Abstract: Previous studies have reported that patients with Parkinson's disease (PD) show, in the "off medication" state, a reduced activation of tibialis anterior (TA) in the late swing-early stance phase of the gait cycle. In PD patients the pathophysiological picture may cause differences among the stride cycles. Our aims were to evaluate how frequently TA activity is reduced in the late swing-early stance phase and if there is a relationship between the TA pattern and the clinical picture. Thirty PD patients were studied 2 h after Levodopa administration ("on-med") and 12 h after Levodopa wash-out ("off-med"). They were evaluated by the Unified Parkinson's Disease Rating Scale (UPDRS III) and surface electromyography of TA and gastrocnemius medialis (GM). The root mean square (RMS) of the TA activity in late swing-early stance phase (RMS-A) was normalized as a percent of the RMS of the TA activity in late stance-early swing (RMS-B). RMS-A was reduced in 30% of patients in the "off-med" condition. Within these patients, the percentage of stride cycles with reduced RMS-A, ranged between 28% and 83%. After Levodopa intake, no stride cycle showed reduced RMS-A. Patients with reduced RMS-A had a lower UPDRS III total score in the "on-med" rather than in the "off-med" condition (p=0.02). Our data confirm and extend previous observations indicating that, in "off-med" the function of TA is impaired in those patients clinically more responsive to Levodopa. TA activation is reduced in a relatively high percent of gait cycles in the "off-med" state. Since the variability of TA activation disappears after Levodopa administration, this phenomenon could be the expression of an abnormal dopaminergic drive.
Abstract: Standard clinical gait analysis protocols usually limit to test self-selected speed gait: this approach is generally valid and permits time and cost saving. Yet, the literature evidences suggest that some pathologies (especially at onset or subclinical level) may not primarily affect plain gait, but more demanding locomotor tasks. In the present study we therefore propose a multiple-task gait analysis protocol including: self-selected, increased and decreased speed gait; walking on toes; walking on heels; step ascending and step descending, and apply it to 40 healthy subjects (20 aged 6-17, 20 aged 22-72) thus building extensive reference data set. Published studies already report normative data for some of these tasks, but inhomogeneously (due to different collecting methods and biomechanical models, population characteristics, nature of data). We verify a good correlation between our results and those presented by Schwartz et al. (2008) [12] in their study providing extensive data on the effect of walking speed on the gait of healthy children. In discussing the results, the rationale and effectiveness of each task is confirmed, and we supply an electronic addendum with comprehensive kinematic, kinetic and electromyographic normative data for the considered population, along with a set of reference parameters and related statistical analysis, as a premise for further applications on pathological subjects.
Abstract: Charcot-Marie-Tooth (CMT) disease is the most common inherited neuromuscular disorder, presenting with symptoms often occurring since childhood, and showing a progressive course. At present, there are no valid and reliable measures for evaluation of impairment and disability in the pediatric population. The aim of this study was to determine the usefulness of outcome measures, commonly used in adult patients, in CMT children. We report the results of a comprehensive evaluation of 21 children affected with CMT type 1A, including clinical examinations, measure of hand and foot muscle strength with a hand-held dynamometer, and the following scales: CMT Neuropathy Score or its clinical component CMT Examination Score, Overall Neuropathy Limitations Scale (ONLS), Walk-12 questionnaire, and nine-hole peg test (9-HPT). Hand grip, three-point pinch, and foot dorsiflexion strength were significantly lower than age/sex equivalent in almost all cases. 9-HPT was significantly abnormal in 62% of patients and CMT Examination Score was <10 points in all cases. ONLS showed presence of minor disability in the upper limbs in 57% and mild abnormalities of gait in 71% of patients. Overall, these scales demonstrated limited potential to measure disability and severity of the disease confirming that it is necessary to identify specific scales for children with CMT.
Abstract: Approximately 60% of stroke survivors experience hand dysfunction limiting execution of daily activities. Several methods have been proposed to objectively quantify fingers' joints range of motion (ROM), while few studies exist about multi-finger coordination during hand movements. The present work analysed this aspect, by providing a complete characterization of spatial and temporal aspects of hand movement, through the mathematical modelling of multi-joint finger motion in healthy subjects and stroke patients.
Abstract: Some neurodegenerative diseases at early stage may not drastically affect basic gait ability, whereas more demanding locomotor tasks are more prone to disease-induced abnormalities. In this study, we evaluated the interday test-retest reliability, 4-6 weeks apart, of instrumented movement analysis on a group of 20 subjects with Charcot-Marie-Tooth (CMT) disease considering a set of kinematic and kinetic curves and related parameters obtained during natural walking (NW) and faster walking, heel and toe-walking, step ascending and descending. Results showed that the reliability was good for NW, with the exception of trunk curves, pelvic tilt and EMG profiles (moderate reliability), and trunk ROM in sagittal/transverse plane (poor reliability). Comparing our results with literature, CMT patients did not present a greater variability during NW than healthy subjects or patients with diseases of CNS. Additional locomotor tasks showed a slight reduction of reliability, although the moderate-to-good level shown in NW was almost never reduced to poor. Most of SEM values (absolute measurement errors) were smaller than 5°, a clinically acceptable threshold. In particular THS, an ankle joint related parameter computed across heel and toe-walking tasks, showed an optimal reliability (ICC=0.95, SEM=2.7°) and correlation with CMT clinical scores. Toe and heel-walking and step ascending tasks maximised the number of parameters with a moderate-to-good correlation with patients' clinical status. We concluded that, in addition to natural walking, more challenging locomotor tasks are good candidates to provide reliable and sensitive outcome measures for CMT patients.
Abstract: Purpose: The purpose of the study was to compute Virtual Time to Contact (VTC) from stabilometric assessment to study balance impairments in people with multiple sclerosis (PwMS). To this purpose we assessed the ability of VTC to discriminate between balance skills of PwMS and healthy subjects (HS), among sensory conditions and between fallers and non fallers. Methods: VTC was calculated to characterize balance performance in 47 PwMS and 13 HS in four different sensory conditions during quiet standing. Main Outcome Measures were VTC, Number of falls, Berg Balance Scale and Dynamic Gait Index. Results: The results showed that VTC was able to discriminate between PwMS and HS (p < 0.0001) and between challenging sensory conditions (p < 0.0001), no relevant information was added by VTC in the detection of subjects prone to falls. Conclusion: VTC provides unique information with respect to balance control because it takes into account the relationship between centre of mass (CoM) and the borders of base of support (BoS). VTC proved to be a valid descriptor of balance performance in PwMS highlighting balance disorders in this population of subjects, however models for falls prediction have to be improved. [Box: see text].
Abstract: Gait pattern classification may assist in clinical decision making and cluster analysis (CA) has been often adopted to this aim. The goal of this study was to identify, through CA, typical walking patterns in a group of 21 young subjects with CMT1A, a hereditary progressive neuropathy, and to study possible correlation with the disease's clinical status. The protocol included kinematic/kinetic analysis of natural walking and more demanding locomotor tasks, i.e. toe- and heel-walking. Hierarchical cluster analysis was carried out on parameters related to primary signs (foot-drop and push-off deficit) and, separately, to compensatory mechanisms at proximal (pelvis, hip and knee) or distal (ankle) level. CA on primary signs during natural walking identified three clusters: (1) pseudo-normal patients (PN), not significantly different from controls; (2) patients showing only foot-drop (FD); (3) patients with foot-drop and push-off deficit (FD&POD). Patients belonging to the PN subgroup showed distal abnormalities during heel-walking. The FD&POD subgroup was associated to a significantly worse clinical score (CMTES, p<0.05). The main compensatory strategies, which occurred independently from primary clusterization, included augmented hip/knee flexion in swing (steppage) and early ankle plantarflexion at mid stance (vaulting). We concluded that, although a number of young CMT1A patients do not show typical primary deviations during natural walking, they do show significant abnormalities in more demanding locomotor tasks that should be therefore considered. It is also hypothesized that progression of this degenerative condition may be associated to the migration of patients to more severe clusters, with possible appearance of compensatory strategies.
Abstract: A ground reaction based method is proposed to evaluate the hypothesis that a stabilization phase occurs in transitions towards erect posture, following the macroscopic movement and preceding the quiet final erect posture, whose aim is to control and dissipate the residual inertial unbalancing forces occurring at the transition end. The experimental protocol considers three tasks leading to the final erect posture: taking a step forward (F), sit-to-stand (S), and bending the trunk forward (B), The method mainly consists of the fitting of a negative exponential function on the instability time profile following the end of the transition movement. The model parameters Y(0), T, and Y(inf), respectively, quantify the initial instability rate, a time duration related to the stabilization, and the final asymptotic instability rate. Results from a sample of 40 adult able bodied subjects demonstrated that a postural stabilization phase actually occurs: Y(inf) is smaller (0.010, 0.010, and 0.008 m/s(2) for, respectively, F, S, and B tasks) than Y(0) (0.081, 0.137, and 0.057 m/s(2)). Tis in the order of seconds (0.95, 0.51, and 1.00 s). No trial with large values of both Y(0) and T was observed, evidencing that large initial instability rates are quickly controlled and reduced. The Y(0) and T parameters distribution are discussed according to the possible underlying active and/or passive stabilization mechanisms. The test-retest reliability overall figure (mean ICC 0.45 for 12 indexes) increased, when dropping the indexes related to the less reliable B task, to values (mean ICC 0.56 for eight indexes) comparable to published posturographic data.
Abstract: Locomotion studies employ either treadmill (TW) or overground walking (OW), considering that differences between them are negligible. The present study tests this notion by comparing coordination between upper- and lower-limb movements in healthy individuals during OW and TW at matched speeds. Results indicated that TW induced a higher cadence, which highly influenced interlimb coordination, in terms of frequency coupling and relative phase between arm and thigh motion. At low speed, the 2:1 pattern (double arm swing per stride) displayed lower incidence in TW compared to OW, and this was correlated with a lower sagittal acceleration at the shoulders, at twice the stride frequency, in the former condition. The low occurrence of the 2:1 coupling in TW, moreover, was correlated to a preferential adoption of a cadence exceeding 80% of the arm's resonant frequency, whereas higher incidence of this pattern in OW involved a preferential cadence below the 80% threshold. Results indicated also that the relative phase between arm and ipsilateral thigh swinging was smaller in TW, in relation to an earlier occurrence of maximum thigh extension, shortened stance phase, and increased cadence. These findings suggest that arm-leg coordination is different in OW and TW, and that difference can be mainly ascribed to condition-specific setting of central mechanisms for scaling stride frequency, for controlling dynamic axial posture (sagittal shoulder acceleration), and, possibly, for maintaining inter-limb synchrony. Awareness of a different "motor set" in TW and OW is critical if data from the two paradigms are used in physiological and patho-physiological studies.
Abstract: The purpose of this study was to examine the effects of static stretching on leg extensor muscles during squat jump (SJ) at different knee starting angles. Seventeen male subjects (23 +/- 3 years, 179 +/- 5 cm, and 74 +/- 6 kg) performed on a force platform 2 series (preceded or not [control condition] by 10-minute static stretching of quadriceps and triceps surae muscles) of SJs at different knee starting angles: 50 degrees, 70 degrees, 90 degrees, and 110 degrees. Squat jump height, peak force, maximal acceleration, velocity, and power were calculated for each jump. The angle that maximized power development was obtained from the power-angle relationship. The SJ height, peak force, and maximal velocity increased according to angle amplitude in both control and stretching conditions (p < 0.01), performance being significantly lower in the stretching condition (p < 0.01). Peak power was obtained at 90 degrees in both control and stretching conditions, but was significantly lower (p < 0.01) after stretching. These results suggest that an acute bout of static stretching reduces power and force development during SJ, decrements being significantly higher at lower knee starting angles. Therefore, the use of static stretching may be questionable in those power activities requiring maximal power output at knee angles near full extension.
Abstract: The aim of this research was to obtain information concerning muscle fatigue and muscle activation levels by measuring quantitative parameters through the surface electromyographic signal, and use such information to integrate the OCRA (Occupational Repetitive Actions) method for risk assessment of upper limb biomechanical overload Along with the main risk factors associated with the development of work-related upper limb musculoskeletal disorders (UL WMSDs) like posture, movement, frequency of action and organizational factors, this method also takes into account the muscular effort. Unlike the other risk factors that can be directly measured during inspections on farms, muscular effort is currently estimated only via a subjective assessment scale (Borg CR-10 scale).
Abstract: Thirty-nine adult individuals with stroke in the stable phase were asked to walk at their preferred speed and then as fast as possible. A set of gait indexes were computed, including spatial temporal parameters, ankle and hip mechanical work, and timing of ankle push-off onset, for comparison with normal velocity-dependent profiles. Algorithms were used to classify the resulting gait patterns when the patients walked at their preferred speed and fast and to identify the patients' strategies to maximise speed. Patients' strategies were characterised by a variation in the parameters, which were reduced, equal or increased, in relation to normal patterns. At both speeds, stroke individuals tended to walk at higher cadence and with shorter stride length. At the preferred speed the investigated parameters for all patients were mostly within the normal profile (71.8-94.9%). The exception was the finding of positive work at the ankle where 64% of the stroke individuals showed reduced work production. At fast speed (increments to 36%BH/s) fewer patients presented values within the normal profile for all the parameters (17.9-74.4%), with the exception of negative work at the ankle and hip. The parameter variations showed a more consistently abnormal picture. The results indicate that, in order to increase gait speed, patients with hemiparesis have different functional resources on which to draw, and these vary from individual to individual. Thus, gait analysis at different gait speed should be adopted to develop individualised programs that will improve quality of life for the patients.
Abstract: Surface Functional Electrical Stimulation (FES) requires high stimulation voltages. A step-up transformer in the output stage of the stimulation circuit is often used. In the present technical paper a voltage controlled current source (VCCS) is presented as an alternative to the transformer coupling. Two (master-slave) coupled transconductance amplifiers (TAs)--in series with pre-charged capacitors--are used to drive the output current. After each stimulation pulse the capacitors are recharged to a high voltage by a switch mode power supply (SMPS). A multiplexer in the output stage is used to provide biphasic output. Output rise-time (10-90%) was less than 2 micros at 100 mA output. Biphasic charge balanced stimulation current can be produced with a net current to ground of less than 20 nA, thus virtually separated from ground. The circuit permits recording of the volitional myoelectric signal from the stimulated muscle. It is part of a portable myoelectrically controlled FES system powered by 2 AA batteries and currently used in clinical trials.
Abstract: To make a preliminary evaluation of the feasibility of a robot-based rehabilitation protocol for the improvement of upper limb motor co-ordination in a group of patients with multiple sclerosis.
Abstract: Focal dystonia (FD) is a movement disorder that frequently affects instrumental musicians. Distinguishing between primary dystonic movement and secondary compensatory abnormal movement is crucial for the correct treatment of planning in FD. Such distinction is complex in musicians because of the complexity, speed, and small-ness of involved movement. The goal of the current study was to assess the influence of instrumented movement analysis (MA) in treatment decision making in musician's FD. A group of 18 musicians with FD was instrumentally analyzed in an MA laboratory equipped with optoelectronic and electromyographic (EMG) acquisition systems. The muscle(S) primarily responsible for the dystonic movement or posture (trigger muscle) was identified on the basis of clinical assessment alone and, in a second phase, with the additional information provided by instrumented assessment. Comparison between clinical and instrumented assessment outcomes and the subjective rating of found differences were then analyzed. In 67% of patients, instrumental assessment changed the decision made by clinical assessment, indicating identification of a different trigger muscle or allowing for a more specific identification. In 28% of patients, instrumental assessment confirmed the outcome of the clinical assessment, with an increase in the confident level of the clinical decision. The most frequent change was an improved specification of which finger flexor muscle (superficialis or profundus) was triggering the dystonic movement. Although caution is needed due to the non blinded design of the present study, our results suggest that instrumented movement analysis is a useful complementary tool to clinical assessment in treatment planning for musician's focal dystonia-its use might change the identification of the muscles primarily responsible for dystonic movements as well as increase the confidence level of the clinician in treatment decision-making. Med Probl Perform Art 2008;23:99-106.
Abstract: Clinical evidence of impaired arm swing while walking in patients with Parkinson's disease suggests that basal ganglia and related systems play an important part in the control of upper limb locomotor automatism. To gain more information on this supraspinal influence, we measured arm and thigh kinematics during walking in 10 Parkinson's disease patients, under four conditions: (i) baseline (no treatment), (ii) therapeutic stimulation of the subthalamic nucleus (STN), (iii)L-DOPA medication and (iv) combined STN stimulation and L-DOPA. Ten age-matched controls provided reference data. Under baseline conditions the range of patients' arm motion was severely restricted, with no correlation with the excursion of the thigh. In addition, the arm swing was abnormally coupled in time with oscillation of the ipsilateral thigh. STN stimulation significantly increased the gait speed and improved the spatio-temporal parameters of arm and thigh motion. The kinematic changes as a function of gait speed changes, however, were significantly smaller for the upper than the lower limb, in contrast to healthy controls. Arm motion was also less responsive after L-DOPA. Simultaneous deep brain stimulation and L-DOPA had additive effects on thigh motion, but not on arm motion and arm-thigh coupling. The evidence that locomotor automatisms of the upper and lower limbs display uncorrelated impairment upon dysfunction of the basal ganglia, as well as different susceptibility to electrophysiological and pharmacological interventions, points to the presence of heterogeneously distributed, possibly partially independent, supraspinal control channels, whereby STN and dopaminergic systems have relatively weaker influence on the executive structures involved in the arm swing and preferential action on those for lower limb movements. These findings might be considered in the light of phylogenetic changes in supraspinal control of limb motion related to primate bipedalism.
Abstract: Turning whilst walking was investigated by gait analysis in a group of Parkinson's Disease (PD) patients with mild clinical impairment and no significant abnormalities in stride parameters and kinematics of steady-state, linear walking. Comparison with age-matched controls demonstrated that patients approached turns with a slower step and completed turning with a greater number of steps. Moreover, the normal cranio-caudal sequence, whereby rotation of the head toward the intended direction of travel is followed by rotation of the trunk, was replaced by nearly simultaneous rotation of head and trunk and decreased relative head excursion after the second turning step. The evidence of abnormal inter-segmental coordination during turning in mildly affected, normally walking patients suggests that task-specific pathophysiological mechanisms, not necessary related to basic locomotor deficits, underlie disturbed directional changes in PD. Furthermore, turning-related neural systems may be more vulnerable to functional impairments associated with PD, as compared with linear walking. Hierarchically higher control levels involved in the turning ability may explain the observed unexpected association.
Abstract: In a first experiment we studied, through a line bisection task, (a) the frequency of the selective disruption of far or near space representations in a group of 28 right brain-damaged patients and (b) the effect of tool use on line bisection error in far and near space in order to clarify whether the kind of action performed by the subject influences the extension of space representation, as suggested by previous studies. In a second experiment, carried out on two neglect patients, we asked whether the representation of "near" and "far" space depends on the sensory feedback during the execution of the action or whether it is independent on sensory feedback and more related to the action programmed as a consequence of the kind of tool used. Our data show (a) that dissociations between far and near space neglect are a frequent observation in right brain damaged patients and that most of these patients are able to recode space representations when tools change the spatial relation between the agent's body and the target object; (b) that spatial remapping can be elicited by the kind of action associated to the tool used and by the sensory feedback (either visual or proprioceptive) available during the execution of the task. In particular, presence of tactile proprioceptive feedback elicited remapping of far space into near space, whereas absence of visual feedback induced remapping of near space into far space.
Abstract: The impact of electromyographic biofeedback (EMG BFB) applied during functional gait activities and employed in accord with theories on motor learning was investigated in a chronic hemiplegic patient.
Abstract: The cardinal motor symptoms of Parkinson's disease (PD) have been widely investigated with particular reference to abnormalities of steady-state walking. The great majority of studies, however are related to severe forms of PD patients (phases > = 3 of Hoehn and Yahr scale), where locomotor abnormalities are clearly manifested. Goal of the present study was to quantitatively describe locomotor symptoms in subjects with mild PD. Accordingly, a multitask protocol involving instrumental analysis of steady-state linear walking, initiation of gait, and turning while walking was applied to a group of patients with idiopathic PD in their early clinical stage (phases 1 and 2 of Hoehn and Yahr scale), as well as in age-matched elderly controls. Kinematic, kinetic, and myoelectric measures were obtained by optoelectronic motion analysis, force platform, and telemetric electromyography. Results in PD patients showed a tendency to bradykinetic gait, with reduction of walking speed and cadence. Impairments of gait initiation consisted in reduction of the backward shift of the center of pressure (CoP) and prolongation of the stepping phase. Alterations of the turning task were more consistent and included delayed reorientation of the head toward the new direction, altered head-upper trunk rotational strategy, and adoption of a greater number of steps to complete the turning. It is concluded that patients in the early stage of PD reveal mild alterations of steady-state linear walking and more significant anomalies in the transitional conditions, especially during changes in the travel direction. Quantitative analysis of nonstationary locomotor tasks might be a potentially useful starting point for further studies on the pathophysiology of PD.
Abstract: The effects of subthalamic nucleus (STN) stimulation and L-dopa administration on the arm and leg swing movements associated with overground walking were studied in a group of patients with idiopathic Parkinson's disease (PD). Ten patients undergoing deep brain stimulation and twenty controls were tested using 3D kinematic motion analysis. Parkinsonian patients under basal conditions walked more slowly and with reduced arm and leg swing compared to controls. Moreover, they displayed significant impairments of the normal interlimb coordination. Both STN stimulation and L-dopa increased the walking speed and the amplitude of arm and leg swing movements. Additional improvements of the coordination between upper and lower limb were documented by reductions of the phase-shift between arm and ipsilateral leg motion, with displacement toward the control range (perfect counterphase). STN stimulation alone and L-dopa alone produced similar effects on the variables analyzed. The combination of the two treatments, instead, yielded additive effects on the gait speed and a slight increase of the upper and lower limb range of motion, in the absence of further improvements in the inter-segmental coordination. Moreover, whereas the increased arm swing could be accounted by the sole adoption of a higher gait speed, both the increment of the leg movement amplitude and the decreased interlimb phase shift appeared to imply an additional effect, possibly related to the treatment. These results may suggest that differential supraspinal controls operate on the neural networks subserving upper and lower limb motion during human walking.
Abstract: We recently developed a textile-based system for the unobtrusive assessment of vital signs. The system, named MagIC, was originally designed to collect data in elderly people and cardiac patients while living in a confined environment. Extending the area of application of MagIC from clinics to daily life meant to pay particular attention to the garment design and to the amount of intelligence embedded into the system. In this paper we addressed both these issues by illustrating 1) a new methodology we are developing to help the design of smart garments for daily life applications and 2) an example of embedded intelligence developed for an application of MagIC in ergonomics.
Abstract: Playing a musical instrument is a constrained motor activity; the instrument has a fixed geometry and playing technique that the performer must accommodate. Although the performer progressively adapts to the instrument during years of education, few options are available for adapting the instrument to the performer. The present work is intended to quantitatively describe the effects of using different setups of the violin shoulder rest during performance. Three conditions were considered, the maximum and minimum heights allowed by the shoulder rest and the absence of the shoulder rest. The setups allowed a height variation of < 40 mm. Fifteen skilled violin players performed a three-octave scale in G with the three rest setups. An optoelectronic motion capture system measured the positions of passive markers placed on the player's body and on the violin and bow, in order to compute, by means of mathematical models, the kinematics of the body, violin, and bow. The increase in rest height was significantly related to a reduction in head rotation (-7.0 degrees), left shoulder rotation (-8.5 degrees), and left acromion elevation (-17.2 mm) and to an increase in left shoulder flexion (+8.2 degrees) and left forearm pronation (+8.8 degrees). In general, the results demonstrate that a skilled player is able to adapt to any shoulder rest setup and can maintain the quality of sound, and that the adaptations are primarily those of the anatomical systems involved in holding the violin and not in holding the bow. Moreover, adjustment of the shoulder rest setup appears to be the individual's search for a tradeoff position, which possibly may be alleviated by adopting objective assessment and innovative shoulder rests.
Abstract: The effects of subthalamic nucleus (STN) stimulation on the spatio-temporal organization of locomotor commands directed to lower limb muscles were studied in subjects with idiopathic Parkinson's Disease (PD) by recording the EMG activity produced during steady-state walking in representative thigh (rectus femoris, RF, and semimembranosus, SM) and leg (gatrocnemius medialis, GAM, and tibialis anterior, TA) muscles, under four experimental conditions: basal stimulation OFF, unilateral (right and left) stimulation ON, and bilateral stimulation ON. Locomotor profiles of all of the muscles tested were found to be substantially affected by STN stimulation, either in terms of restoration/enhancement of the main activity bursts or normalization of recruitment timing thereof. Responses showed relatively higher statistical significance in the distal groups (GAM and TA) and, within them, for the EMG components called into action over the ground-contact (ankle dorsiflexors) and midstance (ankle plantarflexors) phases of the stride cycle. In line with data obtained from clinical rating, unilateral stimulation produced less consistent EMG changes compared with bilateral stimulation. However, at variance with clinical effects, which prevailed on the side of the body contralateral to stimulation, EMG responses to unilateral stimulation were usually symmetrical. Results indicate that the impact of STN stimulation on locomotor activation of lower limb muscles in PD is characterized by: 1) substantial effects exhibiting differential topographical (distal versus proximal) and stride-phase (stance versus swing) consistency and 2) absence of the lateralized actions typically observed for the clinical signs of the disease. Interaction with the activity of functionally different executive systems might account for the observed pattern of responsiveness.
Abstract: A quantitative and objective method based on the optoelectronic kinematic analysis of hand segments and on the calculation of global and partial parameters, which provide measures of the degree of long finger and thumb extension is proposed for the evaluation of the hand's voluntary range of motion and maximal opening of the fingers and thumb. To test the precision and repeatability of the method, the protocol was applied on 14 healthy subjects (28 hands). The proposed parameters are repeatable and show a precision between 5.5 degrees and 10.4 degrees (mean value: 7.3 degrees), comparable to values obtained with other methods. Advantages of the present approach include simultaneous analysis of all fingers, absence of cumbersome connecting cables and no need for individually customized devices. The method, also applied to the paretic hands of two hemiplegic stroke patients before and after electrical stimulation of the wrist and finger extensor muscles, has shown encouraging results for its clinical feasibility and utility in addition to functional tests.
Abstract: We demonstrated a method for enhancing the tenodesis grip in individuals with sustained tetraplegia at the 6th cervical vertebra neurological level. Subjects used the myoelectric activity from wrist extensor muscles to directly control the electrical stimulation of the extrinsic finger and thumb flexors (flexor pollicis longus and flexor digitorum superficialis/ profondus) with the use of a specially designed system, Myoelectrically Controlled Functional Electrical Stimulation (MeCFES). We screened 20 medical records and selected 9 subjects. Of the nine subjects, five showed a positive response to the surface stimulation and could test the system; the other four failed to achieve functional finger flexion because of skin sensitivity or inadequate movement. We evaluated hand function, with and without the MeCFES system, using tests involving three everyday objects: manipulating a videocassette with the key grip, drinking from a bottle with the palmar grasp, and writing with a pen using the tripod grip. Without the system, none of the five subjects could complete all three tasks; but, when assisted with MeCFES, all subjects completed all the tasks. The system proved simple and intuitively easy to use, and no training was needed for subjects to obtain immediate functionality. We will need further research to evaluate the usefulness of the system in activities of daily living.
Abstract: The effects of subthalamic nucleus (STN) stimulation on the anticipatory postural actions associated with the initiation of gait were studied in ten patients with idiopathic Parkinson's disease undergoing therapeutic deep brain stimulation. Kinematic, dynamic and electromyographic analysis was performed before and while subjects were starting gait in response to an external cue. Effects of STN stimulation on the standing posture preceding the go signal included significant improvement of the vertical alignment of the trunk and shank, decrease of the hip joint moment, backward shift of the center of pressure (CoP) and reduction of abnormal tonic and/or rhythmic activity in the thigh and leg muscles. Responses to bilateral STN stimulation were more consistent than those evoked by unilateral stimulation. Moreover, comparison between postural changes induced by STN stimulation applied prior to the gait initiation cue and during simple quiet standing revealed more significant responses in the former condition. Effects on the actual gait initiation process included shortening of the imbalance phase, larger backward/lateral displacement of CoP and more physiological expression of the underlying anticipatory muscular synergy. Additional changes were shortening of the unloading phase, shortening of the first-swing phase and increase in the length of the first step. Results demonstrate substantial influence of STN stimulation on functionally basic motor control mechanisms. In particular, the evidence of more significant responses upon attention-demanding conditions and the remarkable effects on postural programmes sub-serving feed-forward regulation of the onset of complex multijoint movements, suggests a consistent action on postural sub-systems relying on cognitive data processing and internal models of body mechanics.
Abstract: Several studies have been performed with automatic motion analysis techniques to investigated the locomotor disorders of patients with severe Parkinson's disease (PD). These are mainly related to steady-state walking. Aim of the present study was to investigate the presence and the degree of these disorders in patients at early stages of PD. For this purpose a group of patients with mild PD (H&Y < or =2) and a group of age-matched controls were assessed by means of multifactorial analysis of kinematic and kinetic variables, during the execution of the following motor tasks: steady-state walking, gait initiation and turning around an obstacle. Results showed that PD patients did not differ from controls in steady-state walking, while significant differences emerged in gait initiation and turning strategies. Main differences consisted in a limitation of the amplitude of the imbalance phase and of the first step, and, for the turning task, in a delayed initiation of the turning movement, with an altered head-trunk rotational strategy. It is concluded that patients in early stages of PD do not reveal, during steady state walking, consistent impairments of kinematic and kinetic patterns typical of severe PD patients. Nevertheless, they present significant alterations in transient conditions such as gait initiation and change of walking direction. The above results suggest that a quantitative analysis of locomotor tasks which imply the transition from one condition to another, could provide parameters useful for the characterization of early stage PD patients and, potentially, markers for a precox differential diagnosis respect other neurodegenerative diseases characterized by parkinsonisms.
Abstract: This work is focused on the design of closed-loop controllers for FES-supported standing up and sitting down. This task is a difficult one, due to the lack of stability of the considered system and to its nonlinear dynamic behaviour. In this paper, a control strategy based on two nested control loops is presented. The inner loop is based on a linear PID controller that stabilizes the system. The outer loop is designed using the Virtual Reference Feedback Tuning (VRFT) strategy, that allows a fast and easy tuning of the controller starting from a single I/O data set. Both linear and nonlinear control laws are implemented exploiting the VRFT algorithms. Simulation results show that the proposed technique is effective in controlling a paraplegic patient in FES-based standing up and sitting down. (c) 2004 Elsevier Ltd. All rights reserved.
Abstract: The paper deals with the identification of motor strategies adopted by trans-femoral amputees to compensate for the constraints of hip motion induced by the interference of the socket with the pelvis and, particularly, with the ischial tuberosity. A group of 11 subjects with trans-femoral amputation, three of whom wore two different prostheses, giving a sample size of 14 cases, were studied by gait-analysis protocols: the present paper focuses on the pelvis-thigh kinematics at foot strike. The results showed that, at the prosthetic side, the hip is significantly less flexed and less extended, respectively, at the ipsilateral and contralateral foot strike. Moreover, the pelvis is significantly more anterior tilted at sound foot strike. The anterior step length showed a decreased sound limb anterior step in 12 out of 14 cases. The authors interpret these results as a combination of mechanical constraints and compensatory actions: the reduced prosthetic hip extension is determined by the mechanical constraint involved in the pelvis-socket interference; and the increased pelvis tilt and sound hip flexion occurring at the same time are compensating strategies, adopted by the amputees, in order to obtain a functional step length and symmetrical thigh inclinations. Those factors determine a gait pattern which is functional, only slightly slower than normal gait, and without any perceivable alterations. On the other hand, the authors show that the increased pelvis tilting necessarily overloads the lumbar tract of the spine and may be related to the frequent occurrence of low-back pain in amputee subjects, despite the positive functional gait recovery.
Abstract: The paper deals with the identification of motor strategies adopted by trans-femoral amputees to compensate for the constraints of hip motion induced by the interference of the socket with the pelvis and, particularly, with the ischial tuberosity. A group of 11 subjects with trans-femoral amputation, three of whom wore two different prostheses, giving a sample size of 14 cases, were studied by gait-analysis protocols: the present paper focuses on the pelvis-thigh kinematics at foot strike. The results showed that, at the prosthetic side, the hip is significantly less flexed and less extended, respectively, at the ipsilateral and contralateral foot strike. Moreover, the pelvis is significantly more anterior tilted at sound foot strike. The anterior step length showed a decreased sound limb anterior step in 12 out of 14 cases. The authors interpret these results as a combination of mechanical constraints and compensatory actions: the reduced prosthetic hip extension is determined by the mechanical constraint involved in the pelvis-socket interference; and the increased pelvis tilt and sound hip flexion occurring at the same time are compensating strategies, adopted by the amputees, in order to obtain a functional step length and symmetrical thigh inclinations. Those factors determine a gait pattern which is functional, only slightly slower than normal gait, and without any perceivable alterations. On the other hand, the authors show that the increased pelvis tilting necessarily overloads the lumbar tract of the spine and may be related to the frequent occurrence of low-back pain in amputee subjects, despite the positive functional gait recovery.
Abstract: Subthalamic nucleus (STN) stimulation, a recent surgical approach to Parkinson's disease (PD), has been shown to be effective in relieving motor symptoms. The present study carried out a full body gait analysis, during overground walking, on ten PD patients with bilaterally implanted STN stimulation devices. Walking performance was analyzed on the same day, in four conditions (Stim Off-Med Off, Stim On-Med Off, Stim Off-Med On, Stim On-Med On). The results showed that, on average, STN stimulation alone (S+M-) and L-dopa alone (S-M+), significantly increased gait speed, stride length and the lower limb joint Range of Motion (ROM) with respect to the basal condition (S-M-); also cadence was found to play a role in velocity increase, particularly when L-dopa was administered. Both treatments improved pelvis and trunk kinematics, and power production at the ankle and hip joints. The combination of the two treatments (S+M+) produced an additional effect on gait speed, stride length, ROM of knee and ankle joints, pelvis obliquity and trunk inclination. Given the additive and synergistic effects, it can be hypothesized that the two treatments have different mechanisms of action. Our results confirm the findings of earlier studies that employed treadmill walking.
Abstract: Cerebellar ataxia is a complex motor disturbance that involves the planning and execution of movements and reduces movement accuracy and co-ordination. The quantification of ataxic signs is commonly realised through visual examination of motor tasks performed by the patient and assignment of scores to specific items composing the international co-operative ataxia rating scale (ICARS). The present work studied an experimental procedure to characterise specific aspects of motor disturbances in ataxia objectively. Four tests belonging to the ICARS were considered: walking, knee-tibia test, finger-to-nose and finger-to-finger test. Through a kinematic analysis performed during the above tests, specific indices were defined to quantify velocity, linearity, asymmetry, tremor, instability and smoothness of movement or posture. The procedure was applied to five patients with cerebellar ataxia and to ten healthy adult subjects. Results demonstrated that the patients moved significantly more slowly than the healthy subjects (0.67 against 0.97m s(-1) and 0.81 against 1.02 m s(-1), respectively, for straight walk and finger-to-nose tests) and showed poorer linearity and smoothness behaviour. Velocity, linearity, tremor, smoothness and instability indices showed moderate to good correlation with the corresponding ICARS score. Some of these indices can separately evaluate aspects that are combined in single ICARS subscores. It is concluded that the combination of clinical assessments and instrumental evaluations allows a better insight into ataxic patients' motor disturbances and is a useful tool for the definition and follow-up of rehabilitation programmes.
Abstract: To investigate the role of voluntary mechanisms and motor learning in head stability and the impact of longitudinal biofeedback training in head control.
Abstract: Objective The purpose of this study was to test if the F-response can be repressed volitionally. Normally, the F-response is used for clinical diagnostics but it also has an important influence on the design of a neural prosthesis involving functional electrical stimulation (FES) and the use of volitional myoelectric signal (MES) for control. Methods Ten neurologically normal subjects were trained to reduce the level of the F-response from the anterior tibial muscle. The nerve to the anterior tibial (TA) muscle was stimulated with constant intensity and frequency (16.6 pulses per second) and the surface myoelectric signal (MES) from the muscle was digitally processed to estimate the F-level. Training was carried out by giving the subject visual feedback on a computer screen of the F-level during the stimulation with the task of keeping the level as low as possible. Each subject had five sessions consisting of 20 stimulation tests, lasting 30 sec each. The subjects acted as their own control and changes in the F-level during the stimulation tests, sessions, and trials, were analyzed. Results There was a significant (p < 0.001) increase in the F-response level within the test period of constant stimulation, but a significant (p < 0.001) decrease from the first to the last test in the session was found. From the first to the last session of a trial, the change was found not significant. Conclusion The level of the F-response may change locally, but there is no indication that a subject can volitionally learn to repress the response, even when given feedback information about the actual level. Therefore the F-waves in the myoelectric signal from a stimulated muscle has to be accounted for when designing devices using a stimulated muscle response for myoelectric control such as eliminating the F-interval from the recorded signal.
Abstract: This paper reports on a simulation study that concerns the design of a non-linear controller for the standing up and the sitting down of a paraplegic patient by means of functional electrical stimulation. The simulations refer to a specific experimental device developed at the Fondazione Don Gnocchi (Italy). This is a seesaw, with the patient on one side and a weight on the other side. The patient is seated so that its posture can be fully known in real-time by continuously monitoring the knee joint angle. By delivering a suitable electrical stimulation to the quadriceps muscles groups, the patient can be raised and made to sit via smooth movements. Hitherto, the only,feedback control law, which has been implemented in this area, is based on a PID controller and usually provides poor tracking performances. Hence, in this work, a non-linear gain scheduling controller has been designed and tested in a series of simulation experiments. The controller is tuned following a gain scheduling strategy: a set of local linear quadratic controllers is designed using a set of linear tangent models. A global non-linear gain scheduled controller is then obtained via interpolation. The gain- scheduled controller is implemented following an advanced strategy that guarantees that the so-called linearization property holds. Copyright © 2004 John Wiley & Sons, Ltd.
Abstract: Different types of visual cue for subjects with Parkinson's disease (PD) produced an improvement in gait and helped some of them prevent or overcome freezing episodes. The paper describes a portable gait-enabling device (optical stimulating glasses (OSGs) that provides, in the peripheral field of view, different types of continuous optic flow (backward or forward) and intermittent stimuli synchronised with external events. The OSGs are a programmable, stand-alone, augmented reality system that can be interfaced with a PC for program set-up. It consists of a pair of non-corrective glasses, equipped with two matrixes of 70 micro light emitting diodes, one on each side, controlled by a microprocessor. Two foot-switches are used to synchronise optical stimulation with specific gait events. A pilot study was carried out on three PD patients and three controls, with different types of optic flow during walking along a fixed path. The continuous optic flow in the forward direction produced an increase in gait velocity in the PD patients (up to + 11% in average), whereas the controls had small variations. The stimulation synchronised with the swing phase, associated with an attentional strategy, produced a remarkable increase in stride length for all subjects. After prolonged testing, the device has shown good applicability and technical functionality, it is easily wearable and transportable, and it does not interfere with gait.
Abstract: This study falls within the ambit of research on functional electrical stimulation for the design of rehabilitation training for spinal cord injured patients. In this context, a crucial issue is the control of the stimulation parameters in order to optimize the patterns of muscle activation and to increase the duration of the exercises. An adaptive control system (NEURADAPT) based on artificial neural networks (ANNs) was developed to control the knee joint in accordance with desired trajectories by stimulating quadriceps muscles. This strategy includes an inverse neural model of the stimulated limb in the feedforward line and a neural network trained on-line in the feedback loop. NEURADAPT was compared with a linear closed-loop proportional integrative derivative (PID) controller and with a model-based neural controller (NEUROPID). Experiments on two subjects (one healthy and one paraplegic) show the good performance of NEURADAPT, which is able to reduce the time lag introduced by the PID controller. In addition, control systems based on ANN techniques do not require complicated calibration procedures at the beginning of each experimental session. After the initial learning phase, the ANN, thanks to its generalization capacity, is able to cope with a certain range of variability of skeletal muscle properties.
Abstract: In the advanced phase of Parkinson's disease (PD), high frequency electrical stimulation (HFS) of the subthalamic nucleus (STN) can represent a good therapeutic option, whose effects on walking have been recently quantified by kinematic and dynamic gait analysis. The goal of the present study was to compare, in a group of PD patients, the effects of STN stimulation and of L-dopa on trunk kinematics during walking. The additive effect of these two treatments was investigated as well. Ten idiopathic PD patients implanted bilaterally with a STN stimulation system and ten age-matched controls were studied using a three dimensional motion analyser. Four conditions were considered: with (s+) and without (s-) STN stimulation and with (m+) and without (m-) L-dopa administration. The results showed that both stimulation alone and L-dopa alone significantly increased the stride length and the gait speed, with an additional effect if applied simultaneously. Cadence was more influenced by L-dopa. The range of lateral bending and torsion of the trunk, which were reduced in s-/m-, increased similarly in s-/m+ and in s+/m- conditions. The exaggerated forward inclination of the trunk reduced towards control values in all therapeutic conditions. There was a tendency for L-dopa to increase trunk movements in the frontal plane, similar to events seen in quiet stance. Due to the presence of additive and synergistic effects, we concluded that the mechanisms of action of the two treatments are likely to be different.
Abstract: An innovative optimised method, including an experiment and a mathematical model, for the calibration of the force platform location in the optoelectronic reference frame is proposed. The calibration experiment adopts a bearing-marker testing object contacting the platform and does not directly measure the platform location. The experiment is designed in order to avoid the main drawbacks possibly occurring in commonly adopted methods. The mathematical model of the experiment estimates the expected ground reaction. An optimisation algorithm identifies the optimal platform location as the one that best matches the measured outcome of the calibration experiment with the corresponding model estimate. The innovative calibration procedure has been assessed in terms of inter-tester reliability and compared with commonly used calibration procedures of platform location. These results evidenced how the introduction of such optimised procedure could improve the reliability of the calibrated platform location and, consequently, of the kinetic variables considered in posture and gait analysis.
Abstract: A new computerised test adopting touch-screen technology has been developed to assess the visuo-motor exploration of extra-personal space. The test was derived from well-known paper-and-pencil cancellation tasks used widely in the diagnosis and quantitative assessment of unilateral spatial neglect (USN), a neuropsychological syndrome that is more frequent and severe after damage to the right cerebral hemisphere. A main component deficit of USN is the defective visuo-motor exploration of the side of space contralateral to the side of the lesion (contralesional), namely, in right-sided brain-damaged patients it occurs on the left side and vice versa. The computer-based paradigm consisted of a visuo-motor spatial exploratory task: the subjects were instructed to touch, in any order they wished, all the targets they detected on a computer touch-screen. This measured the time of occurrence and the spatial co-ordinates of each touch event and forwarded the data to the computer for storage; the computer provided feedback to the subject by 'tagging' the touched target. The paradigm allowed the calculation of accuracy and latency indexes and recorded the exploratory pathway taken by each subject. A pilot study was performed in ten normal subjects and 15 brain-damaged patients, with and without psychometric evidence of USN; the results showed that the equipment was able to provide quantitative indexes related to the spatial-temporal aspects of exploratory ability, which are useful for diagnostic purposes, and revealed significant differences between the controls and patients with USN: the overall average values of latency and crossing indexes increased in patients with USN, compared with the controls (latency from 0.77 to 1.90s; path crossing index from 7.0% to 59.5%), and the significantly negative USN patient latency gradient (-2.79 against a null control value) evidenced a worsening of performance towards the left side.
Abstract: In the advanced phase of Parkinson's disease (PD), gait disturbances represent one of the main causes of disability. Several studies demonstrated that high-frequency electrical stimulation (HFS) of the subthalamic nucleus (STN) significantly improves the motor symptoms of PD. This study was finalised to quantitatively analyze the effect of STN HFS on gait of PD patients, through a three-dimensional gait analysis system. Ten PD patients were studied, with and without STN HFS. The results demonstrated that STN HFS significantly improves all the main gait parameters in PD patients.
Abstract: The on-orbit application of movement analysis methodology, on-board space stations, for studying the gravity role in motor functions, requires a careful adaptation of the currently adopted techniques in order to obtain reliable data. In those operative conditions, differently from common on-ground experimental activities, a non-specialist operator, an astronaut of the space station crew, is expected to self-administer the experimental protocol, particularly self-marking specific anatomical landmarks. The present paper proposes a movement analysis methodology, which fits the specific constraints of space activity and matches the objective of maximising reliability and minimising on-orbit time, and reports normative data about accuracy and precision of the self-marking of an extended set of anatomical landmarks. The same set of landmarks has been considered also for direct-marking performed by experts in motion analysis and their results have been compared to self-marking ones. The paper contents will support the design of future space experimental campaigns and is, in general, applicable to any on-ground scientific investigation, possibly increasing data reliability.
Abstract: Four patients with Parkinson's disease who had a Subthalamic Nucleus (STN) stimulator implanted and four age-matched controls underwent gait analysis using a three-dimensional system. STN stimulation substantially improved most of the key variables in the patients, without producing inefficient compensatory movements of the trunk. A reduction of ankle power production during push off was the most persistent abnormality seen when the patients were stimulated. We also found a reduction of trunk lateral bending and torsion when the patients were not stimulated when compared with controls.
Abstract: The goal of the present work was to develop and test an innovative system for the training of paraplegic patients when they are standing up. The system consisted of a computer-controlled stimulator, surface electrodes for quadricep muscle stimulation, two knee angle sensors, a digital proportional-integrative-derivative (PID) controller and a mechanical device to support, partially, the body weight (weight reliever (WR)). A biomechanical model of the combined WR and patient was developed to find an optimum reference trajectory for the PID controller. The system was tested on three paraplegic patients and was shown to be reliable and safe. One patient completed a 30-session training period. Initially he was able to stand up only with 62% body weight relief, whereas, after the training period, he performed a series of 30 standing-up/sitting-down cycles with 45% body weight relief. The closed-loop controller was able to keep the patient standing upright with minimum stimulation current, to compensate automatically for muscle fatigue and to smooth the sitting-down movement. The limitations of the controller in connection with a highly non-linear system are considered.
Abstract: The objective of this study was to test myoelectrically controlled functional electrical stimulation of the some muscle (AutoMCS) on patients with either stroke or spinal cord injury. The paretic anterior tibialis (TA) muscle was stimulated with an amplitude controlled continuously by the volitional myoelectric signal from the same muscle. Surface electrodes were used and volitional myoelectric signals were extracted by analog/digital signal processing techniques. Isometric dorsiflexion torque of the foot was displayed on a screen and the subjects were asked to track a sinusoidal curve, Subjects with dropped foot, as a result of a stroke (CVA, n = 9) or spinal cord lesion (SCI, n = 4), performed tests without and then with AutoMCS applied to the muscle. Subjects were their own control and tracking tests without and with AutoMCS. Changes in torque range, tracking delay, and tracking control accuracy have been evaluated. A significant (p < 0.05) increase of dorsiflexion torque by AutoMCS was found. An immediate carryover effect was seen in one stroke subject. The analysis of the tracking control showed only little loss of controllability with the system. We conclude that for selected subjects this method can instantly increase the muscle force of the anterior tibialis without significantly compromising tracking control or tracking delay.
Abstract: Previous studies have shown that far space can be remapped as near when reached by a stick that artificially prolongs the participants' personal space. In the present study, the authors asked whether a similar remapping occurs when far space is reached not by using a tool but by locomotion. Neglect patients showed more severe neglect in far than in near space in bisection tasks executed from different distances either by pointing to a target line with a projection light pen or by walking across the line. A kinematic study of the walking performance of one of those neglect patients showed that, contrary to the prediction of remapping during locomotion, the walking trajectories were rectilinear. The authors interpreted these results as evidence that in their patients-at least for short, linear trajectories-no remapping of space took place during locomotion. The location of far objects was coded at the beginning of the movement, and the error in the bisection computation was generated within the 1st representation that was activated.
Abstract: In a movement analysis laboratory, stereophotogrammetric motion capture systems and force platforms must share one absolute reference frame that allows the computation of joint moments and powers. The correct calibration of the platform location identifies the transformation between force plate and absolute reference systems, which determines the spatial coherence among the equipments' measurements. The aim of this study was to develop and test a spot check for the assessment of platform location calibration. Platform location calibration was assessed by comparing the measured outcome of an experiment performed with a pointed rigid rod bearing a set of markers with the corresponding expected results, computed with a model. A set of indices was then proposed to define a confidence volume in which the true ground reaction force is expected to be. The spot check was applied to a real laboratory setup and the effects of simulated platform mislocations were analysed. It was verified that the hip joint moment may be equally affected by a single marker misplacement of about 20mm during platform location calibration, an occurrence that was clearly identified by the spot check, and by a hip centre location inaccuracy of 30mm.
Abstract: Functional electrical stimulation (FES) of upper limbs can be used for the recovery of some hand functions on patients with CNS lesions. This study deals with the control of FES by means of myoelectrical activity detected from voluntarily activated paretic muscles. The specific aim of this paper is to evaluate the accuracy of myoelectrical control in terms of produced force and movement. For this purpose, a specific device called myoelectrical controlled functional electrical stimulator (MeCFES) has been developed and applied to six tetraplegic patients with a spinal cord lesion and one stroke hemiplegic patient. Residual myoelectric signals from the paretic wrist extensor (m. extensor carpi radialis, ECR) have been used to control stimulation of either the wrist extension (i.e., the same muscle) or thumb flexion. A tracking test based on a visual feedback of the produced force or movement compared to a reference target trajectory was used to quantify control accuracy. A comparison was made between the tracking performances of each subject with and without the MeCFES and the learning process for two of the subjects were observed during consecutive sessions. Results showed that the wrist extension was improved in three out of five C5 SCI patients and the thumb flexion was largely increased in one incomplete C3 SCI patient. The hemiplegic patient showed limited thumb control with the MeCFES but indicated the possibility of a carry over effect. It was found that a low residual natural force resulted in a less accurate movement but also with a large increase (up to ten times) of the muscle output. On the contrary, persons with a medium residual force obtained a smaller amplification of muscle force with a higher tracking accuracy.
Abstract: A crucial issue of functional electrical stimulation (FES) is the control of motor function by the artificial activation of paralyzed muscles. Major problems that limit the success of current FES systems are the nonlinearity of the target system and the rapid change of muscle properties due to fatigue. In this study, four different strategies, including an adaptive algorithm, to control the movement of the freely swinging shank were developed on the basis of computer simulations and experimentally evaluated on two subjects with paraplegia due to a complete thoracic spinal cord injury. After developing a nonlinear, physiologically based model describing the dynamic behavior of the knee joint and muscles, an open-loop approach, a closed-loop approach, and a combination of both were tested. In order to automate the individual adjustments cited above, we further evaluated the performances of an adaptive feedforward controller. The two parameters chosen for the adaptation were the threshold pulse width and the scaling factor for adjusting the active moment produced by the stimulated muscle to the fitness of the muscle. These parameters have been chosen because of their significant time variability. The first three controllers with fixed parameters yielded satisfactory result. An additional improvement was achieved by applying the adaptive algorithm that could cope with problems due to muscle fatigue, thus permitting on-line identification of critical parameters of the plant. Although the present study is limited to a simplified experimental setup, its applicability to more complex and functional movements can be expected.
Abstract: A patient-driven control strategy for standing-up and sitting-down was experimentally tested on two paraplegic patients by applying functional electrical stimulation (FES) to the quadriceps muscle. The strategy--also known as "patient-driven motion reinforcement" (PDMR)--was developed by computer simulations reported in a former study. It is based on an inverse dynamic model (IDM) that predicts the stimulation pattern required to maintain the movement as it is initiated by the patient's voluntary effort. For reasons of safety and weight relief, the movement was supported by a seesaw construction. After some practice the patients were able to influence the stimulator output and to control the movement by their voluntary effort. Consequently, no pre-programmed reference trajectory was required. As a positive side effect, upper body effort could be minimized compared to trials without FES. To achieve a satisfactory performance of the PDMR controller a careful parameter identification of the inverse dynamic model was fundamental.
Abstract: The surface EMG signal detected from voluntarily activated muscles can be used as a control signal for functional neuromuscular electrical stimulation. A proper positioning of the recording electrodes in relation to the stimulation electrodes, and a proper processing of the recorded signals is required to reduce the stimulus artefact and the non-voluntary contribution (M-wave). Six orientations and six locations of the recording electrodes were investigated in the present work. A comb filter (with and without a blanking windowing) was applied to remove the signal components synchronously correlated to the stimulus. An operative definition of the signal to noise ratio and an efficiency index were implemented. It resulted that when the recording electrodes were located within the two stimulation electrodes the best orientation was perpendicular to the longitudinal line. However the best absolute indexes were obtained when the recording electrodes were located externally of the stimulation electrodes, and in that case the best orientation was longitudinal. Concerning the filtering procedure, the use of a blanking window before the application of the comb filter, gave the best performance.
Abstract: The knowledge of the behavior of electrically activated muscles is an important requisite for the development of functional electrical stimulation (FES) systems to restore mobility to persons with paralysis. The aim of this work was to develop a model capable of relating electrical parameters to dynamic joint torque for FES applications. The knee extensor muscles, stimulated using surface electrodes, were used for the experimental preparation. Both healthy subjects and people with paraplegia were tested. The dynamics of the lower limb were represented by a nonlinear second order model, which took account of the gravitational and inertial characteristics of the anatomical segments as well as the damping and stiffness properties of the knee joint. The viscous-elastic parameters of the system were identified experimentally through free pendular movements of the leg. Leg movements induced by quadriceps stimulation were acquired too, using a motion analysis system. Results showed that, for the considered experimental conditions, a simple one-pole transfer function is able to model the relationship between stimulus pulsewidth (PW) and active muscle torque. The time constant of the pole was found to depend on the stimulus pattern (ramp or step) while gain was directly dependent on stimulation frequency.
Abstract: To study the energy cost of locomotion during ambulation with different orthoses (HIP Guidance Orthosis Orlau Parawalker (PW), n=4; Reciprocating Gait Orthosis (RGO), n=6; RGO + FNS, n=4).
Abstract: Thermal properties of wheelchair cushions have been traditionally studied with thermistor probes, which provide temperature values of limited areas (spot analysis). In this paper, we describe a novel procedure based on thermography for assessing the distribution of temperature over the entire surface of wheelchair cushions. The thermal transient during contact with the body (heating phase) and after use (cooling phase) is considered. The procedure was tested in four different seat cushions (with a gel pad, air-filled cells, gel-filled bubbles and foam-filled bubbles) used by a normal subject. Observed results were compatible with the predicted outcomes based on an analysis of the materials and structures. Specifically: (i) air-filled cushions exhibited the fastest thermal transients, gel cushions the slowest transients, while cushions with a mixed structure exhibited intermediate behaviour; (ii) cushions made from flat surfaces of foam exhibited the highest peak temperatures (30.8 degrees C) as compared to those with air-filled cells (30.35 degrees C) or bubble-shaped surfaces (29.7 degrees C); (iii) the average temperature under the thighs was significantly higher than that under the ischiatic area in all cushions (29.6 degrees C compared with 28.7 degrees C, p < 0.05). It is shown that the present method can be used to differentiate between different cushions. Although the 'macro-analysis' inherent in thermography appears to be suited for improving cushion design, this approach should be further investigated to determine its reliability.
Abstract: The aim of the present study was to perform a comparative biomechanical analysis of four antidecubitus wheelchair cushions. Thirty wheelchair users were considered divided into three groups: paraplegic subjects (with no cutaneous sensation), neurologic subjects (with intact cutaneous sensation), and elderly subjects. The biomechanical evaluation was performed using a piezoresistive sensor matrix system to quantify parameters referred to pressure distribution, seating surface and posture. Dedicated software was developed for the automatic elaboration of the raw data and the computation of the parameters of interest. Differences among cushion types and subject groups were analyzed. An analysis of time-transient behaviors was also performed. Results showed that no significant differences in pressure peak reduction were found among the four cushions. Moreover, no time-transient behavior was shown by any cushions. However, both the location of pressure peaks and posture were dependent on cushion types. Comparison of the three subject groups showed that elderly subjects had the highest mean pressure and the lowest contact surface, while paraplegics presented the highest pressure peaks. This procedure appears indicated for individualizing the prescription of a wheelchair cushion and even for customizing a cushion to induce a specific posture.
Abstract: A microprocessor controlled device (MeCFES) was used for the investigation of the possibility of restoring hand function in C5 tetraplegics with paralysis of the hand. To date, 3 tetraplegics have been testing the system. The myoelectric signals from wrist extension were recorded and used as control signals for functional electrical stimulation (FES) of thumb adduction/flexion. The results have shown that the device can improve the hand function of tetraplegics. In this part of the work, a hand function test was designed and used to assess the results.
Abstract: Although good results have already been achieved in reciprocal walking for paraplegic patients using mechanical orthoses (e.g. ORLAU ParaWalker), improvements in lateral stiffness of walking devices could increase significantly the efficiency of ambulation. For this reason a method for monitoring the structural properties of an orthosis during locomotion has been studied. A motion analysis system (ELITE system) able to detect automatically and accurately the positions of small retroreflective markers in a television field was used. Starting from marker positions, the angular variations between adjacent structural segments in the orthosis were computed and the areas in which maximum deformations occurred were identified. Experiments were performed on two paraplegic patients using their ORLAU ParaWalker orthosis and two different kinds of movements were analysed: lateral tilting and walking. The results show that this approach is able to detect the small deformations occurring in the orthotic structure and therefore to provide valuable information for orthotic design optimization.
