Field-Based Evaluation of a Three-Camera Video-Based System for Three-Dimensional Kinematic Analysis of Powerlifting Movements
Keywords:
Powerlifting, Kinematics, Motion Analysis, Biomechanical Phenomena, Markerless Motion Capture, Resistance ExerciseAbstract
Objective: Three-dimensional (3D) kinematic assessment is important for quantifying movement mechanics during resistance exercise; however, laboratory-based motion-capture systems are often costly, technically demanding, and difficult to implement in field settings. Low-cost multi-camera video-based systems may offer a practical alternative, but their measurement agreement during complex multi-joint resistance exercises remains insufficiently established. This study aimed to evaluate the agreement between a three-camera video-based 3D kinematic analysis system and an expert manual video-digitization reference method during squat, bench press, and deadlift exercises performed under field-based conditions.
Methods: This cross-sectional agreement study included 42 male university powerlifters who performed competition-standard squat, bench press, and deadlift trials. Movements were recorded using three synchronized digital video cameras operating at 120 Hz and analyzed with Kinovea software. The proposed system was compared with an expert manual video-digitization reference method performed by blinded analysts. Selected joint angles and mean concentric barbell velocity were analyzed. Agreement between methods was assessed using Pearson correlation coefficients, intraclass correlation coefficients (ICC), root mean square error (RMSE), paired-samples t-tests, and Bland–Altman analysis.
Results: Strong correlations were observed across all measured variables (r = 0.946–0.982, p < 0.001), and agreement was excellent based on ICC values ranging from 0.944 to 0.981. RMSE values were low, ranging from 1.63° to 1.91° for joint-angle measures and from 0.015 to 0.016 m·s⁻¹ for barbell velocity. Paired-samples comparisons showed no statistically significant differences between the proposed system and the expert manual reference method for seven of the eight variables. Although the bench press elbow angle showed a statistically significant difference, the magnitude of this difference was less than 1° and was not considered practically meaningful. Bland–Altman analysis indicated minimal systematic bias and narrow limits of agreement across the measured variables.
Conclusion: The proposed three-camera video-based system demonstrated high agreement with an expert manual video-digitization reference method for selected 3D kinematic variables during squat, bench press, and deadlift exercises under standardized field-based conditions. Although these findings should not be interpreted as validation against laboratory-grade optical motion-capture systems, the system may provide a practical option for field-based biomechanical assessment when laboratory motion-capture facilities are unavailable.
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