Biomechanics and Medicine in Swimming XI

BiomechanicsandmedicineinswimmingXi
Swimming in Eyesight Deprivation: Relationships
with Sensory-Perception, Coordination and laterality
Invernizzi, P.l., longo, s., tadini, F., scurati, r.
Università degli Studi di Milano, Facoltà di Scienze Motorie, Milan, Italy
Maintaining control of direction during displacement is important in
swimming, particularly for backstroke and open water events. Sensoryperception,
coordination and laterality can relate to the ability to swim
straight. This study aimed to analyze these relationships in front crawl,
backstroke and breaststroke swum in a condition of eyesight deprivation.
High correlation was found between the sensory-perception abilities
and the ability in blind straight swimming. A crossed dominance
right arm - left leg seems to be related to a better ability to manage the
swimming direction in breaststroke, but neither in front crawl nor in
backstroke.
Key words: sensory-perception, coordination, gliding
IntroductIon
Previous studies on technical and coordinative skills and on sensoryperception
abilities pointed out the importance of kinaesthetic differentiation
skills and of the ability to reduce the drag forces in swimming
performance.
We wondered about the role of kinaesthetic differentiation and coordination
in keeping control of the swim direction, managing straight
swimming. Usually athletes do not focus on it, thanks to the unconscious
collection of information through eyesight (e.g. the lane line, the
lane ropes, the walls). Swimmers should have good sensory-perception
and kinaesthetic differentiation skills because these abilities allow them
to perform the propulsive actions having good control even with no visual
feedback. Moreover they would be able to execute optimal swimming
close to a theoretical model (Schicke, 1982). This is important
in order to best manage the swimming direction, particularly in events
such as backstroke or open water.
The sensory-perception abilities are also essential to build “feeling
for the water” and they can be improved anytime by practice (Colwin,
2002). Furthermore they are closely related to coordination (Meinel et
al., 1984) and to balance, both during swimming and outside the water.
Visual feedback is closely related to balance, to sensory-perception improvement
and to the control of direction during displacement (Danion
et al., 2000). Relationships are also found between coordination and laterality
(hand dominance) (Oberbeck, 1989).
The evaluation of coordination can be accomplished through a test
based on the measurement of the maximal rotation on the longitudinal
axis the athlete performs (Starosta, 2004). The laterality of subjects
(hand dominance) could be calculated through the Hildreth index (Cilia
et al., 1996), from the frequency of the favourite side used while performing
a number of simple tasks.
The ability to reduce drag, connected to swimming specific sensoryperception
abilities, can be evaluated by a gliding or a dive and glide test
(Cazorla, 1993; Invernizzi et al., 2007).
The aim of this study was to analyze the relationships among sensory-perception
abilities, eyesight, coordination and laterality in maintaining
a straight swim during the front crawl, the backstroke and the
breaststroke, in young swimmers aged 8 to 14 years.
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Methods
Twenty-eight young swimmers participated in this study (mean±SD,
age 10.8±1.3 years, height 146.2±11.3 cm, weight 37.7±8.8 kg, BMI
16.9±2.2 kg·m -2 , arm span 148.7±13.5 cm).
To evaluate the trajectory of the swim without the support of visual
feedback, the swimmers were asked to swim wearing dark goggles
(Novàk, 1982). A total of 9 blind-trials were performed: strokes were repeated
three times in the sequence 25m front crawl, 25m backstroke and
25m breaststroke to avoid any conditioning effect due to the protocol.
Subjects swam in the middle of a double lane area, starting in a
prone or supine position, pushing off the wall with both legs. They were
asked to perform the swim as straight as possible, feeling the water displacement
only through kinaesthetic and vestibular sensory perception
feedback.
Scores (-5 to 5) were assigned depending on where the swimmers
touched the lane rope or the end wall (Figure 1). Assistants guaranteed
the safety of the subjects and the survey was supported by videorecording.
Positive scores indicated a deviation to the left whereas negative
scores indicated a deviation to the right. The scores have been inverted
for backstroke in order to have the same meaning of the direction of
deviation with respect to the swimmer’s body.
Swimmers performed the front crawl stroke breathing every three
armstrokes (alternating the side of breathing).
Figure 1. Experimental setting for the “blind swimming” evaluation.
The swimmers’ coordination was evaluated through a Coordination test
as suggested by Starosta (2004). Subjects had to jump on a 1 square
meter base (Figure 2), executing the maximal possible rotation on the
longitudinal axis during the flight. Athletes could make free use of upper
limbs. The degree of rotation was collected from the position of the feet
after landing. Two trials were performed for each direction of rotation.
The preferred direction to rotate was also detected from the results.