Comparative analysis and validation of different measurement technologies for vertical jump performance

Abstract

Force plates (FP) are a primary tool used by the Malta Olympic Committee (MOC) in the Functional Diagnostic Lab (FDL) to assess vertical jump performance in athletes, particularly through the countermovement jump (CMJ) and the multi-rebound jump (MRJ) tests. The main aim of this dissertation is to develop a custom-built software to extract previously unattainable performance metrics from the MRJ test. The double integration method, using numerical trapezium integration, proved to be a viable approach to replicate CMJ performance metrics. However, this method is unsuitable for MRJ analysis due to integration drift, which introduced significant inaccuracies in deriving performance metrics. As a result, the flight time method was adopted as the preferred method for MRJs. The initial version of the software evaluated two force threshold methods to detect the take-off and landing instants. The first method employed a standard deviation method, while the second method applied a 10 N threshold on one leg. Both approaches replicated nearly all the metrics to within a 5% error. Following consultation with the FP manufacturer (Hawkin Dynamics) it was identified that their FP use a 25 N force threshold. Therefore, the final version of the software implemented this threshold which replicated the metrics to a near zero percent error when compared to the FP outputs. A secondary objective is to validate the use of FP using alternative technologies. Three motion capture methods were compared to assess discrepancies in different jump height definitions which resulted in discrepancies ranging from 4 cm up to 16.5 cm. These findings highlighted the importance of defining the jump height relative to the measurement technology used. When comparing the force threshold methods against motion capture technology, the standard deviation method proved most accurate, underestimating jump height by ~0.6 mm on average, and is best suited for symmetrical jumpers. Although the single leg 10 N threshold overestimated jump height by ~6.1 mm and the 25 N by ~4.2 mm, they aligned best with the FP software. All methods produced consistent results across 11 tests. Additionally, the smartphone accelerometer overestimated jump height by ~1 cm, showing improved accuracy over previous research, but was deemed unsuitable for FDL use due to limited reliability and automation. Therefore, the FP were still considered the gold standard for assessing vertical jump performance in the FDL at the MOC.