Reproducibility and Repeatability of Intracyclic Velocity Variation in Front Crawl Swimming from Manual and Semi-Automatic Measurement

Purpose. Intracyclic velocity variation is an important kinematic parameter to evaluate swimming performance. It can be estimated by a fixed point at the swimmer’s hip. The aim of the study was to determine the reproducibility and repeatability of active light markers to measure intracyclic velocity variation in swimming. Methods. Reproducibility and repeatability were tested by image measurement, by five manual digitizing processes and five sessions of automatic tracking of a LED marker set in a swimmer’s hip. The procedures were evaluated by the intraclass correlation coefficient, and the agreement between the methods was evaluated with Bland-Altman plots. The reproducibility was excellent in both procedures. Results. The repeatability of manual digitalization ranged between satisfactory to excellent, while the repeatability of automatic tracking was excellent. In addition, the Bland-Altman plots displayed a good agreement between manual and automatic measurements. The automatic tracking was 27% faster than manual digitization. Conclusions. Active markers are promising to evaluate the intracyclic velocity variation of swimmers, with a faster response than the common manual processing