A comparison of laser and video techniques for determining displacement and velocity during running

The reliability of a laser system was compared with the reliability of a video-based kinematic analysis in measuring displacement and velocity during running. Validity and reliability of the laser on static measures was also assessed at distances between 10 m and 70 m by evaluating the coefficient of variation and intraclass correlation co-efficient for each distance. Ten participants completed 3 running trials at self-determined fast, medium, and slow speeds. Running velocity was measured simultaneously by a laser and 2 video cameras (1 at 50 Hz, 1 at 100 Hz) within a 3-m measurement zone (V̄ _zone). The Root Mean Square errors for static distance measurement using the laser varied with distance, ranging from 4.5 mm at 10 m to 17.8 mm at 70 m. The test-retest reliability of running velocity measurements in the 3-m zone for the 50 Hz and 100 Hz cameras via intraclass correlation were estimated at .984 and .981, respectively. For the laser, test-retest reliability was estimated at ICC = .986. The results of this study indicated that the laser distance measurement device produced valid and reliable estimates of distance. When used within its limitations, the laser system will provide valid and reliable results, which can be made immediately available to the coach, performer, or user without the need to carry out time-consuming digitizing procedures.