Reliability of 3D measurement of pelvic and lower limb kinematics during two single leg landing tasks

Study aim: Three-dimensional (3D) motion analysis is one of the available methods used to evaluate body kinematics. The aim of this study was to assess the intrarater reliability of measurement of pelvic and lower limb kinematics during two single leg landing tasks using 3D motion analysis. Material and methods: 19 healthy volunteers (8 women, 11 men, age 23.1 +/- 2.8 years, weight 70.7 +/- 9.2 kg, height 174.8 +/- 6.7 cm) performed five repeated single leg hurdle hops (SLHH) (30 cm height) and five single leg drop landings (SLDL) from a box (40 cm height) in one measurement session with a 15-minute break and after marker replacement with 3D assessment. The intraclass correlation coefficient (ICC), standard error of measurement (SEM), and the smallest detectable differences (SDD) were used to examine the reliability of kinematic parameters during the landing phase. Results: The average intrarater ICC for SLHH was 0.92 (SEM = 1.69 degrees, SDD 4.68 degrees) and for SLDL was 0.96 (SEM = 0.81 degrees, SDD = 2.26 degrees). After marker replacement ICC decreased to an average value of 0.81 (SEM = 2.05 degrees, SDD 5.68 degrees) for SLHH and 0.82 (SEM = 2.36 degrees, SDD 6.53 degrees) for SLDL. Conclusions: Using the 3D method to evaluate pelvis and lower limb kinematics during single leg landing in one measurement session is a high reliability method for most parameters. Marker replacement is one of the factors that reduce the reliability of measures. When applying the SEM and SDD values, which the present paper contains, it is worth mentioning that the obtained results are caused by measurement error or they are due to individual issues.