Biomechanics and Medicine in Swimming XI

BiomechanicsandmedicineinswimmingXi
other players. This position increases the resistance, which in water has a
very significant impact due to the density of the medium. Furthermore,
starting statically, the water polo player cannot push from the edge of
the pool and thus uses the technical act of “trudgeon”. The acceleration
phase requires additional energy expenditure, as it is overloaded by the
higher drag due to the additional water mass in front of the swimmer.
These considerations lead to revise the power values that are required
in water polo players to move to a given swimming speed. Rodriguez
(1994) found higher energy expenditure in tests performed by water
polo compared to swimmers. Performing on a reference athlete a series
of towing tests, we compared the values of drag, defining the power
required to move, comparing the technique of water polo with normal
freestyle. Estimating these values at different speeds during a model
game, we suggest that the mechanical power required to the water polo
players could be more than three-fold higher than that required for freestyle
swimming at the same velocities.
This study highlights the importance of developing specific training
programs for water polo, addressing the higher requirements of
mechanical power, taking into account the specific movement techniques
and comparing the distances travelled using different swimming
techniques. However, further acquisitions will be performed with more
athletes and matches, with the aim of identifying the specific differences
between the models.
reFerences
Bonifazi, M., Adami, A., Veronesi, A., Castioni, M. & Cevese, A.,
(2005). Comparison between passive drag and drag during leg kicking
of the crawl stroke in top level swimmers. Medicina dello Sport,
58, 81-87.
Hohmann, A. & Frase, R. (1992). Analysis of swimming speed and energy
metabolism in competitive water polo games. in MacLaren J.
E., Reilly T., Lees A., (eds) Biomechanics and Medicine in Swimming,
313-19, N Spon, London.
Kjendlie P. L. & Stallmann R. K. (2008). Drag characteristics of competitive
swimming children and adults. Journal of Applied Biomechanics,
24(1), 35-42.
Pinnington, H. C., Dawson, B. & Blanksby, B. A. (1987). Cardiorespiratory
responses of water polo players performing the head-in-thewater
and the head-out-the-water front crawl swimming technique.
The Australian Journal of Science and Medicine in Sport, 19(1), 15-19.
Platanou, T. & Geladas, N. (2006). The influence of game duration and
playing position on intensity of exercise during match-play in elite
water polo players. Journal of Sports Science, 24(11), 1173-81.
Rodriguez, F. A. (1994). Physiological testing of swimmers and water
polo players in Spain. in Miyashita M., Mutoh Y., Richardson A.B.,
(eds) Medicine and Science in Aquatic Sports, 172-77, Karger, Basel.
Rudic, R., D’Ottavio, S., Bonifazi, M., Alippi, B., Gatta, G. & Sardella,
F. (1999). Il modello funzionale nella pallanuoto. La Tecnica del Nuoto
26, 21-24.
86
Comparison of Combinations of Vectors to define the
Plane of the Hand in order to calculate the Attack
Angle during the Sculling Motion
Gomes, l.e. 1 , Melo, M.o. 1 , la torre, M. 1 , loss, J.F. 1
1 Federal University of Rio Grande do Sul, Porto Alegre, Brazil
Studies into swimming propulsion describe different combinations of
vectors to define the hand plane, which may alter the attack angle. The
study aims (i) to verify the agreement between the attack angles calculated
using different combinations of vectors, described in the literature
and proposed by this study, to define the plane of the hand and (ii) to
verify the variation in vector length of the methods found to be agreement
in order to establish which method is most recommended when
estimating the attack angle during sculling motion. The methods of calculating
attack angles used from the literature and the one proposed
by this study are in agreement. The variation in vector lengths of the
proposed method was smaller than in the other vectors. We recommend
using the proposed method to calculate the attack angle when analyzing
this movement.
Key words: swimming, synchronized swimming, propulsion
IntroductIon
Propulsion is one of the key factors determining performance in human
competitive swimming. However, as yet, this phenomenon is not
fully understood and research to determine propulsive forces exerted
by swimmers’ hands and arms has been strictly experimental. In this
experimental research, studies into propulsion have been based on quasisteady
analyses, which depend on the assumption that the flow under
steady conditions (constant velocity, constant attack and sweepback
angles) is comparable to the flow during the actual swimming stroke.
Quasi-steady analysis involves the following steps: (1) measuring
the lift and drag forces acting on model hands in an open-water channel
or in a wind tunnel for a wide range of hand orientations and, then
calculating the lift and drag coefficients for each condition; (2) recording
an underwater action of a swimmer using three-dimensional filming to
determine the path, velocity and orientation of the hand relative to the
water (attack and sweepback angles); (3) combining the results from
steps 1 and 2 to determine the lift and drag forces using hydrodynamic
equations.
Thus, in order to estimate hand forces in actual swimming, it is
necessary to define the plane of the hand using landmarks to calculate
attack angle during underwater action of a swimmer, since the attack
angle is defined as the angle between the plane of the hand and the
velocity vector of the hand (Payton and Bartlett, 1995). Unfortunately,
problems may arise during this procedure, such as errors derived from
the digitizing procedure, since the hand is hard to accurately digitize,
because it is small and landmarks are placed close together (Payton and
Bartlett, 1995).
From these arguments, Lauder at al. (2001) established the accuracy
and reliability of current and newly proposed procedures for the reconstruction
of hand velocity, sweepback and attack angles from underwater
three-dimensional video analysis. They suggested that a greater distance
between the landmarks would be beneficial in reducing errors arising from
the digitizing procedure. Thus, five additional combinations of vectors
were identified in order to define the plane of the hand. They have suggested
that their proposed method, ‘Lauder 1’, improves accuracy when
measuring the sweepback angle and, more importantly, the attack angle.
However, there are a number of untested possible combinations that may
be used to define the plane of the hand. Moreover, in order to achieve their
purposes, Lauder et al. (2001) used a full-scale mechanical arm capable
of simulating a controlled and highly repeatable underwater phase of the