collection of kinematic (OpenCap) and kinetic (force platform) data during vertical jumps in 16 young children.
- Estimation of vertical GRF using OpenCap-derived whole-body center of mass vertical acceleration and Newton's second law.
- Statistical analysis using Pearson correlation and Bland-Altman methods to compare estimated and measured vertical GRF.
Main Results:
- OpenCap demonstrated moderate-to-high correlations for most vertical GRF characteristics, particularly time and impulse during push-off and flight phases (r > 0.85).
- Moderate-to-high correlations were also observed for peak and mean force during the push-off phase (r > 0.7).
- While time and impulse showed good agreement (bias < 15%), peak landing force exhibited weak agreement (bias > 40%).
Conclusions:
- The OpenCap markerless motion capture system shows potential for effectively estimating key vertical GRF characteristics in young children's vertical jumps.
- The push-off phase variables demonstrate the highest accuracy and agreement with force platform measurements.
- OpenCap offers a viable tool for field-based assessment of pediatric vertical jump performance, though rapid impact metrics require cautious interpretation.
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