Biomechanics and Medicine in Swimming XI

conclusIon
The purpose of this study was to examine the effects of kinematic and
dynamic parameters on the crawl tumble turn performance. Results
showed that the time of maximum horizontal force is preponderant.
The glide phase is also critical. In the future, it would be interesting
to analyse the effects of more computed parameters, especially during
the contact phase (e.g. impulses and push-off angles) and to extend the
population (recreational female swimmers and elite male swimmers).
More subjects with the same protocol may help to provide a deeper
understanding of turning performance and develop a new hypothesis
about the swimming level (which could affect the ability) or the gender
(which could have an effect upon physical factors).
reFerences
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Blanksby B., Skender S., Elliott B., McElroy K., & Landers G. (2004).
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Chow J., Hay J., Wilson B., & Imel C. (1984). Turning techniques of
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plyometric training on the freestyle tumble turn. J Sci Med Sport, 2(2),
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Klauck J. (2005). Push-off forces vs. kinematics in swimming turns:
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Lyttle A. D., Blanksby B. A., Elliott B. C., & Lloyd D. G. (2000). Net
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Prins J. H., & Patz A. (2006). The influence of tuck index, depth of
foot-plant, and wall contact time on the velocity of push-off in the
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AcKnoWledGMents
The authors wish to thank Michel Knopp and Nicolas Houel from the
French Swimming Federation (F.F.N.) for their contribution during the
data acquisition process.
chaPter2.Biomechanics
Front Crawl and Backstroke Arm Coordination in
Swimmers with Down Syndrome
Querido, A. 1 , Marques-Aleixo, I. 1 , Figueiredo, P. 1 , seifert, l.
2 1 , chollet, d. 2, Vilas-Boas, J.P. 1, daly, d.J. 3, corredeira, r. ,
Fernandes, r.J. 1
1University of Porto, Faculty of Sport, Cifi2d, Portugal
2University of Rouen, Faculty of Sport Sciences, France
3Katholieke Universiteit Leuven, Faculty of Kinesiology and Rehabilitation
Sciences, Belgium
The aim of this study was to characterize the Index of Arm Coordination
(IdC) in swimmers with Down syndrome (DS). The IdC for the
front crawl (N=6) was -11.3% ± 5.2% and for the backstroke -13.5 ±
4.8%. This indicates that all swimmers demonstrated a catch-up mode
coordination in both strokes. Swimmers with DS did not adapt their
arm coordination as usually occurs in swimmers with higher level of
proficiency. In front crawl significant positive correlations were found
between IdC and the push phase as well as the propulsive phase. An
inverse correlation was found between IdC and the non-propulsive
phase. In backstroke, the catch-up coordination mode was used by all
swimmers. In this study hand lag time values far above those of elite
swimmers were observed. There was an inverse relationship between
IdC and velocity.
Key words: down syndrome, arm coordination, front crawl, backstroke
IntroductIon
Although cyclic activities, such as swimming, have traditionally been
assessed by velocity, stroke rate and stroke length, recent studies have
shown that the evaluation of arm coordination provides new information
to the classic analysis (Chollet et al., 2008). For assessing arm coordination,
Chollet et al. (2000) proposed the Index of Coordination
(IdC), which seems to give relevant information on a swimmer’s skill. In
the alternating strokes, i.e. front crawl and backstroke, arm coordination
is quantified as the time between propulsive phases of the right and left
arms, i.e., by the time lag between the propulsion moments of consecutive
strokes. According to Chollet et al. (2000), three possible modes of
coordination can be found: (i) catch-up, with significant discontinuity
between propulsion moments of both arms (IdC < 0%); (ii) opposition,
showing continuity between propulsive phases of both arms (IdC = 0%)
and (iii) superposition, in which overlapping of propulsive phases is seen
(IdC > 0%).
Studies focusing specifically on swimmers with Down syndrome
(DS) are very scarce. Since individuals with DS typically have a combination
of physical and cognitive limitations that significantly affect their
motor performance and contribute to a high variability of their motor
behavior (Epstein, 1989; Lahtinen, 2007), it is important to understand
if these typical characteristics, such as lower muscular strength, higher
percentage of body fat and anthropometric traits are reflected in their
inter arm coordination. The purpose of this study was therefore to characterize
the IdC in alternating strokes performed by swimmers with
DS, as well as to establish the relative duration of the propulsive and
non-propulsive phases.
Methods
Six international level swimmers with DS volunteered to participate in
this study (age: 20.2 ± 4.8 years, height: 154.3 ± 12.1 cm, weight: 58.4
± 14.1 kg and fat mass: 16.4 ± 11.6 %). The participant’s guardians provided
informed written consent to take part in the study, which was
approved by the local ethics committee.
All swimmers performed 2 x 20 m swims at maximal intensity, the
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