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Joint Rotations (joint + rotation)
Selected AbstractsMuscle moment arms of the gibbon hind limb: implications for hylobatid locomotionJOURNAL OF ANATOMY, Issue 4 2010Anthony J. Channon Abstract Muscles facilitate skeletal movement via the production of a torque or moment about a joint. The magnitude of the moment produced depends on both the force of muscular contraction and the size of the moment arm used to rotate the joint. Hence, larger muscle moment arms generate larger joint torques and forces at the point of application. The moment arms of a number of gibbon hind limb muscles were measured on four cadaveric specimens (one Hylobates lar, one H. moloch and two H. syndactylus). The tendon travel technique was used, utilizing an electro-goniometer and a linear voltage displacement transducer. The data were analysed using a technique based on a differentiated cubic spline and normalized to remove the effect of body size. The data demonstrated a functional differentiation between voluminous muscles with short fascicles having small muscle moment arms and muscles with longer fascicles and comparatively smaller physiological cross-sectional area having longer muscle moment arms. The functional implications of these particular configurations were simulated using a simple geometric fascicle strain model that predicts that the rectus femoris and gastrocnemius muscles are more likely to act primarily at their distal joints (knee and ankle, respectively) because they have short fascicles. The data also show that the main hip and knee extensors maintain a very small moment arm throughout the range of joint angles seen in the locomotion of gibbons, which (coupled to voluminous, short-fascicled muscles) might help facilitate rapid joint rotation during powerful movements. [source] Enhanced flexor tendon healing through controlled delivery of PDGF-BBJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 9 2009Stavros Thomopoulos Abstract A fibrin/heparin-based delivery system was used to provide controlled delivery of platelet derived growth factor BB (PDGF-BB) in an animal model of intrasynovial flexor tendon repair. We hypothesized that PDGF-BB, administered in this manner, would stimulate cell proliferation and matrix remodeling, leading to improvements in the sutured tendon's functional and structural properties. Fifty-six flexor digitorum profundus tendons were injured and repaired in 28 dogs. Three groups were compared: (1) controlled delivery of PDGF-BB using a fibrin/heparin-based delivery system; (2) delivery system carrier control; and (3) repair- only control. The operated forelimbs were treated with controlled passive motion rehabilitation. The animals were euthanized at 7, 14, and 42 days, at which time the tendons were assessed using histologic (hyaluronic acid content, cellularity, and inflammation), biochemical (total DNA and reducible collagen crosslink levels), and biomechanical (gliding and tensile properties) assays. We found that cell activity (as determined by total DNA, collagen crosslink analyses, and hyaluronic acid content) was accelerated due to PDGF-BB at 14 days. Proximal interphalangeal joint rotation and tendon excursion (i.e., tendon gliding properties) were significantly higher for the PDGF-BB-treated tendons compared to the repair-alone tendons at 42 days. Improvements in tensile properties were not achieved, possibly due to suboptimal release kinetics or other factors. In conclusion, PDGF-BB treatment consistently improved the functional but not the structural properties of sutured intrasynovial tendons through 42 days following repair. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res [source] Neurorehabilitation of Upper Extremities in Humans with Sensory-Motor ImpairmentNEUROMODULATION, Issue 1 2002Dejan B. Popovic PhD Abstract Today most clinical investigators agree that the common denominator for successful therapy in subjects after central nervous system (CNS) lesions is to induce concentrated, repetitive practice of the more affected limb as soon as possible after the onset of impairment. This paper reviews representative methods of neurorehabilitation such as constraining the less affected arm and using a robot to facilitate movement of the affected arm, and focuses on functional electrotherapy promoting the movement recovery. The functional electrical therapy (FET) encompasses three elements: 1) control of movements that are compromised because of the impairment, 2) enhanced exercise of paralyzed extremities, and 3) augmented activity of afferent neural pathway. Liberson et al. (1) first reported an important result of the FET; they applied a peroneal stimulator to enhance functionally essential ankle dorsiflexion during the swing phase of walking. Merletti et al. (2) described a similar electrotherapeutic effect for upper extremities; they applied a two-channel electronic stimulator and surface electrodes to augment elbow extension and finger extension during different reach and grasp activities. Both electrotherapies resulted in immediate and carry-over effects caused by systematic application of FET. In studies with subjects after a spinal cord lesion at the cervical level (chronic tetraplegia) (3,5) or stroke (6), it was shown that FET improves grasping and reaching by using the following outcome measures: the Upper Extremity Function Test (UEFT), coordination between elbow and shoulder movement, and the Functional Independence Measure (FIM). Externally applied electrical stimuli provided a strong central sensory input which could be responsible for the changes in the organization of impaired sensory-motor mechanisms. FET resulted in stronger muscles that were stimulated directly, as well as exercising other muscles. The ability to move paralyzed extremities also provided awareness (proprioception and visual feedback) of enhanced functional ability as being very beneficial for the recovery. FET contributed to the increased range of movement in the affected joints, increased speed of joint rotations, reduced spasticity, and improved functioning measured by the UEFT, the FIM and the Quadriplegia Index of Function (QIF). [source] Interaction of pre-programmed control and natural stretch reflexes in human landing movementsTHE JOURNAL OF PHYSIOLOGY, Issue 3 2002Martin J. N. McDonagh Pre-programmed mechanisms of motor control are known to influence the gain of artificially evoked stretch reflexes. However, their interaction with stretch reflexes evoked in the context of unimpeded natural movement is not understood. We used a landing movement, for which a stretch reflex is an integral part of the natural action, to test the hypothesis that unpredicted motor events increase stretch reflex gain. The unpredicted event occurred when a false floor, perceived to be solid, collapsed easily on impact, allowing the subjects to descend for a further 85 ms to a solid floor below. Spinal stretch reflexes were measured following solid floor contact. When subjects passed through the false floor en route to the solid floor, the amplitude of the EMG reflex activity was double that found in direct falls. This was not due to differences in joint rotations between these conditions. Descending pathways can modify H- and stretch-reflex gain in man. We therefore manipulated the time between the false and real floor contacts and hence the time available for transmission along these pathways. With 30 ms between floors, the enhancement of the reflex was extinguished, whereas with 50 ms between floors it reappeared. This excluded several mechanisms from being responsible for the doubling of the reflex EMG amplitude. It is argued that the enhanced response is due to the modulation of reflex gain at the spinal level by signals in descending pathways triggered by the false platform. The results suggest the future hypothesis that this trigger could be the absence of afferent signals expected at the time of false floor impact and that salient error signals produced from a comparison of expected and actual sensory events may be used to reset reflex gains. [source] Visual and non-visual control of landing movements in humansTHE JOURNAL OF PHYSIOLOGY, Issue 1 2001Marco Santello 1The role of vision in controlling leg muscle activation in landing from a drop was investigated. Subjects (n= 8) performed 10 drops from four heights (0.2, 0.4, 0.6 and 0.8 m) with and without vision. Drop height was maintained constant throughout each block of trials to allow adaptation. The aim of the study was to assess the extent to which proprioceptive and vestibular information could substitute for the lack of vision in adapting landing movements to different heights. 2At the final stages of the movement, subjects experienced similar peak centre of body mass (CM) displacements and joint rotations, regardless of the availability of vision. This implies that subjects were able to adapt the control of landing to different heights. The amplitude and timing of electromyographic signals from the leg muscles scaled to drop height in a similar fashion with and without vision. 3However, variables measured throughout the execution of the movement indicated important differences. Without vision, landings were characterised by 10 % larger ground reaction forces, 10 % smaller knee joint rotations, different time lags between peak joint rotations, and more variable ground reaction forces and times to peak CM displacement. 4We conclude that non-visual sensory information (a) could not fully compensate for the lack of continuous visual feedback and (b) this non-visual information was used to reorganise the motor output. These results suggest that vision is important for the very accurate timing of muscle activity onset and the kinematics of landing. [source] | ||||||||||