2D and 3D Motion Analysis
Ruben Mendes
1
Quantitative Evaluation
The objective is analyze the technical gesture headline on the collective sports game that
is Volleyball.
Condition Evaluation
For the evaluation of the technical gesture, the headline that was selected to shoot two
athletes, the first with 61kg of body mass and height of 1.63m and the second with 68.2kg
of body mass and height of 1.75m. It was to asked to athletes who performed the
execution of the technical gesture that with use of upper and lower limbs without balance.
The film camera that was used to film (Sony Cyber-Shot), was put to 3m-site testing and
perpendicular to the movement . The images were captured at 50Hz, in. Mov. Later, the
files were converted to the. Avi in order to be used in motion analysis software: Utilius
fairplay 5. Additionally filmed a calibration system was used (1x2m), as shown in figure 1
and allowing to calibrate the images.
Figure 1. Calibration system adopted.
In the table below the coordinates of the calibration system are presented:
Point X (m) Y (m)
1 0.0 0.0
2 1.0 0.0
2D and 3D Motion Analysis
Ruben Mendes
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3 1.0 2.0
4 0.0 2.0
Results and Discussion
Figure 2. Preparatory phase for implementation of the headline.
We can see that the two athletes (Clara, left image and Dinis, right image) have different
postures at the time before contact with the ball. In the following figures we observe the
main differences.
Figure 3. Projection height of the ball.
2D and 3D Motion Analysis
Ruben Mendes
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I can verify that upon receipt, Dinis throws the ball which is 1.09 meters above the ground,
at the time this image was captured, the Clara is 0.89 meters above the ground. However,
I did not extract these images valid grounds, since the two athletes have different heights
logo, the heights of projection would be different. Thus we verify the projection angle, as
can be seen in the images below.
Figure 4. Angle of the ball.
Through the analysis of the output angle of the ball we can see that the athlete on the right
has a smaller angle than the left logo, it performs the closest desired technical gesture,
since the ball can more protrudes vertically. When designing the ball more vertically and
not horizontally so the athlete can become framed with the ball and that means it hosted
the ball better. Therefore, the athlete from the right was able to perform more accurate and
effective technical gesture, since the ball could best be approved, which is the main
objective of the headline for this study. I will look then where did the athlete won the right
edge over the left.
2D and 3D Motion Analysis
Ruben Mendes
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Figure 5. Forward inclination of the torso and the difference in distance has a foot relative
to each other before the reception of the ball.
We can fix, through these images, the angle of the trunk of Clara (22) is less than the Dinis
(25th), then Dinis has the most stem tilted forward, which will facilitate a better reception to
the ball. Despite being a small difference between the two athletes, I think this difference in
the inclination of the torso will influence the contact with the ball. We can also measure
through the brands present on the gym floor that Dinis have the worry of having a more
advanced foot the other, unlike Clara, which will help in the frame with the ball and a better
reception of the ball, since this orientation of the foot allows the athlete to be more
cautious to change the position if the ball is not well received.
2D and 3D Motion Analysis
Ruben Mendes
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Figure 6. Bending angle of the legs, before receiving the ball.
In this figure, I note that the bending angle of the legs in Dinis is slightly smaller than the
Clara. We believe that this minimal difference between the two athletes, with respect to
bending of the legs cannot be seen as a factor that determined the performance of each
athlete to perform the headline.
References
 Software: Kinovea
 Software: Utilius fairplay