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|Title: ||Computer simulation of crawl arm stroke|
|Authors: ||Eid, Hussein M.H.|
|Issue Date: ||1988|
|Publisher: ||© HMH Eid|
|Abstract: ||A four segment model of the crawl arm stroke is developed and validated. The
construction of a theoretical model is discussed in a number of progressive stages. First,
discussion is focussed on a basic two segment model; second, on a linearly configured
simple three segment model; third, on the same model extended by introducing hand angle
changes: then fourth, on modification of the forearm-hand configuration and on the effects
of progressive lateral displacements changing as a functionofnormalised cycle time.
Validation is sought from the start in a step-by-step process in which a physical
model of the arm, first as a one and then a two segment system, is designed. built and
tested in parallel. Thus, during the early stages of development, the behaviour of the
physical model can be used to check the computer simulation of the theoretical model.
Subsequently, as the theoretical model is extended to a four segment system, its
validation is achieved by comparison with a series of experimental observations of five
highly skilled competitive crawl-stroke swimmers. Film analysis procedures are developed
to establish the velocities, lift, drag and total propulsive forces acting on, or generated
from the arm and body segments. These parameters are obtained from an analysis of the
digitized coordinates of eight body landmarks from two camera views. The two cameras are
used with the aid of specially designed open plan periscopes for underwater filming. The
initial values of the measured parameters from film are then incorporated into the model and
the output values of the simulation are compared with the swimmers actual performances to
establish the accuracy of the theoretical model.
The comparison use of the theoretical model and the physical model results in a
range of error between 6% and 30% for the total force and 6% and 11% for the body velocity. The comparison of the theoretical model and film analysis results in maximum
error of 12% for the body velocity and 18% for the total propulsive force.
Simulations of the crawl arm stroke during the underwater phase provide examples
of the procedure. The examples illustrate the value of such simulations in that quantitative
results are obtained which can be used to alter and improve performance.
Considerable changes in the total force occur when the force acting on the hand is
related to the angle of attack and to the rate at which the angle is altered. A maximum
increase of 18% in the total force is obtained when the hand isorientated at 20 degrees to the
horizontal on entry compared with an increase of only 14% at 40 degrees. During
mid-stroke an entty angle of 10 degrees inaeases total force by 16%. The difference
between maximum and minimum peak velocity is 19% when angles increase from 10 to
40 degrees on entry. The body velocity is found to increase by 25% if the input power is
increased by 30%.
The hand is able to deliver about 46% to 63% of the total propulsive force, the
forearm is found to contribute by 28%. and the upper arm by about 2O%. Within limits a
5% change in hand size results in about a 1.6% change in velocity. A maximumin increase of
0.15% in body velocity is obtained as a result of a gradual increase followed by a gradual
decreases of the hand angle of pitch, 0.72% as a result of modifying the forearm lateral
movement and 2.6% as a result of combined modification.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Sport, Exercise and Health Sciences)|
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