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Joint Position (joint + position)
Terms modified by Joint Position Selected AbstractsA natural redundancy-resolution for 3-D multi-joint reaching under the gravity effectJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 11 2005Masahiro Sekimoto A simple control method for 3-dimensional multi-joint reaching movements under redundancy of degrees of freedom (DOF) is proposed, which need neither introduce any performance index to solve inverse kinematics uniquely nor calculate pseudo-inverse of the Jacobian matrix of task coordinates with respect to joint coordinates. The proposed control signal is composed of linear superposition of three terms: (1) angular-velocity feedback for damping shaping, (2) task-space position error feedback with a single stiffness parameter, and (3) compensation for gravity force on the basis of estimates for uncertain parameters of the potential energy without calculation any inverse joint position to the target in task space. Through a theoretical analysis of the closed-loop dynamics and a variety of computer simulations by using a whole arm model with five DOFs, the importance of synergistic adjustments of damping factors as well as its relation to selection of the stiffness parameter is pointed out. It is shown that if damping factors are chosen synergistically corresponding to the inertia matrix at the initial time and the stiffness parameter then the endpoint converges asymptotically to the target position and reaches it smoothly without incurring any self-motion. © 2005 Wiley Periodicals, Inc. [source] A robot-assisted study of intrinsic muscle regulation on proximal interphalangeal joint stiffness by varying metacarpophalangeal joint positionJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2006Zong-Ming Li Abstract The tightness of intrinsic hand muscles is a common cause of finger joint stiffness. The purposes of this study were to develop a robot-assisted methodology to obtain torque,angle data of a finger joint, and to investigate the regulation of the intrinsic muscles on finger joint stiffness. Our robot system features the integration of a low payload robot arm, a controller, and a force/torque transducer. The system provided highly reproducible torque,angle curves. Torque,angle data of the proximal interphalangeal joint with the metacarpophalangeal joint at 0 and 60 degrees were obtained from eight asymptomatic hands. The torque,angle curve shifted with the position of the metacarpophalangeal joint. As the metacarpophalangeal joint flexion angle changed from 60 to 0 degrees, the equilibrium of the proximal interphalangeal joint increased more than 20 degrees, and joint stiffness increased more than 50%. The dependence of the stiffness of the proximal interphalangeal joint on metacarpophalangeal joint position supports the regulatory role of the intrinsic muscles on finger joint mechanics. This regulatory mechanics is likely amplified in hands with intrinsic muscle tightness, justifying the commonly used Bunnell Intrinsic Tightness Test. © 2005 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:407,415, 2006 [source] The role of M. popliteus in unpredictable and in self-initiated balance provocationsJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2006Ann-Katrin Stensdotter Abstract The purpose of this study was to determine whether m. popliteus (POP) activity would contribute to the control of knee joint position in unpredictable and in self-initiated provocations of standing balance. Ten healthy women (age 25.2,±,4.5 years, means and SD) without known knee pathology were tested for postural reactions (1) to unpredictable support surface translations in anterior and posterior directions, and (2) in self-initiated balance provocations in a reaction time (RT) forward reach-and-grip task. Electromyographic activity was recorded from POP and other leg muscles plus the deltoid muscle. Three-dimensional kinematics were captured for the knee joint and the body centre of mass was calculated. POP was active first of all the muscles recorded, regardless of translation direction, and knee joint movements elicited were either knee extension or external rotation of the tibia. In the RT task, the POP was active after initiation of reaching movement, and there was little consistency in the kinematic response. POP activity was not direction specific in response to support surface translation, but appeared triggered from reactive knee joint movement. The response to the support-surface translation suggests that POP served to control knee joint position rather than posture. In the RT task, we could not deduce whether POP activity was attributed to knee joint control or to postural control. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:524,530, 2006 [source] Accuracy of reproducing hand position when using active compared with passive movementPHYSIOTHERAPY RESEARCH INTERNATIONAL, Issue 2 2001Yocheved Laufer PT PhD Head of Physical Therapy Department Abstract Background and Purpose Evaluating proprioception is relevant to physical rehabilitation because of its significance in motor control. One method of proprioceptive testing involves having subjects either imitate or point at a joint position or movement which was presented via a passive movement. However, as the muscle spindles are subject to central fusimotor control, the proprioceptive system may be better-tuned to movements created by active muscular contraction than to passive movements. The objective of the present study was to determine whether accuracy of reproducing hand position is dependent on whether proprioceptive input is obtained via an active or a passive movement. Method Thirty-nine healthy volunteers (mean age (±SD) 24.6 (±3.6) years) participated in the study. Subjects' right hands, which were obscured from view, were acoustically guided to five targets on a digitizer tablet with either an active or passive upper extremity movement. Subjects were then asked to reproduce the targets' location by either reaching to them with the unseen hand or by use of a laser beam. Distance from target and angular deviations were calculated in both absolute and relative terms. Repeated measures analysis of variance (ANOVA) was performed for each variable followed by predetermined contrasts. Results Comparison between the active and passive conditions when reconstruction of target location was guided kinaesthetically indicates significant differences in absolute distance, range and angular deviation. The comparison when reconstruction of target location was guided visually indicates significant differences in absolute distance, absolute angle and angular deviation. Conclusions The ability to reproduce hand position accurately is enhanced when position is encoded by active upper extremity movement compared with passive movement. The results have implications for the design of strategies for evaluating as well as treating patients with impaired proprioception and limited movement. Copyright © 2001 Whurr Publishers Ltd. [source] Technical note: Forearm pronation efficiency analysis in skeletal remainsAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2009Ignasi Galtés Abstract This work presents an original methodology for analyzing forearm-pronation efficiency from skeletal remains and its variation with regard to changes in the elbow position. The methodology is based on a biomechanical model that defines rotational efficiency as a mathematical function expressing a geometrical relationship between the origin and insertion of the pronator teres. The methodology uses humeral distal epiphysis photography, from which the geometrical parameters for the efficiency calculus can be obtained. Rotational efficiency is analyzed in a human specimen and in a living nonhuman hominoid (Symphalangus syndactylus) for a full elbow extension (180°) and an intermediate elbow position (90°). In both specimens, the results show that this rotational-efficiency parameter varies throughout the entire rotational range and show a dependency on the elbow joint position. The rotational efficiency of the siamang's pronator teres is less affected by flexion of the forearm than that of the human. The fact that forearm-pronation efficiency can be inferred, even quantified, allows us to interpret more precisely the functional and evolutionary significance of upper-limb skeletal design in extant and fossil primate taxa. Am J Phys Anthropol 2009. © 2009 Wiley-Liss, Inc. [source] The ligamentum olecrani of the Elbow Joint in Dogs and CatsANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2005E. Engelke The olecranon ligament (ligamentum olecrani) is described as an elastic ligament of the elbow joint in carnivores that tenses the caudomedial part of the joint capsule. The aim of the study was to compare the course and the microscopic structure of the ligament in dogs and cats. The elbow regions of 25 dogs and 15 cats were dissected to examine the topography of the ligament in extension and flexion. Furthermore, the olecranon ligaments of five dogs and five cats were studied using routine histological methods. Additional sections were stained with Resorcin,Fuchsin and Orcein to detect elastic fibres. In both species the olecranon ligament originates at the lateral surface of the epicondylus medialis humeri and inserts at the cranial crest of the olecranon extending distally to the roof of the processus anconeus. Tension of the ligament only occurs when the elbow joint is flexed maximally. This tension is increased by a slight supination of the forearm, which takes place automatically in this joint position. In dogs the ligament is long (30,40 mm in medium sized breeds) and relatively slim (approx. 2,4 mm). In cats the ligament is short (10,12 mm) and relatively strong (5,8 mm). The histological examination of the olecranon ligament shows all signs of a tight collagenous ligament with a negligible amount of elastic fibres. The olecranon ligament helps to limit the maximal flexion of the elbow joint. In addition, it controls a slight lateral movement of the processus anconeus during the automatic supination of the antebrachial bones in extreme flexion of the elbow joint. [source] Length Dependent Potentiation in Electrically Stimulated Human Ankle Dorsiflexor MusclesNEUROMODULATION, Issue 2 2002Petra Mela PhD Abstract The purpose of this study was to investigate the short-term history effect of a decreasing frequency train on force and the influence of joint angle on such effect in human dorsiflexor muscles. Six able-bodied and three spinal cord injured (SCI) subjects took part in the study. Their isometric left dorsiflexor muscles were stimulated with two-second bursts at three ankle joint positions and movements at the ankle were measured. Trains with constant stimulation frequencies (CSF: 50, 25, 20, 16, 12, 8 Hz) and with decreasing stimulation frequencies (DSF1,2) were used. Each DSF tetanus consisted of four 0.5 second bursts of different frequencies (DSF1: 50, 25, 16, 8 Hz; DSF2: 50, 20, 12, 8 Hz). To evaluate the effect of preceding higher stimulation frequencies (DSF), the average moment at corresponding time intervals in the DSF and CSF trials were compared for 25, 20, 16, 12, 8 Hz. Preceding higher stimulation frequencies caused increase of the moment elicited by a given frequency. This was true for all the subjects at dorsiflexed positions, but the effect is highly dependent on joint ankle. At plantar flexed positions moment enhancement was seen only in SCI subjects. We conclude that effects of joint angle as well as individual muscle properties should be taken into account when optimizing muscle force by means of frequency modulation. [source] | |||||||||||||