Improving between-day kinematic reliability using a marker placement device.

3D motion analysis is commonly used to measure clinical outcomes, involving repeated measures over time. However, the day-to-day reliability of these measurements has been questioned and few attempts have been made to improve this reliability. Our purpose was to determine if a marker placement device (MPD) could improve day-to-day kinematic reliability as compared to manual marker placement. Ten healthy runners participated. Day-to-day comparisons of peak angles were made between manual marker placement and the use of an MPD. Reliability of each method was determined with intraclass correlation coefficients (ICC) and standard errors of measurement (SEM). The ICC and SEM values improved with the MPD. With the MPD, 7 out of 9 ICC values were >0.9 compared to only 3 when using manual marker placement. Additionally, the largest reduction in SEM values was in the transverse plane. Use of the MPD increases the power to detect smaller differences in studies of where gait is assessed over time.