1 TÜRKİYE PROFESYONEL LİGLERİNDE GÖREV ... - Spor Bilim

obtained as 2.5007(m/sec)sec. This result can be obtained from the mathematical model when
k is taken as 10.45 kg/m. This modification of the drag coefficient is in agreement with
b
Martin et al. [4] who also needed to reduce k b from 30 to 13 kg/m to obtain reasonble results.
The necessity of using a much smaller k b than that measured in passive thowing can be
explained by the fact that the arms contribute to passive drag but are propulsive elements in
active swimming which could greatly reduce the swimmer's effective drag coeeficient [4].
Conclusion
Tether Force (N)
50
40
30
20
10
0
0.0 1.0 2.0 3.0 4.0 5.0 6.0
Time (s)
Mathematical
model
Experiment
Figure 5. Tether force versus time obtained from the experiments
and the mathematical model for f = 0.33 sec -1
In this study, a three dimensional mathematical model is developed for crawl stroke
swimming. Using the basic dynamic relations, the equation of motion is derived and solved
numerically. In order to check the performance of the mathematical model, the numerical
results are compared with the results of the two experiments. The average values of the tether
force of the model for two selected stroke rates are close to those of the tether force
experiments. The results of the free swimming experiments for normal style were found to be
close to the predictions of the model. The proposed model does not consider the leg action,
skin friction and uplift force. The first two of these three forces does not have much effect on
the stroke as compared with drag forces. The effect of uplift force on the strike is more
pronounced while the arm is entering the water. In a real stroke, the arm angles and
frequencies change during the arm pull. This more complex action having different arm
angles at different periods of arm pull together with variable frequencies can be modelled by
the proposed modelling technique easily. For further studies on modelling the crawl stroke,
mathematical models considering the propulsive effect of lift, overlapping strokes and action
of legs are suggested. The patterns of the motions of the body segments should be defined in