The aim was to examine the variation of linear and nonlinear proprieties of the behavior in participants with different levels of swimming expertise among the four swim strokes. Seventy-five swimmers were split into three groups (highly qualified experts, experts and nonexperts) and performed a maximal 25m trial for each of the four competitive swim strokes. A speed-meter cable was attached to the swimmer's hip to measure hip speed; from which speed fluctuation (dv), approximate entropy (ApEn) and fractal dimension (D) variables were derived. Although simple main effects of expertise and swim stroke were obtained for dv and D, no significant interaction of expertise and stroke were found except in ApEn. The ApEn and D were prone to decrease with increasing expertise. As a conclusion, swimming does exhibit nonlinear properties but its magnitude differs according to the swim stroke and level of expertise of the performer.

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 (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.

No abstract

No abstract

This study investigated the pre-movement and during-movement visual search behaviour (VSB) and quiet eye (QE) of 11 elite versus 10 sub-elite ten-pin bowlers, performing under high-anxiety and low-anxiety conditions. Pre-movement and independent of expertise, bowlers had more fixations and directed them to more locations when performing under high-anxiety compared with low-anxiety. Elite bowlers fixated at more locations closer to the pins in pre-movement than during-movement, with pre-movement QE occurring mostly at the breakpoint and middle arrows. During movement however, bowlers fixated closer to the foul-line at the middle and right dots and arrows, with during-movement-QE occurring at the middle dots and right arrows. Elite bowlers recorded longer QE durations during-movement rather than pre-movement, albeit a later onset during the longish five-step approach prior to ball release compared with sub-elite bowlers. Our results suggest that QE during-movement instead of pre-movement could be more pertinent in differentiating expertise during sporting tasks with a long movement phase and far-aiming target. The relevance of pre-movement or movement-QE in characterising expertise and performance could therefore be sport-dependent. This should be considered when investigating skilled action and developing training programs for skill acquisition.