Papers by Amanda Silvatti
ISBS-Conference Proceedings Archive, Nov 9, 2009
One critical aspect to 3D reconstruction of human motion using videogrammetry is related to the n... more One critical aspect to 3D reconstruction of human motion using videogrammetry is related to the need for an accurate calibration of large volumes. Most of calibration methods used in biomechanics requires the construction, transportation and measurement of rigid structures and this is more difficult when larger volumes are involved. Recently, alternative approaches have been proposed to overcome this critical aspect (Cerveri et al., 1998; Zhang, 2000). This work presents preliminary results of the proposition and evaluation of a ...
This work aimed to verify if swimmers present better chest wall coordination during breathing tha... more This work aimed to verify if swimmers present better chest wall coordination during breathing than healthy non-athletes analyzing the correlation between ribs motion and the variation of thoracoabdominal volumes. The results of two up-to-date methods based on videogrammetry were correlated in this study. The first one measured the volumes of 4 separate compartments of the chest wall (superior thorax, inferior thorax, superior abdomen and inferior abdomen) as a function of time. The second calculated the rotation angle of the 2nd to the 10th ribs around the quasi-transversal axis also in function of time. The chest wall was represented by 53 markers, attached to the ribs, vertebrae, thorax and abdomen of 15 male swimmers and of 15 non- athletes. A kinematical analysis system equipped with 6 digital video cameras (60Hz) was used to obtain the 3D coordinates of the markers. Correlating the curves of ribs rotation angles with the curves of the separate volumes, swimmers presented higher values than non-athletes when the superior and inferior abdomen were considered and the highest correlation values were found in swimmers for the inferior thorax. These results suggest a better coordination between ribs motion and thoracoabdominal volumes in swimmers, indicating the prevalent and coordinated action of the diaphragm and abdominal muscles to inflate and deflate the chest wall. The results further suggest that swimming practice leads to the formation of an optimized breathing pattern and can partially explain the higher lung volumes found in these athletes reported in literature.
A novel method based on kinematical analysis is proposed to describe the three-dimensional motion... more A novel method based on kinematical analysis is proposed to describe the three-dimensional motion of the ribs during breathing. The three-dimensional coordinates of markers on the ribs and vertebrae were used to calculate the orientation of the ribs as a function of time. A test measured the relative motion between the markers and the ribs using magnetic resonance and the results revealed that the skin motion artifact found for the ribs (absolute mean value 3.9 mm) would induce maximum errors of 4° on rib motion calculation. The method identified a signal coherent with the breathing cycle for the angles of the ribs around the mediolateral axis and was also able to show differences between healthy nonathletes and swimmers, which presented greater angular variation of the ribs (p < .05). In conclusion, this study has shown the reliability of using three-dimensional kinematic analysis to evaluate the movement of the ribs during breathing as well as its potential to identify differences in the behavior of the rib motion in trained swimmers and untrained healthy subjects.
Journal of Strength and Conditioning Research, 2013
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Journal of Sports Sciences, 2012
Journal of Biomechanics, 2012
The purpose of this study was to compare three camera calibration approaches applied to underwate... more The purpose of this study was to compare three camera calibration approaches applied to underwater applications: (1) static control points with nonlinear DLT; (2) moving wand with nonlinear camera model and bundle adjustment; (3) moving plate with nonlinear camera model. The DVideo kinematic analysis system was used for underwater data acquisition. The system consisted of two gen-locked Basler cameras working at 100 Hz, with wide angle lenses that were enclosed in housings. The accuracy of the methods was compared in a dynamic rigid bar test (acquisition volume-4.5 Â 1 Â 1.5 m 3 ). The mean absolute errors were 6.19 mm for the nonlinear DLT, 1.16 mm for the wand calibration, 1.20 mm for the 2D plate calibration using 8 control points and 0.73 mm for the 2D plane calibration using 16 control points. The results of the wand and 2D plate camera calibration methods were less associated to the rigid body position in the working volume and provided better accuracy than the nonlinear DLT. Wand and 2D plate camera calibration methods presented similar and highly accurate results, being alternatives for underwater 3D motion analysis.
Computer Methods in Biomechanics and Biomedical Engineering, 2013
In this study we aim at investigating the applicability of underwater 3D motion capture based on ... more In this study we aim at investigating the applicability of underwater 3D motion capture based on submerged video cameras in terms of 3D accuracy analysis and trajectory reconstruction. Static points with classical direct linear transform (DLT) solution, a moving wand with bundle adjustment and a moving 2D plate with Zhang&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s method were considered for camera calibration. As an example of the final application, we reconstructed the hand motion trajectories in different swimming styles and qualitatively compared this with Maglischo&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s model. Four highly trained male swimmers performed butterfly, breaststroke and freestyle tasks. The middle fingertip trajectories of both hands in the underwater phase were considered. The accuracy (mean absolute error) of the two calibration approaches (wand: 0.96 mm - 2D plate: 0.73 mm) was comparable to out of water results and highly superior to the classical DLT results (9.74 mm). Among all the swimmers, the hands&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; trajectories of the expert swimmer in the style were almost symmetric and in good agreement with Maglischo&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s model. The kinematic results highlight symmetry or asymmetry between the two hand sides, intra- and inter-subject variability in terms of the motion patterns and agreement or disagreement with the model. The two outcomes, calibration results and trajectory reconstruction, both move towards the quantitative 3D underwater motion analysis.
Computer Methods in Biomechanics and Biomedical Engineering, 2013
This study aimed at assessing the applicability of a robust method to determine and correct lens ... more This study aimed at assessing the applicability of a robust method to determine and correct lens distortion before using the direct linear transformation (DLT) algorithm in three-dimensional motion analysis. The known length of a rigid bar was reconstructed under different conditions of working volume (interpolation or extrapolation), number of cameras (2 or 4), position of the cameras (wide or narrow angle between optical axes), camera focal distance (4 or 8 mm) and number of control points (CPs; 8, 12, 18 or 162), through four different camera set-ups. The accuracy (percent root mean square error) of Set-up 2 (non-extrapolated working volume; two cameras; 4 mm focal distance; narrow optical axes angle) decreased with less CPs (162: 0.73%; 8: 2.78%). Set-up 1 (non-extrapolated working volume; two cameras; 8 mm focal distance; wide optical axes angle), Set-up 3 (Set-ups 1 and 2 used simultaneously) and Set-up 4 (extrapolated working volume; two cameras; 4 mm focal distance; wide optical axes angle) showed minor differences in accuracy across groups of CPs, with maximum values of 0.84%, 1.20% and 1.71%, respectively. Random errors were the main source of decreased accuracy of Set-ups 2 and 4.The proposed procedure enables accurate results with no modification in the DLT-based analysis system, even with smaller calibration frames, less CPs and wide field-of-view cameras.
ISBS-Conference Proceedings Archive, Jul 19, 2011
The purpose of this study was to compare two nonlinear camera calibration methods for 3D underwat... more The purpose of this study was to compare two nonlinear camera calibration methods for 3D underwater motion analysis. The DVideo kinematic analysis system was used for underwater online data acquisition. The system consisted of two gen-locked Basler cameras working at 100Hz, with wide angle lenses that were enclosed in housings. The accuracy of both methods was compared in a dynamic rigid bar test. The mean absolute errors were 1.16 mm for wand calibration, 1.20 mm for 2D plane calibration using 8 control ...
ISBS-Conference Proceedings Archive, Jul 22, 2012
The purpose of this study was to investigate the effects of object position in the working volume... more The purpose of this study was to investigate the effects of object position in the working volume on the accuracy of 3D reconstruction, using four different camera calibration approaches: 1) the classical DLT, 2) the nonlinear DLT, 3) the 2D plate and 4) the wand calibration. The DVideo kinematic analysis system was used for underwater data acquisition. The system consisted of two gen-locked Basler cameras (100 Hz) enclosed in housings. A dynamic rigid bar test (acquisition volume-4.5? 1? 1.5 m3) was used to obtain ...
Proc of XI Congresso …, Jan 1, 2005
This work aims to use the 3-D kinematical analysis to evaluate respiratory motion patterns in swi... more This work aims to use the 3-D kinematical analysis to evaluate respiratory motion patterns in swimmers during respiratory maneuvers. Using a kinematics analysis system (Dvideow) with 6 digital video cameras, 30 markers attached on the rib cage and 2 on the pelvis were reconstructed in the 3D space. A previously defined method of analysis was applied in a group of 13 male swimmers (SG) and a control group (CG) of 10 non-athletes volunteers during tidal volume (TV) and vital capacity (VC) maneuvers in sitting position. From the 3D coordinates of the markers, it was obtained time evolution of three joint angles (Euler angles). The highest variation was found in the angle representing the rib rotation around the quasitransverse axis. Differences were found between the groups (p<0.05) considering the correlation coefficient of the angles curves, where SG presented highest values. The results suggest that swimming leads to an optimized respiratory pattern and showed the feasibility of using the 3-D kinematical analysis to evaluate rib cage motion patterns during breathing.
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Papers by Amanda Silvatti