Concurrent criterion validity of a novel portable motion analysis system for assessing the landing error scoring system (LESS) test

The landing error scoring system (LESS) assesses the quality of a landing after a jump. The quality of the jump is usually evaluated using a three-dimensional (3-D) motion analysis system or a two-dimensional (2-D) video analysis visually rated by a clinician. However, both methods have disadvantages. The aim of this study was to examine the concurrent validity of a novel portable motion analysis system (PhysiMax System') in assessing the LESS score by comparing it to video analysis. The study population included 48 healthy participants (28.45 +/- 5.61years), each performing the LESS test while two video cameras and the PhysiMax' simultaneously recorded the jump. The Physimax' system automatically evaluated the LESS. Subsequently, the examiners scored the test by viewing the video recordings, blinded to the PhysiMax' results. The mean LESS score, using the video recordings and the PhysiMax' was 4.77 (+/- 2.29) and 5.15 (+/- 2.58), respectively, (ICC=0.80, 95% confidence intervals 0.65-0.87), mean absolute differences 1.13 (95% confidence intervals; 0.79-1.46). The results indicate a high consensus between the methods of measurement. The Physimax' system's main advantages are portability, objective evaluation and immediate availability of results. The system can be used by athletic trainers and physiotherapists in the clinic and in the field for jumping assessment.