Barbosa, Tiago M.Goh, Wan X.Morais, J.E.Costa, M.J.Pendergast, David2016-11-072016-11-072016Barbosa, Tiago M.; Goh, Wan X.; Morais, J.E.; Costa, M.J.; Pendergast, David (2016). Comparison of classical kinematics, entropy, and fractal properties as measures of complexity of the motor system in swimming. Frontiers in Psychology. ISSN 1664-1078. 71664-1078http://hdl.handle.net/10198/13440The aim of this study was to compare the non-linear properties of the four competitive swim strokes. Sixty-eight swimmers performed a set of maximal 4 × 25 m using the four competitive swim strokes. The hip's speed-data as a function of time was collected with a speedo-meter. The speed fluctuation (dv), approximate entropy (ApEn) and the fractal dimension by Higuchi's method (D) were computed. Swimming data exhibited non-linear properties that were different among the four strokes (14.048 ≤ dv ≤ 39.722; 0.682 ≤ ApEn ≤ 1.025; 1.823 ≤ D ≤ 1.919). The ApEn showed the lowest value for front-crawl, followed by breaststroke, butterfly, and backstroke (P < 0.001). Fractal dimension and dv had the lowest values for front-crawl and backstroke, followed by butterfly and breaststroke (P < 0.001). It can be concluded that swimming data exhibits non-linear properties, which are different among the four competitive swimming strokes.engSwimmingNon-linear parametersVariabilityPredictabilityComplexityHuman movementjournal article10.3389/fpsyg.2016.01566