Quantifying Jump Height Using Markerless Motion Capture with a Single Smartphone

Area of Science:

• Biomechanics
• Sports Science
• Human Movement Analysis

Background:

• The countermovement jump (CMJ) is a standard test for evaluating lower-body explosive power.
• Accurate measurement of jump height is crucial for performance assessment and injury prevention.
• Traditional motion capture systems can be expensive and complex to set up.

Purpose of the Study:

• To assess the accuracy of markerless motion capture (MMC) using a single smartphone for measuring bilateral and unilateral CMJ jump height.
• To compare smartphone-based MMC jump height measurements against force plates and optical motion capture (OMC).

Main Methods:

• Sixteen healthy adults performed bilateral and unilateral CMJs, simultaneously recorded by force plates, OMC, and a single smartphone camera.
• Markerless motion capture (MMC) was applied to smartphone videos using OpenPose software.
• Jump height from MMC was validated against force plate and OMC data.

Main Results:

• Smartphone-based MMC demonstrated high reliability for quantifying CMJ jump height, with intraclass correlation coefficients (ICCs) ranging from 0.84 to 0.99.
• Accurate measurements were achieved without the need for manual video segmentation or camera calibration.
• The method proved effective for both bilateral and unilateral jump assessments.

Conclusions:

• Single smartphone-based markerless motion capture is a promising, accessible tool for measuring countermovement jump height.
• This approach offers a viable alternative to traditional, more complex motion capture systems for assessing lower-body explosive power.
• Further research can explore its application in diverse athletic and clinical settings.