Mental representation of swimming strokes.
Ungerechts BE, Schack T
University of Bielefeld. Bielefeld, Germany.
Swimming strokes are mentally organised as motoric actions under the condition of (flow)
physics and limited energy reservoirs. Action representation is imagined to be organised
hierarchically in a tree-like structure as a network of so-called Basic Action Concepts (BACs) –
in long-term memory. BACs correspond to functional and biomechanical demands in concert
with the situational goals and constraints of motion. BAC’s are integrated mentally in a different
way per individual. The degree of integration of BACs is detected via Structural Dimensional
Analysis-Motoric (SDA-M). In this study SDA-M is applied to the underwater sequence of the
upper limbs of two butterfly swimmers. The purpose is to give inside how a) this method can be
applied in swimming, b) how the individual basis for action control in skilled voluntary motion
is detected by dendrograms and c) it can be used for better communication.
Keywords: cognition, anticipation, basic action concepts, swimming stroke analysis.
INTRODUCTION
Swimming strokes are mentally organised under the condition of (flow) physics and
limited energy reservoir. The mental organisation and neuronal control of any motion is
an issue of growing relevance, even from the biomechanical point of view, e.g. to ease
the communication between coaches and athletes (or other experts). Mental processes
can be subdivided into one emotional part and a cognitive one. Here, emphasis is placed
on the cognitive part, where the coding (planing, performing, storing) of motion takes
place as mental control in the long-term memory. Voluntary motions are considered to
be goal-directed acts which are organised and stored in a memory as based on
perspectives started by Bernstein (1). According to new research approaches by Schack
(2) perceptible events are representations of anticipated sensory effects following
perceptual-cognitive representations. The athlete is informed by sensory feedback
whether or not the motion was performed properly and effectively. In essence, an image
of the “reality” is stored as a cognitive unit on the basis of existing experience, and
voluntary actions are planned, executed, and stored in memory directly through
representation of their anticipated perceptual effects. This is different from a position of
motoric programs: supposedly nerves fires muscles individually but the numbers of
BMS06_MENTAL_REPRES_finaltouch.doc
1
fibres and the impulse patterns are different due to the goal of the motion (swimming
stroke, throwing action, etc). The feel for water is part of the mental control of a given
motion, which is based on anticipated perceptual effects, while permanent sensory
feedback is flexibly tuning the outcome. Tuning includs the task of regulation (or coordination) of motion eliminating excessive (odd) variables of motion in regard to the
purpose of the motion. According to present knowledge, completely different memories
are merging into a network. It is an accepted fact that never all details of a motion are
stored,; however, emphasis is placed on sensorial information. Consequently, motion
follows perceptual-cognitive representation and control, respectively. The steering of
motion(s) means perceptible events are linked to a functional performance.
As known, the spatio-temporal outcome can be determined biomechanically. The
question arise in which way functional or biomechanical demands of a motion is related
to perceptual-cognitive representation? According to Schack (2) so-called Basic-ActionConcepts (BACs) may serve as problem-solving-related features. First (in ontogenesis),
motoric and sensoric features are stored isolated which, by rehearsal, can later merge
into BACs, and motion is stored as a row of perceptual-cognitive effect representations.
BACs are tools for mastering the functional demands of motion as cognitive key-points
or to maximise the control of actions with lowest possible cognitive and energetic
effort. Functionally elementary actions, like arm stretching, sculling the hand or rotating
the trunk are mentally replaced by BAC’s. BAC’s are considered as mental counterparts
of functionally elementary components as well as transitional states of complex
movements (rotation, undulation, etc.), including spatio-temporal properties as well as
the afferent-perceptive-sensoric and efferent-motoric properties of motion, plus the
cognitive and emotional invariants of motion (per person).. In particular, BACs are
organised by hierarchical network(s) in long-term memory. BACs can be described
verbally as well as pictorially. This implies, that the mental representation of motion can
be studied by actions determined via Functional Motion Analysis (3). The replacement
is taking place without any special translation mechanism between perception,
representation and motion. The purpose of this paper is to demonstrate the relationship
between movement structures and representation structures, as well as the spatiotemporal structure of mental representation of butterfly arm-action.
BMS06_MENTAL_REPRES_finaltouch.doc
2
METHODS
The study is executed using PC-supported Structural Dimensional Analysis-Motoric
(SDA-M) introduced by Schack (2). This is a well-established procedure in the field of
cognitive psychology for ascertaining relational structures in a given set of concepts.
Hence the use of SDA-M will not detect the validity of biomechanical principles, it is
more a means to detect individual representation of motion. The SDA-M contains four
steps: (i) listing the BAC’s, or nodes, describing the motion in question by a special
split procedure (a multiple sorting task); (ii) a hierarchical cluster analysis is used to
transform the set of BACs into a hierarchical structure; (iii), a factor analysis reveals the
dimensions in this structured set of BACs, and (iv) the cluster solutions are tested for
invariance within and between the groups.
Besides the clustering SDA-M provides so-called dendrograms (tree-like diagram) in
which the distance between BACs is shown (measured in Euklidean units), as well as
the individual cognitive architecture of the motion (the BACs are expected to be listed
in a logic order). In order to get a workable set of BACs, which is presented in a splitprocedure, the butterfly arm motion below waterline was functionally analysed (Fig. 1).
Figure 1. Actions of a butterfly stroke from hand entry until its finish action.
The consideration of the hand motion in a fixed reference system remembers to the fact
that swimming stokes have, as purpose, to create momentum-induced propulsion based
on reactions of steady and unsteady flow. According to functional analysis conducted
by Ungerechts et al. (3), the path of the hand relative to water (fixed reference system)
is as follows, as used in teaching strokes (Fig. 2).
Some basics of the swimmer’s natural actions, like proper position of the hands or
elbow (upper arm in the beginning outward rotated), are not exclusively mentioned as
BACs because they are “inborn” while focus was placed on superfluous BACs like
“slicing hand(s)” means that the palms are facing thighs and little finger is leading (to
serve the unsteady flow effects and not to “minimise” resistance); quite often swimmers
BMS06_MENTAL_REPRES_finaltouch.doc
3
still follow the concept to “push backwards” with the palm oriented orthogonally to the
direction of motion.
Basic Action Concepts (BACs) of
underwater motion of arms/hands in
butterfly
1. forward trunk rotation
2. head enters water
3. fingers enter water
4. shrugging shoulders
5. hands out- and upwards
6. supination
7. backward trunk rotation
8. inward sculling of hands
9. pronation
10. elbow extension
11. hand slicing upwards
Figure 2. Side-view of the hand motion in butterfly stroke below water in a fixed reference
system, plus the BAC’s along the path (temporal aspects).
After familiarisation with the BAC’s (e.g. the meaning of each term) two swimmers are
asked via a multiple sorting task to judge the functional relation between BAC’s (which
BAC’s are direct neighbours or not) according to their best knowledge.
RESULTS
Results of this study are based on cluster analysis (Step II in SDA-M) and presented as
dendrograms for two swimmers. For interpretation the following aspects are relevant:
(i) the lower the value, the closer the BACs are located to each other in long-term
memory; (ii) the quality of order or grouping of the BACs (symbolised by numbers in
horizontal axis) reveals the understanding of the temporal aspects by the swimmer; (iii)
the clustering of the BACs symbolised by the horizontal bars indicate the quality of the
functional understanding of the swimmer. Inspection of the dendrogram (Fig. 3) reveals:
(i) the distance between most of the BACs (6 out of 9) is low, hence they are closely
related (the lower the value of a link between two items, the lower the distance between
the BACs in the long-term memory), (ii) the BACs are perfectly ordered per cluster, in
particular no BAC is singled out and (iii) the clusters demonstrate that the selected
classification of the representation structures match well with functional and
biomechanical demands of the task (for didactical purposes, in Fig. 3 the meaning of
clusters are introduced in words).
BMS06_MENTAL_REPRES_finaltouch.doc
4
Figure 3. The dendrogram of Swimmer A (calculated distances between BACs are
presented in Euclidean distances by right sided numbers; see text for further details).
The hierarchic cluster analysis for the mental representation structure of arm action in
butterfly reveals three clusters (representing functionally related solutions of the entire
task of motion) for Swimmer A: (i) forward rotation, head enters water and hands enter
water; (ii) hands outward-upward, supination of hands and backward rotation starts, and
(iii) extension of elbows, slicing hands before leaving water (the BAC “pronation” is
not significantly close enough). The BACs 1-4 serve the goal “fetch/catch of flow” and
sub-goals “entry of hands and body”. The BACs 5-8 serves the goal “momentuminduced propulsion (1. part)” while BAC “Supination” plays a centred role to induce
backward rotation of the trunk and create thrust. Finally, BACs 9–11 serve the goal
“Momentum-induced propulsion (2.Part)” starting with pronation including arm
extension and finished by slicing hands.
Figure 4. Original dendrogram of swimmer B (an international master swimmer).
The dendrogram obtained for the swimmer B (Fig 4) is different. Inspection reveals: (i)
the distance between most of the BACs (3 out of 9) is low, (ii) the grouping of BACs is
not perfectly ordered, two BACs are singled out, and (iii) the hierarchic cluster analysis
for the mental representation structure reveals three clusters: (i) fingers enter water,
BMS06_MENTAL_REPRES_finaltouch.doc
5
head enters water; (ii) shrugging shoulders, forward trunk rotation, and (iii) hands
out/upwards, backward trunk rotation. The mental representation of the arm action in
butterfly of swimmer B seems to be not “stable”. BACs like hands out/upwards and
backward trunk rotation are not attached fluently to the appropriate functional
neighbours, and shrugging shoulders is executed too early. It is likely that swimmer B
likes to fulfil all goals of stroking, however, needs some communication about the
functional attribution of the actions and the logic order.
DISCUSSION
Evidently the execution of swimming strokes are based on mental processes. Due to the
approach by Schack (2) that individual mental representation of actions in sports, like
swimming strokes, are connected to basic action concepts (BACs) which are structured
topologically not far from motion structure and includes biomechanical information.
Our knowledge about the mental representation is gradually improving as well as the
relation to biomechanical organisation. This will improve the specific communication
between coach and athlete about the detailed goals of swimming strokes beyond to
create flow, transfer momentum and raise efficiency. The participation in the sorting test
is a good means to increase individual mental efficiency and to decrease uncertainty
how to steer motion by overcoming superfluous degrees of freedom (a larger the
distance between BAC’s means more energy will be spend to make the motion
happening). Based on the dendrograms structural gaps or errors in the athlete’s mental
representation can be detected, e.g. when BAC occurs isolated from the others (not
linked to a neighbour) or the order of BAC’s is not appropriate to the functional relation
(central values of cluster analysis will serve interpretation). This study demonstrated
that the relation between mental and biomechanical structures can be detected
experimentally by uncovering the distances between selected basic action concepts
(BACs)which are closely related to functional actions.
REFERENCES
1. Bernstein, NA (1967). The co-ordination and regulation of movement. London:
Pergamon Press
2. Schack T (2004).The cognitive architecture of complex movement. Int. J. Sport
Exerc. Psychol. 2, 403–438.
3. Ungerechts, B, Volck G, Freitag W, (2002). Lehrplan Schwimmsport (Curriculum
Swim-Sport. Vol 1: Technique), Schorndorf/GER: Hofmann.
BMS06_MENTAL_REPRES_finaltouch.doc
6