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Article Title

COMPARISON OF GROUND REACTION FORCES DERIVED FROM FORCE PLATE AND MOTION CAPTURE SYSTEMS DURING VERTICAL JUMPS

Abstract

Eric M. Mosier1, Andrew C. Fry2, Justin X. Nicoll3, Dimitrije Cabarkapa2, Stephanie A. Sontag2, Rhonda Cross Beemer1 Northwest Missouri State University, Maryville, MO1; University of Kansas, Lawrence, KS2; California State University, Northridge, CA3.

PURPOSES: This investigation compared the ground reaction forces (GRFs) between a force plate and GRF derived from a markerless motion capture system (MCS) during a counter-movement vertical jump (CMVJ). METHODS: Healthy, recreationally active men (n=10; X±SD; age=22.5±2.1yrs, height=180.8±4.6cm, weight=80.8±7.5kg) and women (n=8; age=20.5±0.8yrs, height=171.7±5.7cm, weight=68.1±7.2kg) volunteered to preform 3CMVJsseparated by 30 seconds of rest. A 3-D markerless motion capture system (MCS; DARI Motion, Scientific Analytics, Lincoln, NE) was sampled at 50 Hz, while auni-axial force plate (Rice Lake Weighing Systems, Rice Lake, WI) and a data acquisition system (Biopac, Goleta, CA) sampling at 1000 Hz was used and resampled to 50 Hz for analysis. Participants begin the CMVJ standing on the force plate while in the MCS capture area. Ground reaction peak force (PF) was determined as the max force before takeoff, and ground reaction mean force (MF) was determined across the entire CMVJ from start of the motion to takeoff. Linear regressions were performed to compare MF and PF between the two devices (i.e. MCS vs. force plate) with the Pearson correlation (r), coefficient of determination (r2), and standard error of the measurement (SEM) calculated. Paired samples t-tests (MCS vs. force plate; p≤0.05) were performed on the MF and PF. RESULTS: Mean±SD and results are shown in table1. Paired samples t-tests indicated significant differences (<0.01) for MF and PF. Linear regression analysis indicated excellent agreement between MCS and force plate for MF (r=0.97, r2=0.93, SEM=13.99N) and PF (r=0.92. r2=0.84, SEM=35.72 N), respectively. CONCLUSION: Although significant differences were indicated, the linear regression analysis indicated that GRF can be accurately derived from a MCS without the use of a force plate. Furthermore, the intricate kinetic characteristics of human motion can be validly determined without being restricted to performing on a force plate.

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