Biomechanics and Medicine in Swimming XI

BiomechanicsandmedicineinswimmingXi
conclusIon
Effective and safe ways to improve swimmers’ sports results in the process
of training mesocycle are, first of all, connected with decreasing of
unavoidable losses at both stages of metabolic energy transformation
into useful activity result, which is quantitatively reflected in dynamics
of values of mechanical and propulsive efficiency.
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112
Prediction of Propulsive Force Exerted by the Hand
in Swimming
Kudo, s. 1 and lee, M.K. 1
1 Republic Polytechnic, Singapore
The aim of this study was to develop a method to predict propulsive
forces exerted by the hand in swimming based on the pressure distribution
on the hand. Hydrodynamic forces acting on the hand were predicted
using 12 pressure sensors, and the hand direction was determined
by a motion capture system. We combined information to predict the
propulsive forces exerted by the hand during the front crawl stroke. The
proportion of drag and lift forces relative to the propulsive forces was
55% and 45%, respectively. The best-fit equations used to predict hydrodynamic
forces in a previous study may cause errors in the prediction of
hydrodynamic forces acting on the hand due to multicollinearity. Such
errors can be minimized with a lesser order of best-fit equations. In
addition, feedback on the propulsive forces exerted by the hand can be
generated within a few hours.
Key words: pressure, hand kinematics, drag, lift.
IntroductIon
Propulsive force exerted by the hand and hydrodynamic forces acting
on the hand in swimming have been quantified and used to analyze the
technique of swimming strokes (Cappaert et al., 1995; Schleihaulf et al.,
1983; Shleihauf et al., 1988). However, the method to predict hydrodynamic
forces acting on the hand could involve considerable errors as the
effect of hand acceleration and wave drag acting on the model have not
been taken into consideration in previous studies on the prediction of
hydrodynamic forces acting on the hand (Pai and Hay, 1988; Kudo et al.,
2008). Acceleration using a hand model has been taken into account in
linear motion (Sanders, 1999). Errors in the prediction of hydrodynamic
forces on the hand could also result from the time consuming method of
manual digitization of landmarks on the swimmer’s hand from recorded
image taken from multiple points of view (Payton and Bartlett, 1995;
Lauder et al., 2001).
A pressure method was developed to predict hydrodynamic forces
acting on the hand in swimming based on the pressure at 12 points of
the hand surface (Kudo et al., 2008). The study measured hydrodynamic
forces acting on a hand model and pressures on the model surface so as
to develop a best-fit equation to predict hydrodynamic forces acting on
the model. However, a method to predict propulsive forces exerted by
the swimmer’s hand using the pressure method during swimming has
not been developed. Propulsive forces by the hand are useful information
for both swimmer and coach in the analysis of technique in swimming.
Thus, the aim of this study was to develop a method to predict
propulsive forces exerted by the hand using the pressure method during
swimming. This study also considered the hand size of a swimmer in a
best-fit equation because the hand size of a swimmer can be different
from the size of a hand model used in the previous study.
Methods
A swimmer whose hand size was 0.0136 m 2 was asked to swim the front
crawl stroke at sub-maximal effort for 18 m in the swimming pool at
Republic Polytechnic following some light warm up. A right-handed
Cartesian coordinate system was embedded at the bottom of the pool;
the x-direction defined the direction of swimming, the y-direction defined
the side-to-side direction, and the z-direction defined the vertical
direction.
A portable data logger with 12 pressure sensors (MMT, Japan) was