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Author Berman, S.; Liebermann, D.G.; McIntyre, J. url  doi
openurl 
  Title Constrained Motion Control on a Hemispherical Surface – Path Planning Type Journal Article
  Year 2014 Publication Journal of Neurophysiology Abbreviated Journal (up) J Neurophysiol  
  Volume 111 Issue 5 Pages 954-968  
  Keywords Constrained motion; geodesics; path planning  
  Abstract Surface-constrained motion, i.e., motion constraint by a rigid surface, is commonly found in daily activities. The current work investigates the choice of hand paths constrained to a concave hemispherical surface. To gain insight regarding the paths and their relationship with task dynamics, we simulated various control policies. The simulations demonstrated that following a geodesic path is advantageous not only in terms of path length, but also in terms of motor planning and sensitivity to motor command errors. These stem from the fact that the applied forces lie in a single plane (that of the geodesic path itself). To test whether human subjects indeed follow the geodesic, and to see how such motion compares to other paths, we recorded movements in a virtual haptic-visual environment from eleven healthy subjects. The task was comprised of point-to-point motion between targets at two elevations (30 degrees and 60 degrees ). Three typical choices of paths were observed from a frontal plane projection of the paths: circular arcs, straight lines, and arcs close to the geodesic path for each elevation. Based on the measured hand paths, we applied k-means blind separation to divide the subjects into three groups and compared performance indicators. The analysis confirmed that subjects who followed paths closest to the geodesic produced faster and smoother movements, compared to the others. The 'better' performance reflects the dynamical advantages of following the geodesic path, as shown by the simulations, and may also reflect invariant features of the control policies used to produce such a surface-constrained motion.  
  Address Ben-Gurion University of the Negev  
  Corporate Author Thesis  
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  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0022-3077 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:24259548 Approved no  
  Call Number Serial 72  
Permanent link to this record
 

 
Author Biess, A.; Liebermann, D.G.; Flash, T. url  doi
openurl 
  Title A computational model for redundant human three-dimensional pointing movements: integration of independent spatial and temporal motor plans simplifies movement dynamics Type Journal Article
  Year 2007 Publication The Journal of Neuroscience : the Official Journal of the Society for Neuroscience Abbreviated Journal (up) J Neurosci  
  Volume 27 Issue 48 Pages 13045-13064  
  Keywords Analysis of Variance; Arm/physiology; Biomechanics; *Computer Simulation; Humans; *Models, Biological; Movement/*physiology; *Nonlinear Dynamics; Posture/physiology; Psychomotor Performance/*physiology; Range of Motion, Articular/physiology; Reaction Time/physiology; Space Perception/*physiology; Time Factors; Torque  
  Abstract Few computational models have addressed the spatiotemporal features of unconstrained three-dimensional (3D) arm motion. Empirical observations made on hand paths, speed profiles, and arm postures during point-to-point movements led to the assumption that hand path and arm posture are independent of movement speed, suggesting that the geometric and temporal properties of movements are decoupled. In this study, we present a computational model of 3D movements for an arm with four degrees of freedom based on the assumption that optimization principles are separately applied at the geometric and temporal levels of control. Geometric properties (path and posture) are defined in terms of geodesic paths with respect to the kinetic energy metric in the Riemannian configuration space. Accordingly, a geodesic path can be generated with less muscular effort than on any other, nongeodesic path, because the sum of all configuration-speed-dependent torques vanishes. The temporal properties of the movement (speed) are determined in task space by minimizing the squared jerk along the selected end-effector path. The integration of both planning levels into a single spatiotemporal representation simplifies the control of arm dynamics along geodesic paths and results in movements with near minimal torque change and minimal peak value of kinetic energy. Thus, the application of Riemannian geometry allows for a reconciliation of computational models previously proposed for the description of arm movements. We suggest that geodesics are an emergent property of the motor system through the exploration of dynamical space. Our data validated the predictions for joint trajectories, hand paths, final postures, speed profiles, and driving torques.  
  Address Department of Mathematics, Weizmann Institute of Science, 76100 Rehovot, Israel. armin.biess@weizmann.ac.il  
  Corporate Author Thesis  
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  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0270-6474 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:18045899 Approved no  
  Call Number Serial 35  
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Author Liebermann, D.G.; Katz, L.; Hughes, M.D.; Bartlett, R.M.; McClements, J.; Franks, I.M. url  doi
openurl 
  Title Advances in the application of information technology to sport performance Type Journal Article
  Year 2002 Publication Journal of Sports Sciences Abbreviated Journal (up) J Sports Sci  
  Volume 20 Issue 10 Pages 755-769  
  Keywords *Biofeedback, Psychology; *Computer Simulation; Humans; Models, Biological; Physical Education and Training/*methods; Psychomotor Performance/physiology; Sports Medicine/methods; *Task Performance and Analysis; Videotape Recording  
  Abstract This paper overviews the diverse information technologies that are used to provide athletes with relevant feedback. Examples taken from various sports are used to illustrate selected applications of technology-based feedback. Several feedback systems are discussed, including vision, audition and proprioception. Each technology described here is based on the assumption that feedback would eventually enhance skill acquisition and sport performance and, as such, its usefulness to athletes and coaches in training is critically evaluated.  
  Address Department of Physical Therapy, Sackler Faculty of Medicine, University of Tel Aviv, Israel  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0264-0414 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:12363293 Approved no  
  Call Number Serial 40  
Permanent link to this record
 

 
Author Issurin, V.B.; Liebermann, D.G.; Tenenbaum, G. url  doi
openurl 
  Title Effect of vibratory stimulation training on maximal force and flexibility Type
  Year 1994 Publication Journal of Sports Sciences Abbreviated Journal (up) J Sports Sci  
  Volume 12 Issue 6 Pages 561-566  
  Keywords Adult; Humans; Male; Muscle Contraction/physiology; Muscle, Skeletal/*physiology; *Physical Education and Training; Vibration/*therapeutic use  
  Abstract In this study, we investigated a new method of training for maximal strength and flexibility, which included exertion with superimposed vibration (vibratory stimulation, VS) on target muscles. Twenty-eight male athletes were divided into three groups, and trained three times a week for 3 weeks in one of the following conditions: (A) conventional exercises for strength of the arms and VS stretching exercises for the legs; (B) VS strength exercises for the arms and conventional stretching exercises for the legs; (C) irrelevant training (control group). The vibration was applied at 44 Hz while its amplitude was 3 mm. The effect of training was evaluated by means of isotonic maximal force, heel-to-heel length in the two-leg split across, and flex-and-reach test for body flexion. The VS strength training yielded an average increase in isotonic maximal strength of 49.8%, compared with an average gain of 16% with conventional training, while no gain was observed for the control group. The VS flexibility training resulted in an average gain in the legs split of 14.5 cm compared with 4.1 cm for the conventional training and 2 cm for the control groups, respectively. The ANOVA revealed significant pre-post training effects and an interaction between pre-post training and 'treatment' effects (P < 0.001) for the isotonic maximal force and both flexibility tests. It was concluded that superimposed vibrations applied for short periods allow for increased gains in maximal strength and flexibility.  
  Address Ribstein Centre for Research and Sport Medicine Sciences, Wingate Institute, Wingate Post, Israel  
  Corporate Author Thesis  
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  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0264-0414 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:7853452 Approved no  
  Call Number Serial 56  
Permanent link to this record
 

 
Author Uri, O.; Pritsch, M.; Oran, A.; Liebermann, D.G. url  doi
openurl 
  Title Upper limb kinematics after arthroscopic and open shoulder stabilization Type Journal Article
  Year 2014 Publication Journal of Shoulder and Elbow Surgery Abbreviated Journal (up) Journal of Shoulder and Elbow Surgery  
  Volume Issue Pages  
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  Series Volume Series Issue Edition  
  ISSN 1058-2746 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 75  
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