Comparison of Classical Kinematics, Entropy, and Fractal Properties As Measures of Complexity of the Motor System in Swimming.

The 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 (), approximate entropy () and the fractal dimension by Higuchi's method () were computed. Swimming data exhibited non-linear properties that were different among the four strokes (14.048 ≤ ≤ 39.722; 0.682 ≤ ≤ 1.025; 1.823 ≤ ≤ 1.919). The showed the lowest value for front-crawl, followed by breaststroke, butterfly, and backstroke ( < 0.001). Fractal dimension and had the lowest values for front-crawl and backstroke, followed by butterfly and breaststroke ( < 0.001). It can be concluded that swimming data exhibits non-linear properties, which are different among the four competitive swimming strokes.