Jumping towards field-based ground reaction force estimation and assessment with OpenCap.

Area of Science:

• Biomechanics
• Sports Science
• Motion Capture Technology

Background:

• Field-based biomechanical monitoring requires cost-effective methods for assessing kinetics and kinematics.
• Markerless motion capture offers potential for accessible biomechanical analysis.

Purpose of the Study:

• To evaluate the accuracy and usability of OpenCap for estimating ground reaction force (GRF) profiles during jumping.
• To validate estimated GRF variables against a gold-standard force platform.

Main Methods:

• Fifteen recreational athletes performed four jumping tasks (countermovement, squat, bilateral drop, unilateral drop).
• Full-body kinematics were captured using OpenCap (markerless motion capture).
• Vertical GRFs were estimated using a mechanics-based method and validated against force plate data.

Main Results:

• Six GRF variables showed bias or limits of agreement <5% across jumping movements.
• Seventeen and nineteen variables had bias and limits of agreement between 5-15%, respectively.
• Estimated forces with <15% bias adequately assessed within-athlete changes in GRF variables.

Conclusions:

• OpenCap demonstrates approaching acceptable accuracy for estimating GRF profiles in jumping movements.
• The method enables monitoring of force variables and segmental kinematics in field settings.
• This technology advances efficient, regular, and extensive biomechanical monitoring for researchers and practitioners.