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

Abstract

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