Jurnal Of Swimming

©Journal of Sports Science and Medicine (2004) 3, 91-95
Research article
A KINEMATIC STUDY OF FINSWIMMING AT SURFACE
Jimmy Gautier 1􀀍, Laurent Baly 2, Pier-Giorgio Zanone 1 and Bruno Watier 1
1 Laboratoire Adaptation Perceptivo-Motrice et Apprentissage, Université Paul Sabatier, Toulouse, France.
2 Laboratoire d’Aérodynamique et de Biomécanique du Mouvement, Université de la Méditerranée,
Marseille, France
Received: 29 August 2003 / Accepted: 19 May 2004 / Published (online): 01 June 2004
ABSTRACT
Finswimming is a sport of speed practiced on the surface or underwater, in which performance is based
on whole-body oscillations. The present study investigated the undulatory motion performed by
finswimmers at the surface. This study aiming to analyze the influence of the interaction of gender,
practice level, and race distance on selected kinematic parameters. Six elite and six novices finswimmers
equipped with joints markers (wrist, elbow, shoulder, hip, knee, and ankle) were recorded in the sagittal
plane. The position of these anatomical marks was digitized at 50 Hz. An automated motion analysis
software yielded velocity, vertical amplitude, frequency, and angular position. Results showed that stroke
frequency decreased whereas the mean amplitude of all joints increased with increasing race distance (p
< 0.01). Mean joint amplitude for the upper limbs (wrist, elbow and shoulder) was smaller for experts
than for novices. Whereas that of the ankle was larger, so that the oscillation amplitude increased from
shoulder to ankle. Elite male finswimmers were pitching more acutely than female. Moreover, elite male
finswimmers showed a smaller knee bending than novices and than elite females (p < 0.01). This
indicated that elite male finswimmers attempt to reduce drag forces thanks to a weak knee bending and a
low upper limbs pitch. To sum up, gender, expertise, and race distance affect the performance and its
kinematics in terms frontal drag. Expertise in finswimming requires taking advantage of the mechanical
constraints pertaining to hydrodynamic constraints in order to optimize performance.
KEY WORDS: Swimming, undulations, technique, movement
INTRODUCTION
Finswimming is a speed competition sport practiced
at the surface or underwater with different monofins
of variable rigidity. Alike the motion of dolphins
(Videler, 1981), propulsion bears on the vertical
displacement of the whole body. The use of the
upper body is forbidden for propulsion purposes.
The vertical displacement of the body during the
stroke cycle has been described as wave-like
(Ungerechts, 1982). Since such motion could be
characterized by specific amplitudes of oscillations.
Such oscillations were also specified by a particular
frequency and phase relationship (Sanders et al.,
1995).
Our knowledge on finswimming bears mostly
on underwater finswimming. It was shown that the
wave-like motion traveled along the body in the
caudal direction and that finswimmers adapted their
undulations in frequency and amplitude, starting the
propulsive motion at the hip level (Baly et al., 2002).
Nevertheless, because of the air-water interface,
finswimmers’ motion is quite different in amplitude
and frequency at the surface than underwater.
Concerning finswimming at the surface,
Zamparo et al. (2002) performed a kinematic study
that quantified the efficiency of human swimming in
using fins. Another study revealed the effect of the
monofin shape on the propulsive forces by analyzing
the change in the swimmer’s velocity over one cycle
of the monofin’s motion (Tamura et al., 2002).
Finally, a finswimmer is at one and the same
time a propelling and a propelled body. Given the
speed reached (3.89 m·s-1), body pitch and knee
bending must be weak in order to limit the frontal
surface area, as defined by Vogel (1994), a main
factor of hydrodynamic resistance. The gliding and
the propulsion must be finely tuned in order to
Kinematics of finswimming
92
optimize performance. A previous study at the
surface showed that the race distance and practice
level increase the stroke frequency and the ankle
vertical amplitude (Gautier et al., 2004). However
the gender influence on kinematic parameters was
not taken into consideration.
In the present study, we hypothesized that the
gender affects finswimming performance in
association with the practice level and the race
distance. Thus, we aimed to quantify finswimming
at the surface in terms of kinematic parameters such
as the swimming speed, the movement excursion,
and the degree of knee bending according to gender,
race distance and practice level. Their analysis may
provide information useful to coaches and
technicians in order to reduce drag of the
finswimmer.
METHODS
The experiment was carried out in a 50 m pool. Six
elite finswimmers members of French National
Team (3 males, 3 females) and six novices (3 males,
3 females) who started competition six months ago
participated on a voluntary basis. For the elite group,
average age was 20 ± 4 years, body mass 69.1 ± 8.1
kg, and stature 1.74 ± 0.8 m. For the novices,
average age was 25 ± 3 years, body mass 64.6 ± 5.2
kg, and stature 1.69 ± 0.4 m. Finswimmers were
instructed to perform 3 random trials of 25 m per
race distance (100 m and 800 m). Using a snorkel,
finswimmers performed trials with their standard
monofins.
Passive disk markers were applied on selected
joints to facilitate their tracking and video analysis:
wrist, elbow, shoulder, hip, knee, and ankle were
visible to the camera throughout the stroke cycle.
Video images were collected from two digital
cameras (SONY VX-2000E, 50Hz). One digital
camera was immerged and securely fixed in a
watertight box at 0.15 m below the water surface
and recorded in sagittal plane. A calibration was
carried out separately for each trial, at the middle
tank and 5.34 m away from the camera. The width
of the optical field of view in the plane of motion
was 6 m. The other digital camera (SONY VX-
2000E, 50Hz) was placed in the axe of the first to
record motion above the water in order to control
whether the whole body was kept underwater,
except for the snorkel, vertex, and heel.
The markers were semi automatically tracked
(3D Vision, Kihopsys). The analysis period
comprised one complete stroke cycle starting from
the video frame corresponding to the first whole
body appearance. Body marks were seized to
determine a 5-segment human model: forearm, arm,
trunk, thighs, and shank. The knee bending angle
was determined using the relative angle between the
distal extension joint center of the thigh and the
shank. As for all biomechanical data, random error
from the digitizing process was reduced using a
recursive fourth-order Butterworth digital filter with
a frequency cut off at 4 Hz.
The analysis consisted of a repeated measures
ANOVA with gender (male vs. female) and
expertise level (novice vs. expert) as betweensubject
factors, and distance (100 m vs. 800 m) as
within-subject factor (N = 12). The dependant
variables were the velocity, the amplitude and the
frequency of oscillation, and the knee angle. All
effects were declared significant at a threshold of p <
0.05.
RESULTS
The average speed for 800 m was lower than for 100
m for the experts (2.09 m·s-1 ± 0.17 m·s-1 and 2.66
m·s-1 ± 0.26 m·s-1, respectively). Novices were
slower than experts (1.69 m·s-1 ± 0.11 m·s-1 and 2.07
m·s-1 ± 0.18 m·s-1 respectively). Irrespective of the
distance, males were faster than females (2.58 m·s-1
± 0.40 m·s-1 vs. 2.15 m·s-1 ± 0.31 m·s-1).
Table 1 shows that the average frequency of
stroke cycle decreased with increasing distance for
both experts and novices (p < 0.01). On 800 m,
novices were slower than elite finswimmers,
although their frequency was higher. Such frequency
was higher for males (1.61 Hz) than female (1.22
Hz) on 100 m as well as on 800 m males (0.81 Hz
vs. 0.61 Hz, respectively).
Figure 1 indicates that the amplitude of body
oscillation increased as a function of race distance (p
< 0.01) for all expertise levels. The upper limbs
amplitude of oscillation (i.e., wrist, elbow, and
shoulder) was smaller for experts than for novices.
Concerning the lower limbs (hip, knee, and ankle),
Table 1. Frequency (Hz) of stroke cycle of the most oscillant joints as a function of practice
level and race distance in elite (EXP) and novice (NOV) finswimmers. Data are means (±SD).
Frequency (Hz) EXP 100m NOV 100m EXP 800m NOV 800m
Hip 1.89 (.30) 1.54 (.26) 0.97 (.16) 1.01 (.16)
Knee 1.88 (.29) 1.53 (.28) 0.97 (.16) 0.98 (.17)
Ankle 1.88 (.29) 1.53 (.28) 0.96 (.16) 1.01 (.16)
Average 1.88 (.01) 1.54 (.01) ** 0.97 (.00) 1.00 (.02)
** significant difference (p < 0.01).
Gautier et al.
93
Figure 1. Range of vertical oscillation for elite (EXP) and novice (NOV) finswimmers in a 100 m and 800
m race. ** significant difference (p<0.05).
only the amplitude at the ankle level was larger for
experts than for novices. There was non difference
between male and female in vertical ankle amplitude
(0.56 m vs. 0.51 m, respectively). However, wrist
amplitude was significantly lower in female (0.22
m) than in male (0.26 m).
Knee bending was a factor of performance as
a function of the expertise (p < 0.01) associated with
the important vertical amplitude of the ankle.
Bending for experts was smaller than for novices
(119.25 ± 3.31 deg. and 104.60 ± 4.96 deg.
respectively on 100m). On the 800 m, novices’ knee
bending was higher than the elite’s one (94.85 ±
7.30 deg. vs. 108.87 ± 6.61 deg.). However, such
main effects on knee bending were comprised within
a 4-way gender x race distance x practice
interaction. This result will be discussed in the
following part.
DISCUSSION
The present study investigated the undulation
motion performed by finswimmers at the surface,
aiming to uncover the influence of gender, practice
level, and race distance on selected kinematic
parameters.
The undulation frequency and the swimming
speed decreased with the increasing race distance
from 100 m to 800 m for both expertise levels. This
suggests an adaptive decrement in the energy
expenditure for long races. Moreover, although
novices were slower than experts on 800 m, they
showed a higher frequency. Novices seem thus to
rush their action, privileging muscular strength and
quick motion in a attempt to swim faster. This point
to a lack of efficiency in the novices’ stroke
technique.
While stroke frequency decreased with
increasing race distance, mean joint amplitude
increased, irrespective of the expertise level. This
also suggests that both novices and experts can adapt
their energy output. Regarding motion amplitude,
the experts’ upper limbs appeared to act as a
stabilizing device. Expert finswimmers limit
potential energy due to upper limbs oscillation in
order to increase kinetic energy. In contrast, novices’
larger upper limbs amplitude and lower speed
indicate that potential energy is not transformed in to
kinetic energy as efficiently. Such an inefficacy is
reinforced by the fact that their shoulder operated as
a pivot point, so that the body behaved as a
pendulum rather than as an element along which a
wave was transmitted, and by the fact that their
frontal area was wider due to their larger upper
limbs amplitude. In addition, the novices’ shoulder
was nearer to the snorkel, as they were privileging
breathing and were not as used to submerge their
head as elite finswimmers. They did not take
advantage of buoyancy to balance their upper limbs.
Note that underwater, the undulatory motion starts
from the hip down to the ankle (Baly et al., 2002),
whereas at the surface this motion basically starts
from the shoulder for novices.
Regarding gender, females were slower than
males, and their stroke frequency was lower.
Females’ upper limbs oscillation was larger, while
that of the lower limbs was smaller. In spite of such
a large lower limbs oscillation and an important
knee bending, males were faster than females. They
appear to take most advantage of the maximal
acceleration generated at the moment of down-kick
than female (Tamura et al., 2002).
The experts’ vertical amplitude at the ankle
was larger than for novices irrespective of the
0,00
0,10
0,20
0,30
0,40
0,50
0,60
0,70
0,80
Wrist Elbow Shoulder Hip Knee Ankle
Oscillation vertical range (m)
EXP 100m
NOV 100m
EXP 800m
NOV 800m
** ** **
** **
**
Kinematics of finswimming
94
race distance. Likewise, thanks to the stabilizing role
of the upper limbs and the resulting streamlining, the
energy gained and stored was used to increase the
ankle vertical amplitude. Therefore the speed
reached by male finswimmers might be due to the
potential energy generated by the wrist amplitude,
which is transformed in kinetic energy and
transmitted caudally, in the line of the suggestion
made by Sanders et al. (1995). That amplitude
increased from hip to ankle in elite finswimmers,
particularly on 800 m, suggests a whip-like action
(Ungerechts, 1982). Both the reduction of frequency
and the rising of ankle amplitude induced a relief in
the foot pain resulting from the friction and the
rigidity of the monofin. Nevertheless, standard
monofin with specific length and rigidity allowed to
reach an amplitude and a frequency most adept to
the race. As suggested by Videler and Kamermans
(1985) for dolphins, elite finswimmers seem to
beneficiate from a large propellant area and to
accelerate during downstroke, which they optimized
by setting both a gliding and a propellant phase.
Interlimb dissociation allowed elite finswimmers to
reach and to preserve their high speed and to achieve
the best performance.
Expert male finswimmers exhibited a smaller
knee bending than females of the same expertise and
than male novices, inducing a limitation in frontal
drag. Indeed, at the surface, the body has better be
always profiled.
In comparison to underwater results reported
by Baly et al. (2002), the experts’ upper limbs were
used as a stabilizing device at the surface too. For
novices however, an efficient oscillation starts at the
shoulder level at the surface, whereas it starts at the
hip level underwater. Stroke frequency at surface is
higher than underwater for the same race distance,
whereas the ankle amplitude is bigger. For both
surface and underwater swimming, hip and knee
amplitude of oscillation is almost similar.
Interestingly, our out-water camera did not record
any marker. This suggests that even in surface
swimming, finswimmers tended to operate in a
quasi-underwater situation, probably because
underwater swimming is faster than doing so at the
surface. The ankle amplitude was larger underwater
than at the surface, despite the lower hip angular
excursion. Such results may be understood by the
larger mass of water efficiently used underwater.
CONCLUSIONS
Finswimmers cannot get away from body
streamlining in order to reach high level of
performance through the adaptation of stroke
frequency and motion amplitude to the constraints of
a race at the surface. Elite male finswimmers
achieve such a feat thanks to a weaker knee bending
and a low upper limbs pitching, reducing
concomitantly their frontal area and drag. Moreover,
they optimally transform potential energy into
kinetic energy during stroke cycles and transfer it
caudally, tantamount contributing to a propulsive
whip-like action. Expertise may be conceived as
taking advantage of the mechanical constraints
pertaining to hydrodynamics in order to optimize
performance. This empirical study represents a first
if incomplete step towards a more thorough
modeling of finswimming.
ACKNOWLEDGMENTS
We would like to thank Mr. Scribot at the CREPS in
Toulouse for his logistic support. We are also
grateful to the Extrem Vision Company for its
technical aid.
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Effect of practice level and race distance on
kinematics parameters in finswimming. Science &
Sports, In press.
Sanders, R. H., Cappaert, J. M. and Devlin, R. K. (1995)
Wave characteristics of butterfly swimming.
Journal of Biomechanics 28, 9-16
Tamura, H., Nakazawa, Y., Sugiyama, Y., Nomura, T.
and Torii, N. (2002) Motion analysis and shape
evaluation swimming monofin. In: The
Engineering of Sport. Eds: Ujihashi, S. and Haake,
S.J., Blackwell Science, Vol. 4, 716-724.
Ungerechts, B. E. (1982) A comparison of the movements
of the rear parts of dolphins and butterfly
swimmers. In: Biomechanics and Medicine in
Swimming. Ed: Hollander, A. P., Champaign,
Human Kinetics, 215-221.
Videler, J. (1981) Swimming movements, body structure
and propulsion. Cod Gadusmorhua, Symposia of
the Zoological Society of London 48, 1-27
Videler, J. and Kamermans, P. (1985) Differences
between upstroke and downstroke in swimming
dolphins. Journal of Experimental Biology 119,
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Vogel, S. (1994) Life in moving fluids. Second ed.
Princeton University press, Princeton. 467
Zamparo, P., Prendergast, D. R., Termin, B. and Minetti,
A. E. (2002) How fins affect the economy and
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Gautier et al.
95
AUTHORS BIOGRAPHY
Jimmy GAUTIER
Employment
Doctoral Student
Degree
MS in sports sciences
Research interests
Biomechanics of sports
gestures.
E-mail: jgautier@cict.fr
Laurent BALY
Employment
Project manager
Degree
PhD
Research interests
Biomechanics of sport
E-mail:
laurent.baly@decathlon.com
Pier-Giorgio ZANONE
Employment
Professor
Degree
PhD
Research interests
Dynamics of coordination and
learning
E-mail: zanone@cict.fr
Bruno WATIER
Employment
Assistant Professor
Degree
PhD
Research interests
Biomechanics
E-mail: watier@cict.fr
KEY POINTS
• Finswimmers are at one and the same time a
propelling and a propelled body. This study
investigates the undulatory motion performed
by finswimmers at the surface.
• Elite male finswimmers were pitching more
acutely than female swimmers and showed a
smaller knee bending than both novices and
elite female swimmers.
• Finswimmers tended to perform a dolphin-like
motion, which is used underwater situation
and optimizes hydrodynamics.
􀀍 Jimmy Gautier
Laboratoire Adaptation Perceptivo-Motrice et
Apprentissage, EA 3691, UFR STAPS, Université Paul
Sabatier, 118 route de Narbonne, 31 062 Toulouse cedex
04 – France.