Biomechanics and Medicine in Swimming XI

BiomechanicsandmedicineinswimmingXi
Identifying Determinant Movement Sequences in
Monofin Swimming Technique
rejman, M. & staszkiewicz, A.
University School of Physical Education, Wroclaw, Poland
The aim of this study is to identify errors in leg and monofin movement
structure, which lower the effectiveness of swimming. The movement
cycles of six swimmers were filmed underwater in a progressive trial
(900 m at increasing speeds). Results due to kinematical analysis were
obtained as temporal data for: angle of foot bending in relation to the
shank, proximal end of the monofin in relation to the foot and for angle
of attack of the distal part and entire fin surface. The parameters were
selected according to an existing functional model of monofin swimming.
Hence, the identification of determinant movement sequences
and technical key elements in monofin swimming and their quantification,
make sense in order to anticipate and eliminate errors.
Key words: swimming, monofin, determinant movement sequence,
technique errors
IntroductIon
The surface area of a monofin is about 20 times larger than human feet,
and it is a more relevant source of propulsion. Monofin swimming for
learning, leisure or water rescue requires basic technical ability. At elite
sporting level, a perfect technique is required, as the monofin does not
“forgive errors”. An error may objectively be defined as a performance of
movement not in accordance with a given pattern. From motor point of
view, it may be a movement not in accordance with the original intention
(Brehmer and Sperle, 1984). A determinant movement sequence is
literally the general execution of movement activity which is determined
to be “correct” by objective parameters. The ability to verbally name a
movement precisely allows the combining of cognizant execution of action,
with the perception of what this action should be, supporting the
intellectual process of teaching and perfecting technique (Richard et al.,
2005).
Explicit conditions generating monofin propulsion form the basis of
several biomechanical analyses of technique, which develop a description
of the existing processes generating propulsion (e.g. Colman et al.,
(1999), formulate quality criteria for swimming technique (e.g. Shuping
et al., 2002; Rejman, 2006) and create a search through modeling
(e.g. Wu 1971). The remaining analysis is set aside for the aspects of
biomechanical application - useful in training procedures (e.g. Rejman
and Ochmann, 2009; Persyn and Colman, 1997). Therefore, the aim of
this study was to identify errors in leg and monofin movement structure,
which lower the effectiveness of swimming. The research assignments
formulated within the context of the use a monofin for maximum swimming
speed are: (1) the identification of errors in the leg and monofin
movement in order to describe their structure and scale; (2) the identification
of determinant movement sequences and key technical elements
of leg and monofin movement in terms of potential errors, with an aim
towards their anticipation and elimination; (3) the identification of the
relation between monofin swimming speed and the structure and scale
of errors, with an aim towards the isolation of determinant movement
sequences within the measure of quality of monofin swimming technique.
Methods
Six representatives of the Polish Monofin Swimming Team (homogenous
in terms of age, somatic parameters and championship level of
technique) took part in the research. They conducted a progressive test
(swimming 900 m at increasing speeds). To register parameters describing
the leg and fin movements, the swimmers were filmed underwater.
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Identification marks were place on the axes of the hip, knee and ankle
joints. The monofin was also marked (at the tail - where the plate is
joined to the feet, at the middle and at the edge of the fin). The marks
served to divided the fin into proximal (between tail and middle) and
distal (between middle and edge) parts, as well as to monitor the entire
surface of the fin. A random cycle (each 100m) from each swimmer
was chosen. SIMI System (SIMI Reality Motion Systems GmbH, Germany)
was used for kinematic analysis. The results were obtained in the
form of temporal data for the angles of bend at the foot in relation to
the shank (KAT), the proximal part in relation to the foot (ATM), the
angle of attack of the distal part (HME) and the entire surface of the
fin (HME). The existing model exactly these parameters were found to
create maximum swimming speed when they are optimized (Rejman
& Ochmann, 2009). Friedman’s test and Kendall’s coefficient, useful in
analysis of small groups were applied to confirm the existence of the
similarities in the data studied.
Figure 1. Example of quantification of errors registered in angular displacement
of the parameters studied
Within the range of illustrated errors made by swimmers in the time cycle
function (recorded during swimming of each 100m section of a trial)
a model analyzing the value of parameters was introduced. Information
was obtained on the scale and structure of error in relation to the model.
The range of errors were labeled and assigned to the relevant movement
sequence. The errors were quantified by calculating the size of the fields
estimated on the basis of the range of angles analyzed, which exceeded
(or did not attain) the boundary established by the model (Figure 1).
The values of fields estimated in a given cycle were summed for each of
the participants tested. In the next stage, the estimated ranges of errors
were illustrated by the movement sequence registered previously. Next,
these sequences were compared with sequences, which achieved the criteria
of the model, or demonstrated a slight comparable difference. The
juxtapositions supplemented information related to the range of errors
committed, forming the basis for the isolation of determinant movement
sequences. The identification of these sequences, along with the
results of analysis from the scale and structure of errors, allows the description
of key elements in the movement structure of legs and monofin,
in the occurrence of errors. The relation between errors committed
and swimming speed was also examined.
results
Based on information related to the scale and structure of errors committed
by swimmers (Figure 2, Table 1) the following generalizations
were formulated: (1) the fastest swimmer made fewer errors, in terms
of the parameters examined, than the slowest; (2) movement errors deduced
from the model were mainly related to angular displacement, with
the exception of the ankle joint angle during upbeat, performed by the
slowest swimmer; (3) based on the average values of sum of errors it