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Ruud W. de Boer, Paul Schermerhorn, Jan Gademan, Gert de Groot and Gerrit Jan van Ingen Schenau

In speed skating, the amount of work per stroke is dependent on the component of the push-off force in the direction perpendicular to the gliding direction of the skate. One stroke consists of a gliding phase and a push-off phase in which the knee is explosively extended. Film and video analysis showed that the better skaters show a higher power production and no differences in stroke frequency. Differences in performance are related to differences in push-off mechanics. The faster skaters reach a higher angular velocity at the knee; the time during which the knee is extended is shorter. At the start of the push-off, the velocity of the body center of gravity in the horizontal direction is higher due to a passive falling movement in the frontal plane. It is concluded that the better skaters show a better timing that results in a more explosive and effective directed push-off.

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Tiago M. Barbosa, Kelly de Jesus, J. Arturo Abraldes, João Ribeiro, Pedro Figueiredo, João Paulo Vilas-Boas and Ricardo J. Fernandes

Background:

The assessment of energetic and mechanical parameters in swimming often requires the use of an intermittent incremental protocol, whose step lengths are corner stones for the efficiency of the evaluation procedures.

Purpose:

To analyze changes in swimming kinematics and interlimb coordination behavior in 3 variants, with different step lengths, of an intermittent incremental protocol.

Methods:

Twenty-two male swimmers performed n × d i variants of an intermittent and incremental protocol (n ≤ 7; d 1 = 200 m, d 2 = 300 m, and d 3 = 400 m). Swimmers were videotaped in the sagittal plane for 2-dimensional kinematical analysis using a dualmedia setup. Video images were digitized with a motion-capture system. Parameters that were assessed included the stroke kinematics, the segmental and anatomical landmark kinematics, and interlimb coordination. Movement efficiency was also estimated.

Results:

There were no significant variations in any of the selected variables according to the step lengths. A high to very high relationship was observed between step lengths. The bias was much reduced and the 95%CI fairly tight.

Conclusions:

Since there were no meaningful differences between the 3 protocol variants, the 1 with shortest step length (ie, 200 m) should be adopted for logistical reasons.

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Ruud W. de Boer, Gertjan J.C. Ettema, Hans van Gorkum, Gert de Groot and Gerrit Jan van Ingen Schenau

Characteristics of stroke mechanics of elite and trained speed skaters were measured during the skating of curves. Film and video analysis from the 5000-meter races at the Dutch National Championships yielded biomechanical variables that were correlated to performance. There are fundamental differences in push-off mechanics between skating the straight parts and skating the curves. The left stroke shows a more powerful push-off in the curve, caused by a greater push off angle compared to the right leg. The high speed and power output of the better skaters is a result of a high amount of work per stroke, caused by a short and effective directed push-off. These results strongly support the previous finding that skaters of different performance levels can be distinguished by differences in amount of work per stroke and not by differences in stroke frequency.

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M. M. Reid, Amity C. Campbell and B. C. Elliott

Tennis stroke mechanics have attracted considerable biomechanical analysis, yet current filtering practice may lead to erroneous reporting of data near the impact of racket and ball. This research had three aims: (1) to identify the best method of estimating the displacement and velocity of the racket at impact during the tennis serve, (2) to demonstrate the effect of different methods on upper limb kinematics and kinetics and (3) to report the effect of increased noise on the most appropriate treatment method. The tennis serves of one tennis player, fit with upper limb and racket retro-reflective markers, were captured with a Vicon motion analysis system recording at 500 Hz. The raw racket tip marker displacement and velocity were used as criterion data to compare three different endpoint treatments and two different filters. The 2nd-order polynomial proved to be the least erroneous extrapolation technique and the quintic spline filter was the most appropriate filter. The previously performed “smoothing through impact” method, using a quintic spline filter, underestimated the racket velocity (9.1%) at the time of impact. The polynomial extrapolation method remained effective when noise was added to the marker trajectories.

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Eva Piatrikova, Ana C. Sousa, Javier T. Gonzalez and Sean Williams

speed increases. 24 Considering the exponential relationship that exists between speed and energy expenditure in swimming due to the drag and changes in stroke mechanics swimmers encounter, 24 defining parameters of the CS concept using this method might be problematic in swimming. Indeed, Tsai and

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Roberto Baldassarre, Marco Bonifazi, Paola Zamparo and Maria Francesca Piacentini

stroke mechanics and energy cost of swimming. Pool swim test 27 Psychological aspects Baldassarre et al 36 5 W, 4 M 22.2 ± 5.6 Elite ANT, POMS, QU, RPE State anxiety does not seem to affect performance in elite open-water swimmers, despite the different level of athletes. 10 — De Ioannon et al 3 1 M 48

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Senda Sammoud, Alan Michael Nevill, Yassine Negra, Raja Bouguezzi, Helmi Chaabene and Younés Hachana

research may be summarized as follows: 1) variables related to functional fitness (eg, muscular strength or flexibility) that might influence stroke mechanics were not included in the model; 2) variables from other domains that may also play an important role in youth swimmers’ performance (eg, motor

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Frank Nugent, Thomas Comyns, Alan Nevill and Giles D. Warrington

that large amounts of practice, typically around 11 to 20 hours per week, are required to develop efficient stroke mechanics. 2 , 3 , 7 In recent years, a number of studies have investigated the effects of a low-volume, high-intensity training (HIT) program versus a low-intensity, high-volume training

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Pedro G. Morouço, Tiago M. Barbosa, Raul Arellano and João P. Vilas-Boas

Sports Sci . 2013 ; 31 ( 11 ): 1251 – 1260 . PubMed ID: 23560703 doi:10.1080/02640414.2013.778420 23560703 10.1080/02640414.2013.778420 32. Mason B , Formosa D , Toussaint HM . A method to estimate active drag over a range of swimming velocities which may be used to evaluate the stroke

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Kosuke Kojima, Christopher L. Brammer, Tyler D. Sossong, Takashi Abe and Joel M. Stager

practiced stroke mechanics for the remainder of the session. Swim Performance Tests Maximum average swim speed was assessed from the time required to swim from “flag-to-flag” (13.7 m, V max 13.7; eliminating the push off from the wall and the touch), measured during two 22.85-m freestyle sprints, with the