Biomechanics and Medicine in Swimming XI

BiomechanicsandmedicineinswimmingXi
Evaluation of Kinaesthetic Differentiation Abilities in
Male and Female Swimmers
Invernizzi, P.l., longo, s., scurati, r., Michielon, G.
Università degli Studi di Milano, Facoltà di Scienze Motorie, Milan, Italy
Events longer than 50 meters require some tactical skills in order to
manage the increase of fatigue, such as distributing the effort evenly
over the whole distance. Kinaesthetic differentiation skills are required
to achieve a very high precision of the movements. The repeatability of
two procedures, aimed to measure the kinaesthetic differentiation abilities
of swimmers was studied and the correlations between the actual
performances and the expected performances with respect to gender and
to the degree of change in velocity, were observed. Collecting the data
in a single day and during four days running resulted in reliable results.
Male swimmers seem to differentiate better than females and show a
generally higher coefficient of correlation between the actual and the
expected performance.
Key words: kinaesthetic differentiation, sensory perception, motor
control
IntroductIon
Physiological factors such as strength and power, and technique and
the ability to reduce drag, are the main factors determining swimming
performance.
Furthermore, any event longer than 50 meters requires that swimmers
employ some tactical skills, such as distributing effort evenly over
the whole distance, in order to manage increasing fatigue. Even highlevel
athletes tend to swim too fast the first part of the event compromising
the whole performance (Maglischo, 2003), especially during
short distance events.
The control of swimming pace largely depends on coordinative and
on sensory-perceptive abilities. The interaction between feedback and
sensory-perceptive information allows full control of the movement.
Furthermore, thanks to motor memory, the movement’s regulatory
system can precisely differentiate and manage the intensity of effort
(Bernstein, 1975). Kinaesthetic differentiation abilities seem to have a
progressive development with age, a plateau during puberty, an increase
from 16 years with a peak between 19 and 21 years, depending on gender
(Hirtz, 1988).
Kinaesthetic differentiation skills are thus important to perfect the
swim. Thanks to these abilities, swimmers can achieve a very high precision
of movement, having good control even when no visual feedback
is allowed, bringing the execution of the movement closer to the ideal
(Schicke, 1982), improving the “feeling of the water” and thus performing
better propulsive actions or better reducing drag forces (Colwin, 2002).
This study aimed to verify the repeatability of measuring and evaluating
the kinaesthetic differentiation abilities in good-level swimmers by
two different procedures based on simply swimming at different speeds.
The correlations between the actual performances and the expected performances
were also observed with respect to gender and to the degree
of change in speed.
Methods
Eighteen swimmers aged 13 to 19 years, of regional to national level,
participated in this study: 8 male swimmers (mean±SD, age 15.38±1.84
years, height 168.9±11.7 cm, weight 57.6±13.3 kg, BMI 20.0±2.4 kg·m -
2 ) and 10 female swimmers (mean±SD, age 15.75±1.39 years, height
167.8±6.0 cm, weight 57.9±8.8 kg, BMI 20.5±2.8 kg·m -2 ).
To measure their kinaesthetic differentiation ability, the subjects
performed a number of 25m front crawl trials at different paces corresponding
to 50% and 80% of the maximum speed.
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Each trial started without pushing-off the wall, the swimmer being
supported in a streamlined, prone position. First, the swimmers
performed a 25m front crawl trial at maximum speed (25m 100% ). The
speed corresponding to 50% and 80% of maximum was immediately
calculated by an MsExcel worksheet and communicated to the swimmer.
Afterwards they were asked to perform a total of eight 25m swims
as closely as possible to the requested speed (4 trials at 50% and 4 trials
at 80% respectively).
The time of each 25m performance and the time for the central 10
meters (from 7.5m to 17.5m) were recorded.
Feedback was given after each trial: the swimmers were advised of
their performance on a scale of 1 to 10, 10 corresponding to the 100%
(maximum), 8 for the 80% effort, and 5 for the 50% effort. This was done
in order to make the perception of speed easier for the younger swimmers.
Two different procedures were employed: i. Procedure 8/1, executing
the protocol in a single day; ii. Procedure 8/4, executing the protocol
over four days.
8/1: The swimmers performed 4 consecutive 25m front crawl trials
at 50% of the maximum followed by 4 consecutive 25m front crawl
trials at 80% of maximum on the same day. Full recovery was allowed
between trials and feedback from the previous performance was given,
as explained above.
8/4: The swimmers performed two trials per day, over four days.
Each day, a 25m front crawl trial at 50% of maximum and after full recovery
one at 80% of maximum, were performed. Feedback of the results
from the previous day was provided before starting.
Statistical analysis was carried out using SPSS 13.0 software. The
normal distribution of the data was verified by the Shapiro-Wilk test
and parametric statistics were applied. Test validity was analyzed by the
Intraclass Correlation Coefficient (ICC). Afterwards, by both gender
and procedure (8/1 and 8/4), the Pearson’s Correlation Coefficient between
the actual and the expected performance was calculated.
results
The validity and the repeatability of the procedures employed in this
study are shown in Table 1.
Table 1. Validity of the test (ICC)
Group 1
%
Changes in the mean 2.36
Typical error 5.92
Intraclass r (ICC) 0.77
The ability of the swimmers to perform 25m front crawl at a given speed
corresponding to 50% and 80% of their maximum is illustrated in Tables
2 and 3: correlations with the 25m 100% front crawl trials are shown. Both
procedures (all trials in a single day and two trials in four days running)
have been considered.
Table 2. Correlation (Pearrson’s) by gender in the 8/1 procedure between
the performance and the expected speed at 50%max and 80%max. Values
refer to the whole distance (25m) and to 7.5m to 17.5m (10m). * =
p