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A new era in the capture of human movement; markerless capture of human movement
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Journal o f Biomechanics 2006, Vol. 39 (Suppl 1)
results becomes an important issue for the players. In the present study, we examined 3 basketball players of different skill levels with 126 clean shots from 21 systematically arranged positions to the basket for each player. The angular kinematic data of lower limbs (LL) and upper limbs (UL) were derived from a 3-D motion capture system "PhaseSpace" using 480Hz sampling rate. A 3-D regression analysis on the 3 lower joints (L J) and the 3 upper joints (U J) peak angular velocity showed higher linear relations among the LJ (mean r2 =0.66) than the UJ (mean r2 =0.07). Further examination of the spatial relation between every 2 joint angles for the UJ and the LJ showed similar results: UJ relations were more variable than their LJ counterpart, and further away from the basket more variability was observed in the UL relations. We conclude that the LL performed a more consistent movement pattern in providing the basic support and strength for the shooting movement whereas the more variable UL movement controls the performance accuracy. The movement degeneracy of the basketball clean shot resides largely in the UL, especially in the coordination between elbow and wrist movements.
6.7. New Trends in Movement Analysis 7452 Fr, 11:00-11:45 (P51 ) A new era in the capture of human movement: markerless capture of human movement T.P. Andriacchi, L. Muendermann, S. Corazza, A. Chaudhari. Stanford
University, Stanford, CA, USA This work was motivated in part by the potential for markerless motion capture to explore new and important research applications for the study of human movement. Most common methods for accurate capture of three-dimensional human motion require a laboratory environment and the attachment of markers or fixtures to the body's segments. These laboratory conditions can cause unknown experimental artifacts. Thus, our understanding of normal and pathological human movement would be enhanced by a method that allows the capture of human movement without the constraint of markers or fixtures placed on the body. In this paper, the advancement of markerless human motion capture is described in the context of biomechanical applications. The role of choosing appropriate technical equipment and algorithms for accurate markerless motion capture is explored systematically. As an example, the feasibility of accurately and precisely measuring 3D human body kinematics for the lower limbs using a markerless motion capture system on the basis of visual hulls is demonstrated. The markerless framework established in this study can serve as a basis for developing the broader application of markerless motion capture. Each of the modules can be independently evaluated and modified as newer methods become available, thus making markerless motion capture a feasible and practical alternative to marker based systems. The method will be illustrated with specific applications to studies of normal and pathological human locomotion. In conclusion, a viable and feasible method for markerless motion capture for clinical and biomechanical applications has been developed. The ease of use, accuracy and capacity to measure unencumbered movement of this markerless motion capture method will greatly expand the potential applications of the study of human locomotion and could lead to a new era in our understanding of the complexity of human movement. 7242 Fr, 11:45-12:00 (P51) Describing the motion of the lower limbs using inverse kinematics N. Bogaert 1, T. De Wilde 1, C. Forausberger 1, J. Vander Sloten 1, G. Van der Perre 1, B. Haex 1, H. Bruyninckx 2 . 1Division of Biomechanics and Engineering
Design, Katholieke Universiteit Leuven, Heverlee, Belgium, 2Division of Production Engineering, Machine Design & Automation, Katholieke Universiteit Leuven, Heverlee, Belgium Introduction: Existing gait analysis systems use skin markers to analyze patient motion. Recently developed marker-free systems (based on optical surface measurements) avoid soft-tissue interference and the time consuming attachment of the markers by highly qualified personnel. The marker information however needs to be replaced by other (model-) information. The goal of this study is to show that the technique of inverse kinematics can reduce the number of marker points. Measurements and Methods:A standard two-dimensional 3 DOF and a 3D 6 DOF forward kinematical model of the lower limbs have been developed. Kinematical parameters and motion information were obtained from existing measurement data. Motion data from several motions has been used as input to the inverse kinematics algorithm by applying the motion of one toe marker relatively to the pelvis reference coordinate system. The inverse kinematics then computes then estimates the marker positions of the intermediate points. Results: The simulated motions of the different marker points are compared to their respective initial (modeled) measurement data from the marker motion. Within the sagittal plane, the two-dimensional and three-dimensional models both highly correspond to the marker motion. At knee-level, an accuracy of
Oral Presentations less than 20 mm can be reached. The results also show the two-dimensional model can function as initial estimation for the three-dimensional model, which is a more accurate approximation of the underlying anatomical structure, but the stability depends highly on the initial estimation. Discussion and Conclusion: This study shows inverse kinematics is able to partially replace measurement data from surface markers without high accuracy loss. As a consequence nearly the same results can be obtained, using less surface marker information. However, to compare these results to real data, dynamic measurements of the skeletal movement (using MRI/RX) are necessary. 6116 Fr, 12:00-12:15 (P51) Tibio-femoral motion: new insights from in vivo measurement D.L. Benoit 1, D.K. Ramsey 2, M. Lamontagne 3, L. Xu 3, P. Wretenberg 4, P. Renstrem 5. 1Department of Mechanical Engineering and 2Department
of Physical Therapy, University of Delaware, Newark DE, USA, 3School of Human Kinetics, University of Ottawa, Ottawa, Canada, 4Section of Orthopaedics and 5Section of Sports Medicine, Karolinska University Hospital, Stockholm, Sweden Introduction: Knee joint motion during gait has often been described in textbooks and the literature however in vivo tibiofemoral rotations and translation during gait in healthy knees is limited to a database of only 7 subjects. The purposes of this study were to measure in vivo tibiofemoral motion during gait and characterize the non-sagittal plane rotations and translations in healthy young adults. Methods: Six healthy male subjects had intra-cortical bone pins inserted into the proximal tibia and distal femur. Reflective markers were attached to each bone pin and to the skin of the tibia and thigh respectively. RSA was used to determine the anatomical reference frames of the tibia and femur. Knee joint motion was recorded during walking using infra-red cameras at 120Hz. The kinematics derived from the bone-pin were used to describe the rotations of the knee and compared to the skin markers. Results and discussion: The antero/posterior translation of the tibia relative to the femur during stance was 6.5±3.6 mm. Our study confirms that for a given knee flexion angle there may be more than one tibio-femoral position. This uncoupling was observed for internal/external rotation and antero/posterior translations. At 150 knee flexion (20% and 85% stance) the tibia was 20 internally rotated or 30 externally rotated respectively, while the tibia was positioned at 2.5 or 0 mm anterior respectively. Conclusions: The secondary rotations and translation excursions of the knee joint are smaller than those described using skin markers or found in the literature. Due to differential uncoupling of the secondary motions of the knee, ensemble averaging of gait data during stance may mask individual subject gait characteristics.
6034 Fr, 12:15-12:30 (P51) Neuromuscular control of the hamstrings to protect the acl: in v/vo experimentation M. Lamontagne 1,3, A. Caraffa2,3, G. Cerulli 2,3. 1University of Ottawa, Ottawa,
Canada, 2University Hospital of Perugia, Perugia, Italy, 3Biomechanics Laboratory, Let People Move, Perugia, Italy From a clinical perspective investigations of ligament and tendon loading are essential to gain insight into injury mechanism and may lead to the prevention of injuries. Several in vivo strain studies have provided insight into the biomechanical function of ligaments but have offered limited information for activities involving neuromuscular control. Only few investigations have investigated the in vivo ACL mechanical behaviour during dynamic motions such as the jump, quick stop, and cut (Benoit et al., 2000; Beynnon and Fleming, 1998; Cerulli et al., 2003; Fleming et al., 1999). However, the direct relationship between ACL elongation and neuromuscular control of the knee joint flexor and extensor muscles has not been well investigated and remains unclear. We present a biomechanical approach to address neuromuscular control of the hamstrings to protect the ACL through in vivo experimentation using direct measurement methods. The objective consisted of investigating the relationship between in-vivo ACL strain and neuromuscular control of the Hamstrings during jumping, stopping, and cutting movements. This investigation has confirmed that the stopping, jumping and cutting manoeuvres generate a relatively high level of ACL elongation that initiates at or just before foot contact when the leg is most extended. The anticipatory contraction of the hamstring and gastrocnemius muscles may play an important role in protecting excessive ACL elongation whereas the quadriceps muscle prevent the collapsing of the knee joint after the foot impact with the ground. This article has demonstrated the benefits of using in vivo experimentation that yielded useful information that could not have been found without direct measurement.
Journal o f Biomechanics 2006, Vol. 39 (Suppl 1)
results becomes an important issue for the players. In the present study, we examined 3 basketball players of different skill levels with 126 clean shots from 21 systematically arranged positions to the basket for each player. The angular kinematic data of lower limbs (LL) and upper limbs (UL) were derived from a 3-D motion capture system "PhaseSpace" using 480Hz sampling rate. A 3-D regression analysis on the 3 lower joints (L J) and the 3 upper joints (U J) peak angular velocity showed higher linear relations among the LJ (mean r2 =0.66) than the UJ (mean r2 =0.07). Further examination of the spatial relation between every 2 joint angles for the UJ and the LJ showed similar results: UJ relations were more variable than their LJ counterpart, and further away from the basket more variability was observed in the UL relations. We conclude that the LL performed a more consistent movement pattern in providing the basic support and strength for the shooting movement whereas the more variable UL movement controls the performance accuracy. The movement degeneracy of the basketball clean shot resides largely in the UL, especially in the coordination between elbow and wrist movements.
6.7. New Trends in Movement Analysis 7452 Fr, 11:00-11:45 (P51 ) A new era in the capture of human movement: markerless capture of human movement T.P. Andriacchi, L. Muendermann, S. Corazza, A. Chaudhari. Stanford
University, Stanford, CA, USA This work was motivated in part by the potential for markerless motion capture to explore new and important research applications for the study of human movement. Most common methods for accurate capture of three-dimensional human motion require a laboratory environment and the attachment of markers or fixtures to the body's segments. These laboratory conditions can cause unknown experimental artifacts. Thus, our understanding of normal and pathological human movement would be enhanced by a method that allows the capture of human movement without the constraint of markers or fixtures placed on the body. In this paper, the advancement of markerless human motion capture is described in the context of biomechanical applications. The role of choosing appropriate technical equipment and algorithms for accurate markerless motion capture is explored systematically. As an example, the feasibility of accurately and precisely measuring 3D human body kinematics for the lower limbs using a markerless motion capture system on the basis of visual hulls is demonstrated. The markerless framework established in this study can serve as a basis for developing the broader application of markerless motion capture. Each of the modules can be independently evaluated and modified as newer methods become available, thus making markerless motion capture a feasible and practical alternative to marker based systems. The method will be illustrated with specific applications to studies of normal and pathological human locomotion. In conclusion, a viable and feasible method for markerless motion capture for clinical and biomechanical applications has been developed. The ease of use, accuracy and capacity to measure unencumbered movement of this markerless motion capture method will greatly expand the potential applications of the study of human locomotion and could lead to a new era in our understanding of the complexity of human movement. 7242 Fr, 11:45-12:00 (P51) Describing the motion of the lower limbs using inverse kinematics N. Bogaert 1, T. De Wilde 1, C. Forausberger 1, J. Vander Sloten 1, G. Van der Perre 1, B. Haex 1, H. Bruyninckx 2 . 1Division of Biomechanics and Engineering
Design, Katholieke Universiteit Leuven, Heverlee, Belgium, 2Division of Production Engineering, Machine Design & Automation, Katholieke Universiteit Leuven, Heverlee, Belgium Introduction: Existing gait analysis systems use skin markers to analyze patient motion. Recently developed marker-free systems (based on optical surface measurements) avoid soft-tissue interference and the time consuming attachment of the markers by highly qualified personnel. The marker information however needs to be replaced by other (model-) information. The goal of this study is to show that the technique of inverse kinematics can reduce the number of marker points. Measurements and Methods:A standard two-dimensional 3 DOF and a 3D 6 DOF forward kinematical model of the lower limbs have been developed. Kinematical parameters and motion information were obtained from existing measurement data. Motion data from several motions has been used as input to the inverse kinematics algorithm by applying the motion of one toe marker relatively to the pelvis reference coordinate system. The inverse kinematics then computes then estimates the marker positions of the intermediate points. Results: The simulated motions of the different marker points are compared to their respective initial (modeled) measurement data from the marker motion. Within the sagittal plane, the two-dimensional and three-dimensional models both highly correspond to the marker motion. At knee-level, an accuracy of
Oral Presentations less than 20 mm can be reached. The results also show the two-dimensional model can function as initial estimation for the three-dimensional model, which is a more accurate approximation of the underlying anatomical structure, but the stability depends highly on the initial estimation. Discussion and Conclusion: This study shows inverse kinematics is able to partially replace measurement data from surface markers without high accuracy loss. As a consequence nearly the same results can be obtained, using less surface marker information. However, to compare these results to real data, dynamic measurements of the skeletal movement (using MRI/RX) are necessary. 6116 Fr, 12:00-12:15 (P51) Tibio-femoral motion: new insights from in vivo measurement D.L. Benoit 1, D.K. Ramsey 2, M. Lamontagne 3, L. Xu 3, P. Wretenberg 4, P. Renstrem 5. 1Department of Mechanical Engineering and 2Department
of Physical Therapy, University of Delaware, Newark DE, USA, 3School of Human Kinetics, University of Ottawa, Ottawa, Canada, 4Section of Orthopaedics and 5Section of Sports Medicine, Karolinska University Hospital, Stockholm, Sweden Introduction: Knee joint motion during gait has often been described in textbooks and the literature however in vivo tibiofemoral rotations and translation during gait in healthy knees is limited to a database of only 7 subjects. The purposes of this study were to measure in vivo tibiofemoral motion during gait and characterize the non-sagittal plane rotations and translations in healthy young adults. Methods: Six healthy male subjects had intra-cortical bone pins inserted into the proximal tibia and distal femur. Reflective markers were attached to each bone pin and to the skin of the tibia and thigh respectively. RSA was used to determine the anatomical reference frames of the tibia and femur. Knee joint motion was recorded during walking using infra-red cameras at 120Hz. The kinematics derived from the bone-pin were used to describe the rotations of the knee and compared to the skin markers. Results and discussion: The antero/posterior translation of the tibia relative to the femur during stance was 6.5±3.6 mm. Our study confirms that for a given knee flexion angle there may be more than one tibio-femoral position. This uncoupling was observed for internal/external rotation and antero/posterior translations. At 150 knee flexion (20% and 85% stance) the tibia was 20 internally rotated or 30 externally rotated respectively, while the tibia was positioned at 2.5 or 0 mm anterior respectively. Conclusions: The secondary rotations and translation excursions of the knee joint are smaller than those described using skin markers or found in the literature. Due to differential uncoupling of the secondary motions of the knee, ensemble averaging of gait data during stance may mask individual subject gait characteristics.
6034 Fr, 12:15-12:30 (P51) Neuromuscular control of the hamstrings to protect the acl: in v/vo experimentation M. Lamontagne 1,3, A. Caraffa2,3, G. Cerulli 2,3. 1University of Ottawa, Ottawa,
Canada, 2University Hospital of Perugia, Perugia, Italy, 3Biomechanics Laboratory, Let People Move, Perugia, Italy From a clinical perspective investigations of ligament and tendon loading are essential to gain insight into injury mechanism and may lead to the prevention of injuries. Several in vivo strain studies have provided insight into the biomechanical function of ligaments but have offered limited information for activities involving neuromuscular control. Only few investigations have investigated the in vivo ACL mechanical behaviour during dynamic motions such as the jump, quick stop, and cut (Benoit et al., 2000; Beynnon and Fleming, 1998; Cerulli et al., 2003; Fleming et al., 1999). However, the direct relationship between ACL elongation and neuromuscular control of the knee joint flexor and extensor muscles has not been well investigated and remains unclear. We present a biomechanical approach to address neuromuscular control of the hamstrings to protect the ACL through in vivo experimentation using direct measurement methods. The objective consisted of investigating the relationship between in-vivo ACL strain and neuromuscular control of the Hamstrings during jumping, stopping, and cutting movements. This investigation has confirmed that the stopping, jumping and cutting manoeuvres generate a relatively high level of ACL elongation that initiates at or just before foot contact when the leg is most extended. The anticipatory contraction of the hamstring and gastrocnemius muscles may play an important role in protecting excessive ACL elongation whereas the quadriceps muscle prevent the collapsing of the knee joint after the foot impact with the ground. This article has demonstrated the benefits of using in vivo experimentation that yielded useful information that could not have been found without direct measurement.