Patrick W. Kennedy Jr., Somadeepti N. Chengalur and Barbara L. Hall
Patrick W. Kennedy Jr., David L. Wright and Gerald A. Smith
The precision of the kinematic values depends upon the methods of recording a subject’s motion. With the introduction of video recording techniques, questions have arisen concerning the accuracy of video compared with that of 16-mm film. Accordingly, the purpose of this study was to compare the accuracy of the two techniques for point reprediction using the Direct Linear Transformation method. Range poles, serving as boundaries of a cube with 20 known spatial coordinates, were filmed and videotaped. The 20 control points on the film and video recordings were digitized by three individuals. Nine sets of digitized points (three digitizers × three trials) for both film and video were compared with the actual three-dimensional coordinate values. Resultant mean errors were statistically significantly different (p<.05), 4.8 mm and 5.8 mm for film and video, respectively. However, from a practical standpoint the video error was only .29% of the calibrated field compared to .24% for film. Thus it is concluded that video techniques are comparable in accuracy to 16-mm filming methods.
Patrick Kennedy, Peter Brown, Somadeepti N. Chengalur and Richard C. Nelson
The performance of male and female swimmers (N = 397) competing in the preliminary heats of the four 100-meter swimming events during the Seoul Olympic Games was videotaped and later analyzed to determine stroke rate (SR) and stroke length (SL). These data were combined with age, height, and final time (FT) values for statistical analyses which included the relationships among these variables, comparison of male and female performance, and assessment of differences in the four events. The results revealed the following ranges of correlations between SR and SL (rs from −0.65 to −0.90), SL and FT (rs from −0.32 to −0.80), height and SL (0.19 to 0.58), and age and FT (-0.16 to −.051). The factor of SL was identified as the dominant feature of successful swimming performance. The men were older and taller, had longer stroke lengths and higher stroke rates (two of four events), and swam faster than the women. The differences in final times across the four events (freestyle fastest, breaststroke slowest) were due to specific combinations of SR and SL, with neither parameter being consistently dominant.