ASSESSMENT OF ERROR LEVELS ACROSS THE DOMAIN OF A THREE DIMENSIONAL UNDERWATER MOTION CAPTURE METHODOLOGY

Assessing human movement underwater presents many challenges, and it is therefore important to understand error across the whole capture domain to ensure accuracy in resulting kinematics. This study assessed the accuracy across the capture domain of a submerged motion capture methodology. Six Qualisys cameras created an underwater capture volume of 8x2x2m. Average error levels across the domain were acceptable in two uncertainty trials (1.23mm ± 8.23mm and 1.34mm ± 9.65mm), but error increased at the ends and top of the domain. By selecting an area of interest for assessment that excluded areas with lower accuracy, error was reduced to 0.53mm (± 1.45mm). This study highlights the need to investigate error levels across a motion capture domain, particularly when this is a large volume, to ensure results obtained from investigations are reliable

TWO AND THREE-DIMENSIONAL ASSESSMENTS OF LOWER-LIMB KINEMATICS IN UNDERWATER FLY KICK

The purpose of this study was to compare sagittal plane lower limb kinematics of underwater fly kick measured using two and three-dimensional methods. Eight male participants (average FINA points score 801±138) completed underwater fly kick trials, recorded using a six camera Qualisys underwater system. Each trial was analysed using both two and three-dimensional methods. Lower-limb angles were significantly underestimated using two-dimensional methods, particularly at the hip where flexion and range of motion reduced by 13.73 degrees and 15.91 degrees respectively. The ankle and hip produce a large amount motion in the transverse and frontal planes. The results of two-dimensional analyses of underwater fly kick should be interpreted with caution due reductions in measured angles, and exclusion of out-of-plane kinematic information