Swing Phase (swing + phase)

Distribution by Scientific Domains


Selected Abstracts


The intertarsal joint of the ostrich (Struthio camelus): Anatomical examination and function of passive structures in locomotion

JOURNAL OF ANATOMY, Issue 6 2009
Nina U. Schaller
Abstract The ostrich (Struthio camelus) is the largest extant biped. Being flightless, it exhibits advanced cursorial abilities primarily evident in its characteristic speed and endurance. In addition to the active musculoskeletal complex, its powerful pelvic limbs incorporate passive structures wherein ligaments interact with joint surfaces, cartilage and other connective tissue in their course of motion. This arrangement may enable energy conservation by providing joint stabilisation, optimised limb segment orientation and automated positioning of ground contact elements independently of direct muscle control. The intertarsal joint is of particular interest considering its position near the mid-point of the extended limb and its exposure to high load during stance with significant inertial forces during swing phase. Functional-anatomical analysis of the dissected isolated joint describes the interaction of ligaments with intertarsal joint contours through the full motion cycle. Manual manipulation identified a passive engage-disengage mechanism (EDM) that establishes joint extension, provides bi-directional resistance prior to a transition point located at 115° and contributes to rapid intertarsal flexion at toe off and full extension prior to touch down. This effect was subsequently quantified by measurement of intertarsal joint moments in prepared anatomical specimens in a neutral horizontal position and axially-loaded vertical position. Correlation with kinematic analyses of walking and running ostriches confirms the contribution of the EDM in vivo. We hypothesise that the passive EDM operates in tandem with a stringently coupled multi-jointed muscle-tendon system to conserve the metabolic cost of locomotion in the ostrich, suggesting that a complete understanding of terrestrial locomotion across extinct and extant taxa must include functional consideration of the ligamentous system. [source]


Clinical Application of Peroneal Nerve Stimulator System Using Percutaneous Intramuscular Electrodes for Correction of Foot Drop in Hemiplegic Patients

NEUROMODULATION, Issue 4 2006
Yoichi Shimada MD
Abstract Objective., To assess the orthotic effect of a functional electrical stimulation device (Akita Heel Sensor System; AHSS) in the treatment of hemiplegic gait with foot drop. Materials and Methods., In the AHSS, a heel sensor is attached to a small plastic heel brace, and the peroneal nerve is stimulated via percutaneous intramuscular electrodes. During the swing phase of the hemiplegic gait, the common peroneal nerve is stimulated by the AHSS. Eight patients in chronic stages of hemiplegia participated in this study. Walking speeds and step cadences on a 10-m course were compared between walking with stimulation and walking without stimulation. Results., Mean walking speed (± SD) was 0.50 ± 0.26 m/sec without stimulation and 0.64 ± 0.31 m/sec with stimulation. The mean percentage increase in walking speed with stimulation was 30.1%. Mean step cadence was 31 ± 7 steps/10 m without stimulation and 27 ± 7 steps/10 m with stimulation. By correcting foot drop, the AHSS significantly increased walking speed and decreased cadence (p < 0.05). Conclusion., The AHSS can significantly improve walking in hemiplegic patients with foot drop. [source]


Neurorehabilitation of Upper Extremities in Humans with Sensory-Motor Impairment

NEUROMODULATION, Issue 1 2002
Dejan 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]


Age- and gender-related changes in the temporal-spatial characteristics of forwards and backwards gaits

PHYSIOTHERAPY RESEARCH INTERNATIONAL, Issue 3 2003
Dr Yocheved Laufer Head
Abstract Background and Purpose Backward walking is used increasingly as a rehabilitation technique for individuals with neurological and orthopaedic impairments. The purpose of the present study was to examine changes in the temporal-spatial characteristics of gait resulting from walking backwards as opposed to forwards, and to determine age and gender effects on these changes. Method Thirty young and 40 aged, independently functioning, subjects were asked to walk forwards and backwards across a computer-based walkway system, providing data on gait velocity, stride length, cadence, swing phase and double support phase. Subjects were divided into groups based on age (young and old) and gender, and each subject was tested under two walking conditions (forwards and backwards). Five temporal-spatial gait parameters were evaluated separately as a function of the three independent variables, with the walking condition repeated for each subject. Results Backwards ambulation is characterized by a slower velocity, shorter stride length and an increased double support phase in both young and older adults. These changes were significantly greater in the older subjects, among whom the swing phase was also decreased. Cadence, however, was not affected by direction of ambulation in either group. The female subjects had a shorter stride length in both movement directions, associated with reduced speed only in backwards ambulation. Conclusions Older individuals are capable of walking backwards for short distances. However, changes in gait characteristics typical to the reversal of movement direction are accentuated with age. These effects must be considered when planning to use backwards ambulation as a rehabilitation technique for older individuals. Copyright © 2003 Whurr Publishers Ltd. [source]


An analysis of simplified muscle activation profile parameterization

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2006
Daniel Strobach
This paper analyzes a simplified method for rough identification of muscle activation profiles of general motor tasks by means of dynamic optimization. Muscle activation profiles are parameterized with six parameters per muscle, using linear combinations of two smooth C, functions closely related to the GAUSSian distribution function used in stochastics and fuzzy control. The method is applied to a simplified subsystem of the human leg consisting of pelvis, thigh shank and foot, interconnected by planar joints at hip, knee and ankle. The system comprises one antagonistic muscle pair at the knee for knee flexion and extension (vastus intermedius and biceps femoris caput brevis). To simulate the swing phase of gait, rheonomic constraints are imposed on pelvis (translation and rotation), hip (rotation) and ankle (rotation). The optimization results show that, (1) the method is suitable to map typical muscle activation time histories that are recorded via EMG, (2) the method can reduce the number of design parameters and CPU-time consumption significantly in comparison to other parameterizations and (3) this reduction in CPU-time consumption additionally coinncides with an improved approximation quality to the target motion. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Sensitivity Analysis of Human Leg Metabolical Costs

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2005
Marko Ackermann
The human walking is characterized by skeletal dynamics and muscle excitation patterns minimizing the metabolical energy. This criterion is applied to assess the performance of lower limb prosthetic devices, and to evaluate therapies for patients presenting gait disorders. It is desirable, therefore, to dispose models of the human normal and pathological gaits capable of estimating the metabolical energy expenditure. For the swing phase of normal and pathological gaits a musculoskeletal model of the lower limb is presented to estimate metabolical energy expenditure. The mechanical model has three degrees of freedom and is actuated by eight Hill-type muscle units, and the model for the metabolical costs is adopted from literature. In this paper a combination of inverse and direct dynamics is used, and a sensitivity analysis of the dynamical behavior and the corresponding metabolical costs estimations with respect to parametrized neural excitations is performed. The leg motions are based on experiments in a gait analysis laboratory. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Visual guidance of the human foot during a step

THE JOURNAL OF PHYSIOLOGY, Issue 2 2005
Raymond F. Reynolds
When the intended foot placement changes during a step, either due to an obstacle appearing in our path or the sudden shift of a target, visual input can rapidly alter foot trajectory. However, previous studies suggest that when intended foot placement does not change, the path of the foot is fixed after it leaves the floor and vision has no further influence. Here we ask whether visual feedback can be used to improve the accuracy of foot placement during a normal, unperturbed step. To investigate this we measured foot trajectory when subjects made accurate steps, at fast and slow speeds, to stationary floor-mounted targets. Vision was randomly occluded in 50% of trials at the point of foot-off. This caused an increase in foot placement error, reflecting lower accuracy and higher variability. This effect was greatest for slow steps. Trajectory heading analysis revealed that visually guided corrections occurred as the foot neared the target (on average 64 mm away). They occurred closer to the target for the faster movements thus allowing less time and space to execute corrections. However, allowing for a fixed reaction time of 120 ms, movement errors were detected when the foot was approximately halfway to the target. These results suggest that visual information can be used to adjust foot trajectory during the swing phase of a step when stepping onto a stationary target, even for fast movements. Such fine control would be advantageous when environmental constraints place limitations on foot placement, for example when hiking over rough terrain. [source]