Altmann, S, Spielmann, M, Engel, FA, Neumann, R, Ringhof, S, Oriwol, D, and Haertel, S. Validity of single-beam timing lights at different heights. J Strength Cond Res 31(7): 1994-1999, 2017-The purpose of this study was to quantify the effect of different timing light heights on sprint time and the validity of measurement. Two single-beam timing gate systems were used to measure 30-m sprint time (splits at 5 and 10 m) in 15 healthy and physically active male subjects. System 1 was set up at a height of 0.64 m and system 2 at 0.25 m (initial timing light) and 1.00 m (each following timing light), respectively. Participants performed 3 valid trials. The recordings of a high-speed video camera were used as a reference. Sprint times of system 1 and system 2 differed significantly between each other and from the reference system at all distances (p < 0.001). Intraclass correlation coefficients and Pearson's r values between both timing light systems and the reference system were low to moderate at 5 and 10 m and moderate to high at 30 m. Bland and Altman analysis revealed that the agreement intervals were considerably higher for the comparison between system 1 and the reference system than for system 2 and the reference system. A valid measurement of splits at 5 and 10 m via the systems used in this study is questionable, whereas 30-m times have an acceptable validity, especially when using system 2. This study confirms the influence of methodological approaches on sprint times. Coaches and researchers should consider that results gained by single-beam timing lights at different heights are not comparable.
Background: The purpose of this study was to evaluate the accuracy of timing lights (TL) at different heights for measuring velocities during sprinting. Methods: Two sets of single beam TL were used to determine velocities reached in a flying 20-m sprint in 15 healthy and physically active male participants. In TL64, all TL were set up at a height of 64 cm, and in TL100, all TL were set up at 100 cm, respectively. Participants performed three valid trials. The recordings of high-speed video cameras were used as a reference. Results: ICC and Pearson's r values between both timing light heights and the reference system were almost perfect (0.969-0.991). Bland & Altman's LOA (95 %) indicated low systematic and unsystematic errors, with somewhat smaller LOA for TL100 (-0.013-0.121 m/s) than for TL64 (-0.060-0.120 m/s). Measures of betweentrial reliability of running velocities showed a high relative (ICC) and absolute (RMSE) reliability, with the reference system showing slightly better values in all reliability measures (ICC=0.935; RMSE<0.001 m/s) compared to TL64 and TL100 (ICC=0.894, 0.887; RMSE=0.107 m/s, 0.124 m/s, respectively). The usefulness, determined by comparing the typical error (TE) with the smallest worthwhile change (SWC), was considered as "OK" (TE ≈ SWC) for all three systems. Conclusions: Results suggest that TL at both heights (TL64 and TL100) can be considered as accurate, reliable, and useful in computing velocities during a flying 20-m sprint, and therefore can be recommended to both coaches and researchers.
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