Luc Collard

Why have swimmers neglected the “fish kick” technique?

Given that horizontal-plane undulation (“fish kicking”) just under the water surface is more effective (from a hydrodynamic point of view) than vertical-plane undulation (“dolphin kicking”) (Lighthill, 1975), why then do expert swimmers experts not use this technique after the turn and before resuming their arm stroking action? Fourteen national-level swimmers (6 males and 8 females) were timed over 15m and 25m trials while dolphin kicking and then fish kicking. A comparative analysis revealed the strong potential of fish kicking (which equates to dolphin kicking on the side). Over 25m, the fish kicking times were only slightly slower than the dolphin kicking times, and this was in the absence of prior training. Over 15m and at no more than 1 metre below the surface, the swimmers went significantly faster in the side position (p<0.05). A multifactorial analysis (MFA) revealed that the determinants of high performance while kicking underwater are relatively independent of the swimmer’s absolute speed (e.g. personal best for 50m front crawl), gender, age and weight. In contrast, in the population of swimmers studied here, being a backstroke or butterfly specialist and being short were factors that appeared to favour speed in the undulation trials.

Do dangerous sports specialists play more dangerously? An experimental study on sample selection.

Dangerous/extreme sports specialists are often accused of reckless behaviour. The present research study sought to test that assumption. Sixty-six sportspeople (mean ± SD age: 20.3 ± 1.2) of both genders (including nine extreme sports specialists) took part in a sports game (‘chickie run’) which obliged them to choose between cautious and risky behaviours. The participants played each other in pairs, i.e. 65 matches per player. In ‘chickie run’, the two players start 20 m apart and run straight towards each other. If the players collide at the meeting point, they each lose 2 points. If both players ‘chicken out’ by deviating from their line, each scores 2 points. If one chickens out and the other does not, the defecting player scores 0 and the non-defector gains 4 points. In theory, players should defect every other time in the iterated ‘chickie run’ game (as long as one does not take account of the opponent’s reputation). Out of the 2145 recorded matches, the sportspeople generally tended to play according to this symmetric risk (expected Nash equilibrium: 1 point per match). Only extreme sports specialists tended to maximize their score (1.34 points per match) by playing significantly more cautiously (they deviated 3 times out of 4, with a Maximin profile, p < 0.01).

Comparison of performance levels over 25 m by 11 expert swimmers using anguilliform-like and carangiform-like techniques; eel-like swimming versus carangiform-like swimming

Performance levels over 25 m for two underwater swimming techniques (carangiform- and anguilliform-like swimming) were compared in 11 national-level, competitive swimmers. Several indicators of propulsive efficiency were recorded: leg oscillation frequency and amplitude, head oscillation amplitude and the Strouhal number (St). Video analysis suggested that head movement amplitude correlates with performance levels in anguilliform-like swimming (dolphin kicking with the arms alongside the trunk). However, analysis of St did not lead to the expected results in our evaluation of carangiform-like swimming (i.e. conventional dolphin kicking, with the arms stretched out in front). Although the anguilliform-like technique is not used in competitive swimming, it turned out to be as effective in our swimmers (despite the lack of prior practice) as the carangiform-like technique. This paper discusses the relevance of two techniques inspired by the animal kingdom and which are vying to become the “fifth stroke”.

Average swimming speeds for 6 sections of the 50-meter backstroke race: Comparison of performance in zones swum underwater or at the surface in 12 international short course events

We measured the speed of 12 international-level swimmers (6♀ and 6♀) for 6 sections of the 50m backstroke race in a short course (25m) pool (0-5m; 5-15m; 15-25m; 25-30m; 30-40m; 40-50m) by breaking down the races using video analysis. Our assessment revealed that swimmers went faster when underwater (independently of the benefit obtained by pushing off the pool wall in the 0-5m and 25-30m zones) than when they swam at the surface. These results were supported by the per-zone speed ranking established by the vast majority of 151 sports students acting as observers. The latter viewed each race 3 times, in order to divide up the race into the 6 zones using frame-by-frame images (with an index of agreement of more than 76%, according to Pareto’s criterion). Only the per-zone speed rankings for the 3 slowest female swimmers deviated from the majority ranking (using Kendall’s L statistic), as the result of a shorter underwater segment during the 2nd length. Despite being considered (by the sport’s rules and in scientific terms) as a subsidiary and disruptive element of propulsion, underwater dolphin kicks are responsible for the highest speeds in this type of event.

Impact of Self-Fulfilling Prophecies on Progress and Motivation in Fosbury-Flop

In high jump, the determination of a student’s theoretical best performance helps the elaboration of the PE teacher’s early expectations. By affecting the student’s motivation profile, knowledge of these expectations will have an impact on his progress. The study focuses on two ninth grade classes, where both are presented with a contest, a test and a questionnaire at the beginning and at the end of the cycle. We determine their actual and theoretical performances as well as their initial and final levels of self-determination. Only one class has been given knowledge of their theoretical performance. Then, two variables are analyzed: the “learning” variable linked to the duration of the cycle, and the “pedagogic modality” variable, whether the student is aware of his theoretical performance or not. The ANOVA (analysis of variance) tests performed have showed no significant impact of these variables on the performance, but their interaction is an important factor over the perceived progress. This significance is also observable on our subjects self-determination levels, intrinsic motivation and their overall skills. By fostering the teacher’s perception, knowledge of the theoretical performance does not affect directly the student’s performance but heightens his intrinsic motivation and favors the progress in his skills.

Chapitre 10. Proposition d’une méthodologie par grille d’observation pour décrypter les capacités : illustration dans un pôle d’Activités et de Soins Adaptés

L’approche par les capacites (Sen, 2000) semble etre un hebergement theorique pertinent afin d’interroger les conditions de vie des personnes en situation de handicap et/ou de perte d’autonomie. Neanmoins, cette prometteuse approche des problematiques sociales reste ombragee par des ecueils d’ordre methodologique. Ainsi, bien que son fondateur insiste sur la necessite de comprendre la signification que les acteurs donnent a leur vie et a leurs choix dans l’environnement qui est le leur, il reste clairement ancre dans une demarche positiviste, objectiviste, quantitative. Cet article se donne pour objectif de presenter une methodologie par grille d’observation permettant de depasser cet ecueil. Son deploiement permet d’apprehender le rapport de la personne a autrui, l’espace, le temps et les objets dans une situation sociale donnee. A titre d’illustration, nous construisons une telle grille pour une situation de repas dans un Pole d’Activites et de Soins Adaptes (PASA) accueillant des personnes presentant une maladie d’Alzheimer ou une maladie apparentee.