- Email: [email protected]
Automatic force plate contact detection protocol for computerized gait analysis
Journal Pre-proof Automatic force plate contact detection protocol for computerized gait analysis Clemens Ambrozy, Stefano Palma, Timothy Hasen¨ohrl, Richard Crevenna
PII:
S0966-6362(19)30537-5
DOI:
https://doi.org/10.1016/j.gaitpost.2019.09.028
Reference:
GAIPOS 7337
To appear in:
Gait & Posture
Received Date:
15 May 2019
Revised Date:
2 September 2019
Accepted Date:
25 September 2019
Please cite this article as: Ambrozy C, Palma S, Hasen¨ohrl T, Crevenna R, Automatic force plate contact detection protocol for computerized gait analysis, Gait and amp; Posture (2019), doi: https://doi.org/10.1016/j.gaitpost.2019.09.028
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.
Automatic force plate contact detection protocol for computerized gait analysis Corresponding author: Dipl.-Ing.(FH) Clemens Ambrozy Medical University of Vienna Department of Physical Medicine, Rehabilitation and Occupational Medicine Währinger Gürtel 18-22 1090 Vienna Austria [email protected]
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Dr. med. univ. Stefano Palma Medical University of Vienna Department of Physical Medicine, Rehabilitation and Occupational Medicine Währinger Gürtel 18-22 1090 Vienna Austria [email protected]
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Mag. Bakk.rer.nat. Timothy Hasenöhrl Medical University of Vienna Department of Physical Medicine, Rehabilitation and Occupational Medicine Währinger Gürtel 18-22 1090 Vienna Austria [email protected]
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Ao.Univ.-Prof. Dr.med.univ. Richard Crevenna MBA MSc Medical University of Vienna Department of Physical Medicine, Rehabilitation and Occupational Medicine Währinger Gürtel 18-22 1090 Vienna Austria [email protected] Highlights:
The developed program runs parallel to the Vicon® data acquisition software. The correct force plate foot contacts are displayed in a graphical user interface. The results of the logical query are written automatically in a tabular file. An automatically generated protocol of the evaluable walks is available. Program eliminates the need for observation over the correct force plate contact.
1. Introduction:
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The computerized gait analysis system uses reflective markers, eight 200 Hz cameras (Vicon®) and two force plates (AMTI®) to collect data, from which the kinetic and kinematic data are then calculated using Nexus® and Polygon®, respectively [1], [2]. For the calculation of the kinetic data, the data of the two force plates embedded in the ground are used. In order to use the data of the force plates for the calculation, the force plates must be contacted correctly. Correct means the complete contact of a plate with one foot, without the second foot partially or completely meeting the same force plate. When assessing the correct force plate foot contact, simple foot and force plate observation is used, and the results are manually entered into a list. Within a measurement, it is likely that several walks will be recorded that are not suitable for the subsequent evaluation since they do not contain correct force plate foot contacts. Algorithms for the detection of gait events are described in several literature [3] [4] [5]. An algorithm describing the correct force plate contact is not found in the literature. A walk is the one-time passage of the measuring volume in one direction. Only those walks that have led to correct force plate foot contact can be used for the evaluation. Ideally, to allow a sufficiently meaningful gait analysis, six correct force plate foot contacts of the left foot and six force plate foot contacts of the right foot are required, which are achieved in six walks [6]. In order to enable automatic logging, a PC program should be created that allows automatic detection and evaluation of the force plate foot contacts and documents the correct force plate foot contacts in a list to help select the relevant walks for the subsequent evaluation.
2. Material and methods:
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Vicon® provided the ViconDatastreemSDK.dotNet® DLL [7], which is integrated into the Microsoft® C# project. This allows simultaneous detection of marker positions and force plate signals during the measurement. The program developed in C# runs in parallel while the Nexus acquisition software is active. The force plates allow - due to the positioning of the force transducer at the vertices of the force plate - the detection of the position curve of the force in the x-y coordinate system, as the centre of pressure (COP) [8]. The plug-in Gait-SACR marker set is used to record the kinematic data [2]. This marker set consists of 15 markers. For each foot, three markers (heel, toe and ankle) are used. Only marker position and the ground reaction forces are necessary for the algorithm. To record the position of the feet within the measurement volume, heel markers and toe markers of both feet are used. Due to the mechanical dimensions of the force plate, the electrical measuring signals of the force plate and the current position of the markers in the measuring volume, it is possible to determine the time and position of the force plate foot contact. Due to the software-based grid division of the two force plates and the simultaneous querying of the marker positions, an individual force plate contact is evaluated as correct or incorrect via a multiple-condition query. In the right angle to the walking direction, the detection area of the force plate is reduced by the software with a distance line to the edge of the force plate. This distance is determined by the distance of the toe marker to the tip of the toe. A detection edge is set to the edge of the force plate, parallel to the walking direction. This distance is defined by the distance of the heel marker to half the foot width. These two parameters are entered into a configuration file. The detection edge of the force plate is chosen so large that the contacts identified as correct by the program are actually correct contacts. On the downside, this large detection edge could lead to the algorithm not detecting a correct force plate contact when the foot contact is close to the edge of the force plate.
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A software-implemented logical query determines the correct force plate contacts. The COP position of the first force plate and the COP position of the second force plate are queried. If the position of the COP is within border, this is used as a single value (COPAMTI1 or COPAMTI2) in the logical query. Furthermore, the position of the heel marker and the position of the toe marker of the right and the left foot, respectively, are queried (RH, RT, LH, LT). Thus, six input parameters are used for the determination. The logical query implemented in the program checks the parameters and checks whether the specified conditions are fulfilled or not. The output of this logical query signals which force plate contact was correct by which foot, for example, left foot AMTI1 (LFA1). If both force plate contacts were correct, this is displayed as “double contact”. The logical query is expressed by the following four equations: LT^LH^COPAMTI1=LFA1; RT^RH^COPAMTI1=RFA1; LT^LH^COPAMTI2=LFA2; RT^RH^COPAMTI2=RFA2. To trigger the acquisition for the logical query, the position of the right heel marker along the walking route is used. The heel marker first passes a zone, 1000 mm before the first force plate, where the capture triggers. After passing another zone, 1000 mm after the second force plate, the capture is stopped. The start and stop event triggered by the heel marker determines the direction of movement. The force plate protocol program runs in parallel with Nexus® gait analysis software. The program provides a graphical user interface (GUI) with following information: the name of the patient or test, the number of registered markers and the number of analogue components. Since there are two force plates and two light barriers, the number of analogue components is four. Both the number of markers and the number of analogue components are simultaneously taken over by the Nexus® software. The parameter “walk” shows the current number of completed walks. The current parameters are also displayed, such as walking direction, force plate contact and current foot. Furthermore, “wait” and “walking” indicate whether the patient is standing or walking. “AMTI1”, “AMTI2” and “Left”, “Right” represent the current number of correct force plate foot contacts. The “Double Contact” parameter displays the number of completed walks that give correct foot contact simultaneously on both force plates.
3. Results:
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The results of the logical query are written automatically in tabular form to a file. The first output parameter describes the index of the performed walk. The second output parameter describes which foot has correct contact with the first force plate listed in the file header. The next parameter describes which foot has correct contact with the second force plate mentioned in the header. In the fourth column, the walking direction arrow of the corresponding walk is entered. In the next column, the time of the completed walk is entered in seconds. In column 6, the correct force plate foot contacts designated as double contact are entered in ascending order. In order to check the objective accuracy of the plate contact, the automatically generated protocols compared with the simultaneously acquired video data of the gait analysis. 1027 Walks with 2054 possible force plate contacts were checked. The algorithm detected 972 plate contacts as correct. The optical control showed that 109 correct plate contacts were not detected by the algorithm. This results in a sensitivity of 89.9%. The algorithm detected 1082 non- or failed force plate contacts. All force plate contacts recognized as correct by the algorithm were actually correct force plate contacts during the optical control. This results in a specificity of 100%.
4. Conclusions:
The force plate protocol program eliminates the need for simultaneous observation and visual control over the quality of the force plate foot contact. Once there is a sufficient number of walks with correct force plate foot contacts, the measurement can be stopped. The automatically generated protocol facilitates the selection of the usable and therefore relevant walks for the measurement, which are then used for the evaluation. The automatic logging of the measurements and the subsequent electronic archiving enables exact documentation of the measurements carried out.
Conflict of interest statement
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The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.
References: [1] Polygon User Manual © Copyright Vicon Motion Systems 1998–2001 Last edited by Lasse Roren on 07/02/02 [2] Plug-in Gait Product Guide – Foundation Notes Vicon Motion Systems, March 2010
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[3] Desailly E1, Daniel Y, Sardain P, Lacouture P. Foot contact event detection using kinematic data in cerebral palsy children and normal adults gait. Gait Posture. 2009 Jan;29(1):76-80. doi: 10.1016/j.gaitpost.2008.06.009. Epub 2008 Aug 3.
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[5] O'Connor CM1, Thorpe SK, O'Malley MJ, Vaughan CL. Automatic detection of gait events using kinematic data. Gait Posture. 2007 Mar;25(3):469-74. Epub 2006 Jul 28.
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[4] Sharenkov A1, Agres AN2, Funk JF3, Duda GN4, Boeth H5. Automatic initial contact detection during overground walking for clinical use. Gait Posture. 2014 Sep;40(4):730-4. doi: 10.1016/j.gaitpost.2014.07.025. Epub 2014 Aug 8.
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[6] EWA SZCZERBIK, MAŁGORZATA KALINOWSKA, The influence of knee marker placement error on evaluation of gait kinematic parameters, Department of Paediatric Rehabilitation, The Children’s Memorial Health Institute, Warszawa, Poland. Acta of Bioengineering and Biomechanics Vol. 13, No. 3, 2011
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[7] Vicon DataStream SDK 1.8.0 Developer’s Guide ©2013-2018 Vicon Motion Systems Limited. Vicon DataStream SDK Developer’s Manual November 2017 For use with Vicon DataStream SDK 1.8.0 and later. Oxford Metrics plc. Vicon Blade™,Vicon Motion Systems is an Oxford Metrics plc company.
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[8] Guillaume M. Meurissea, Frédéric Dierickb, Bénédicte Schepensa, Guillaume J. Bastiena, Determination of the vertical ground reaction forces acting upon individual limbs during healthy and clinical gait, Laboratoire de physiologie et biomécanique de la locomotion, Institute of NeuroScience, Université catholique de Louvain, Louvain-la-Neuve, Belgium
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Figure 1. Example of a correct force plate foot contact (top). Incorrect force plate foot contact (bottom), toe marker is outside of the distance line.
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Figure 2. GUI that displays and counts the correct force plate foot contacts during the measurement acquisition.
Table 1. The correct force plate foot contacts are automatically written to a file. Walk
AMTI2 L L L L
direction > < > <
double time contact 14:17:03 14:17:20 14:17:36 14:17:55
1 2 3 4
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1 2 3 4
AMTI1 R R R R
PII:
S0966-6362(19)30537-5
DOI:
https://doi.org/10.1016/j.gaitpost.2019.09.028
Reference:
GAIPOS 7337
To appear in:
Gait & Posture
Received Date:
15 May 2019
Revised Date:
2 September 2019
Accepted Date:
25 September 2019
Please cite this article as: Ambrozy C, Palma S, Hasen¨ohrl T, Crevenna R, Automatic force plate contact detection protocol for computerized gait analysis, Gait and amp; Posture (2019), doi: https://doi.org/10.1016/j.gaitpost.2019.09.028
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.
Automatic force plate contact detection protocol for computerized gait analysis Corresponding author: Dipl.-Ing.(FH) Clemens Ambrozy Medical University of Vienna Department of Physical Medicine, Rehabilitation and Occupational Medicine Währinger Gürtel 18-22 1090 Vienna Austria [email protected]
-p
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Dr. med. univ. Stefano Palma Medical University of Vienna Department of Physical Medicine, Rehabilitation and Occupational Medicine Währinger Gürtel 18-22 1090 Vienna Austria [email protected]
lP
re
Mag. Bakk.rer.nat. Timothy Hasenöhrl Medical University of Vienna Department of Physical Medicine, Rehabilitation and Occupational Medicine Währinger Gürtel 18-22 1090 Vienna Austria [email protected]
Jo
ur
na
Ao.Univ.-Prof. Dr.med.univ. Richard Crevenna MBA MSc Medical University of Vienna Department of Physical Medicine, Rehabilitation and Occupational Medicine Währinger Gürtel 18-22 1090 Vienna Austria [email protected] Highlights:
The developed program runs parallel to the Vicon® data acquisition software. The correct force plate foot contacts are displayed in a graphical user interface. The results of the logical query are written automatically in a tabular file. An automatically generated protocol of the evaluable walks is available. Program eliminates the need for observation over the correct force plate contact.
1. Introduction:
-p
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The computerized gait analysis system uses reflective markers, eight 200 Hz cameras (Vicon®) and two force plates (AMTI®) to collect data, from which the kinetic and kinematic data are then calculated using Nexus® and Polygon®, respectively [1], [2]. For the calculation of the kinetic data, the data of the two force plates embedded in the ground are used. In order to use the data of the force plates for the calculation, the force plates must be contacted correctly. Correct means the complete contact of a plate with one foot, without the second foot partially or completely meeting the same force plate. When assessing the correct force plate foot contact, simple foot and force plate observation is used, and the results are manually entered into a list. Within a measurement, it is likely that several walks will be recorded that are not suitable for the subsequent evaluation since they do not contain correct force plate foot contacts. Algorithms for the detection of gait events are described in several literature [3] [4] [5]. An algorithm describing the correct force plate contact is not found in the literature. A walk is the one-time passage of the measuring volume in one direction. Only those walks that have led to correct force plate foot contact can be used for the evaluation. Ideally, to allow a sufficiently meaningful gait analysis, six correct force plate foot contacts of the left foot and six force plate foot contacts of the right foot are required, which are achieved in six walks [6]. In order to enable automatic logging, a PC program should be created that allows automatic detection and evaluation of the force plate foot contacts and documents the correct force plate foot contacts in a list to help select the relevant walks for the subsequent evaluation.
2. Material and methods:
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ur
na
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re
Vicon® provided the ViconDatastreemSDK.dotNet® DLL [7], which is integrated into the Microsoft® C# project. This allows simultaneous detection of marker positions and force plate signals during the measurement. The program developed in C# runs in parallel while the Nexus acquisition software is active. The force plates allow - due to the positioning of the force transducer at the vertices of the force plate - the detection of the position curve of the force in the x-y coordinate system, as the centre of pressure (COP) [8]. The plug-in Gait-SACR marker set is used to record the kinematic data [2]. This marker set consists of 15 markers. For each foot, three markers (heel, toe and ankle) are used. Only marker position and the ground reaction forces are necessary for the algorithm. To record the position of the feet within the measurement volume, heel markers and toe markers of both feet are used. Due to the mechanical dimensions of the force plate, the electrical measuring signals of the force plate and the current position of the markers in the measuring volume, it is possible to determine the time and position of the force plate foot contact. Due to the software-based grid division of the two force plates and the simultaneous querying of the marker positions, an individual force plate contact is evaluated as correct or incorrect via a multiple-condition query. In the right angle to the walking direction, the detection area of the force plate is reduced by the software with a distance line to the edge of the force plate. This distance is determined by the distance of the toe marker to the tip of the toe. A detection edge is set to the edge of the force plate, parallel to the walking direction. This distance is defined by the distance of the heel marker to half the foot width. These two parameters are entered into a configuration file. The detection edge of the force plate is chosen so large that the contacts identified as correct by the program are actually correct contacts. On the downside, this large detection edge could lead to the algorithm not detecting a correct force plate contact when the foot contact is close to the edge of the force plate.
lP
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A software-implemented logical query determines the correct force plate contacts. The COP position of the first force plate and the COP position of the second force plate are queried. If the position of the COP is within border, this is used as a single value (COPAMTI1 or COPAMTI2) in the logical query. Furthermore, the position of the heel marker and the position of the toe marker of the right and the left foot, respectively, are queried (RH, RT, LH, LT). Thus, six input parameters are used for the determination. The logical query implemented in the program checks the parameters and checks whether the specified conditions are fulfilled or not. The output of this logical query signals which force plate contact was correct by which foot, for example, left foot AMTI1 (LFA1). If both force plate contacts were correct, this is displayed as “double contact”. The logical query is expressed by the following four equations: LT^LH^COPAMTI1=LFA1; RT^RH^COPAMTI1=RFA1; LT^LH^COPAMTI2=LFA2; RT^RH^COPAMTI2=RFA2. To trigger the acquisition for the logical query, the position of the right heel marker along the walking route is used. The heel marker first passes a zone, 1000 mm before the first force plate, where the capture triggers. After passing another zone, 1000 mm after the second force plate, the capture is stopped. The start and stop event triggered by the heel marker determines the direction of movement. The force plate protocol program runs in parallel with Nexus® gait analysis software. The program provides a graphical user interface (GUI) with following information: the name of the patient or test, the number of registered markers and the number of analogue components. Since there are two force plates and two light barriers, the number of analogue components is four. Both the number of markers and the number of analogue components are simultaneously taken over by the Nexus® software. The parameter “walk” shows the current number of completed walks. The current parameters are also displayed, such as walking direction, force plate contact and current foot. Furthermore, “wait” and “walking” indicate whether the patient is standing or walking. “AMTI1”, “AMTI2” and “Left”, “Right” represent the current number of correct force plate foot contacts. The “Double Contact” parameter displays the number of completed walks that give correct foot contact simultaneously on both force plates.
3. Results:
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The results of the logical query are written automatically in tabular form to a file. The first output parameter describes the index of the performed walk. The second output parameter describes which foot has correct contact with the first force plate listed in the file header. The next parameter describes which foot has correct contact with the second force plate mentioned in the header. In the fourth column, the walking direction arrow of the corresponding walk is entered. In the next column, the time of the completed walk is entered in seconds. In column 6, the correct force plate foot contacts designated as double contact are entered in ascending order. In order to check the objective accuracy of the plate contact, the automatically generated protocols compared with the simultaneously acquired video data of the gait analysis. 1027 Walks with 2054 possible force plate contacts were checked. The algorithm detected 972 plate contacts as correct. The optical control showed that 109 correct plate contacts were not detected by the algorithm. This results in a sensitivity of 89.9%. The algorithm detected 1082 non- or failed force plate contacts. All force plate contacts recognized as correct by the algorithm were actually correct force plate contacts during the optical control. This results in a specificity of 100%.
4. Conclusions:
The force plate protocol program eliminates the need for simultaneous observation and visual control over the quality of the force plate foot contact. Once there is a sufficient number of walks with correct force plate foot contacts, the measurement can be stopped. The automatically generated protocol facilitates the selection of the usable and therefore relevant walks for the measurement, which are then used for the evaluation. The automatic logging of the measurements and the subsequent electronic archiving enables exact documentation of the measurements carried out.
Conflict of interest statement
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The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.
References: [1] Polygon User Manual © Copyright Vicon Motion Systems 1998–2001 Last edited by Lasse Roren on 07/02/02 [2] Plug-in Gait Product Guide – Foundation Notes Vicon Motion Systems, March 2010
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[3] Desailly E1, Daniel Y, Sardain P, Lacouture P. Foot contact event detection using kinematic data in cerebral palsy children and normal adults gait. Gait Posture. 2009 Jan;29(1):76-80. doi: 10.1016/j.gaitpost.2008.06.009. Epub 2008 Aug 3.
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[5] O'Connor CM1, Thorpe SK, O'Malley MJ, Vaughan CL. Automatic detection of gait events using kinematic data. Gait Posture. 2007 Mar;25(3):469-74. Epub 2006 Jul 28.
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[4] Sharenkov A1, Agres AN2, Funk JF3, Duda GN4, Boeth H5. Automatic initial contact detection during overground walking for clinical use. Gait Posture. 2014 Sep;40(4):730-4. doi: 10.1016/j.gaitpost.2014.07.025. Epub 2014 Aug 8.
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[6] EWA SZCZERBIK, MAŁGORZATA KALINOWSKA, The influence of knee marker placement error on evaluation of gait kinematic parameters, Department of Paediatric Rehabilitation, The Children’s Memorial Health Institute, Warszawa, Poland. Acta of Bioengineering and Biomechanics Vol. 13, No. 3, 2011
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[7] Vicon DataStream SDK 1.8.0 Developer’s Guide ©2013-2018 Vicon Motion Systems Limited. Vicon DataStream SDK Developer’s Manual November 2017 For use with Vicon DataStream SDK 1.8.0 and later. Oxford Metrics plc. Vicon Blade™,Vicon Motion Systems is an Oxford Metrics plc company.
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[8] Guillaume M. Meurissea, Frédéric Dierickb, Bénédicte Schepensa, Guillaume J. Bastiena, Determination of the vertical ground reaction forces acting upon individual limbs during healthy and clinical gait, Laboratoire de physiologie et biomécanique de la locomotion, Institute of NeuroScience, Université catholique de Louvain, Louvain-la-Neuve, Belgium
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Figure 1. Example of a correct force plate foot contact (top). Incorrect force plate foot contact (bottom), toe marker is outside of the distance line.
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Figure 2. GUI that displays and counts the correct force plate foot contacts during the measurement acquisition.
Table 1. The correct force plate foot contacts are automatically written to a file. Walk
AMTI2 L L L L
direction > < > <
double time contact 14:17:03 14:17:20 14:17:36 14:17:55
1 2 3 4
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1 2 3 4
AMTI1 R R R R