Biomechanics and Medicine in Swimming XI

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chaPter2.Biomechanics
Different Frequential Acceleration Spectrums in
Front Crawl
Madera, J., González, l.M., García Massó, X., Benavent, J.,
colado, J.c., tella, V.
Universidad de Valencia, Valencia, España
This study analyzed the three different frequency spectrums of acceleration
that define the hip acceleration produced by front crawl swimmers
during a high-speed test. The swimmers (n=79) performed 25 meters
at maximum speed. The acceleration (m·s -2 ) was obtained by the derivative
analysis of the variation of the swimmer’s hip position
with time. The amplitude in the time domain was calculated with
the root mean square; while the peak power, the peak power frequency
and the spectrum area were calculated in the frequency
domain with Fourier analysis. Results showed that 27.85% of
the swimmers have a front crawl frequential spectrum of type 1,
30.38% of type 2 and 41.77% of type 3. Type 1 frequential spectrum
showed more concentration as opposed to producing accelerations
in front crawl and may be the cause of a better efficiency.
Key words: Front crawl swimming, acceleration, spectrum types.
IntroductIon
From the biomechanical point of view, swimming performance depends
on the mechanical interaction between water and the dynamical actions
of the swimmer’s body. From this interaction arises a force opposition
(i.e. propulsion vs drag) that is the source of the swimming velocity. All
this originates a succession of velocity fluctuations during every swimming
cycle (Miller, 1975). These intra-cycle velocity variations have been
studied to improve the swimming performance, considering spatialtemporal
parameters (Alves et al., 1994; Holmer, 1979; Miyashita, 1971;
Vilas-Boas, 1992 and 1996; Alberty et al., 2005; Tella et al. 2006).
Most of the available literature is mainly concentrated on velocity
analysis. However, the acceleration is the direct result of the force application
that is inferred in swimming. So, there will be major or minor
displacements of the swimmer depending on the forces magnitude
(Reiwald & Bixler, 2001), being the most effective the forces that produce
accelerations in the swimming direction (Bixler, 2005).
With the aim of characterizing the forces applied in the front crawl
stroke, Tella et al. (2008) analyzed the acceleration produced in the
swimming direction, focusing their analysis on both the time and frequency
domains (i.e., the power spectrum analysis) of the swimmers’ hip
acceleration. According to these results, the extent of the acceleration
generated at specific frequencies may directly influence swimming efficiency.
Also, this study presented three spectrum profiles in the frequeny
domain for front crawl swimming; one, two or more power peak (PP)
spectrums.
The main objective of this work was to identify the proportion of
the aforementioned type of spectrums in a larger number of front crawl
swimmers, and to analyze the differences of both temporal and frequency
parameters. As a secondary objective, we related these parameters
with performance.
Methods
After having signed an informed consent, all the procedures described
in this study fulfilled the requirements listed in the Helsinki Declaration
of 1975 and its later amendment in October 2000, seventy-nine
regional and national front crawl swimmers (mean ± standard error of
the mean (SEM) age 16.89±0.367 years; weight 63.172±1.3373; height
172.54±1.142 cm) took part in the experiments. The swimmers neither
suffered musculoskeletal pathologies nor restrictions, which may have
hindered their performance during events.
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