Fig 1.
Device positions on the human body. VICON markers (green), GPS receiver between the scapulae (purple), LPS antennas on top of both shoulders (orange), center of mass COM (red).
Fig 2.
(Top) VICON test location on the pitch; (bottom right) scaled 3D model of the Rosenaustadion Augsburg. VICON area (blue), VID camera position (orange) at 21.6 m height and 82.0 m distance from the center spot. Pitch size: 105.0 x 67.0 m; (bottom left) additional camera platform.
Fig 3.
Sport-specific course (SSC) illustrated with exemplary VICON data.
Left: chronological sequence of movement patterns (1 = 15 m sprint into 5 m deceleration; 2 = 20 m sprint into 10 m backward running into 10 m forward running; 3 = 505 agility test; 4 = two rapid 90° turns; 5&6 = curved runs toward and away from the camera). Right: spatial representation of movement patterns. Starting position in the top-left corner.
Fig 4.
Left: Speed signal comparison of an accelerating-cruising-walking sequence before (blue) and after (red) 2 Hz low-pass filtering (criterion measure, gait-neutralized). Right: Spectral analysis of a center of mass (COM) speed signal recorded with VICON. Blue line: unfiltered speed signal; red line: 2 Hz low-pass filtered speed signal.
Fig 5.
Stance-neutralization with waypoint method.
The blue trajectory represents the actual horizontal movement of the center of mass (COM). In the example shown, the athlete moves from south to north and briefly stops in the center. Even if the athlete is standing still (both feet on the ground for a certain time), the COM trajectory would lead to artificial accumulating distances that are measured. The waypoint method (red trajectory) suppresses the micro movements that are not relevant for the gross motion.
Table 1.
Sample Size.
Table 2.
RMSE results.
Fig 6.
dRMSE (top), vRMSE (middle) and aRMSE (bottom). Box plots are used based on the five-number summary: minimum, first quartile, median, third quartile, and maximum. The central rectangle spans the first quartile to the third quartile. A red line inside the rectangle represents the median and the whiskers above and below the box show the locations of the maximum and minimum value. Red crosses indicate outliers. GPS = Global Positioning System; LPS = Local Positioning System, VID = video system; dRMSE = distance root mean square error; vRMSE = velocity root mean square error; aRMSE = acceleration root mean square error.
Table 3.
Results of the sport-specific course SSC.
Table 4.
Results of key performance indicators (KPI).