2012 4th IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics (BioRob), 2012
In this paper we discuss two possible strategies of movement control that can be used by stroke s... more In this paper we discuss two possible strategies of movement control that can be used by stroke survivors during rehabilitation robotics training. To perform a reaching task in a minimally assistive force field, subjects either can move following the trajectory provided by the assistive force or they can use an internal representation of a minimum jerk trajectory from their starting position to the target. We used the stiffness and damping values directly estimated from the experimental data to simulate the trajectories that result by taking into account both hypotheses. The comparison of the simulated results with the data collected on four hemiparetic subjects supports the hypothesis that the central nervous system (CNS) is still able to correctly plan the movement, although a normal execution is impaired.
IEEE ... International Conference on Rehabilitation Robotics : [proceedings], 2011
Impaired arm movements in stroke appear as a set of stereotypical kinematic patterns, characteriz... more Impaired arm movements in stroke appear as a set of stereotypical kinematic patterns, characterized by abnormal joint coupling, which have a direct consequence on arm mechanics and can be quantified by the net arm stiffness at the hand. The current available measures of arm stiffness during functional tasks have limited clinical use, since they require several repetitions of the same test movement in many directions. Such procedure is difficult to obtain in stroke survivors who have lower fatigue threshold and increased variability compared to unimpaired individuals. The present study proposes a novel, fast quantitative measure of arm stiffness during movements by means of a Time-Frequency technique and the use of a reassigned spectrogram, applied on a trial-by-trial basis with a single perturbation. We tested the technique feasibility during robot mediated therapy, where a robot helped stroke survivors to regain arm mobility by providing assistive forces during a hitting task to 13...
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2000
Abstract-Spasticity and muscular hypertonus are frequently found in stroke survivors and may have... more Abstract-Spasticity and muscular hypertonus are frequently found in stroke survivors and may have a significant effect on functional impairment. These abnormal neuro-muscular properties, which are quantifiable by the net impedance of the hand, have a direct consequence on arm mechanics and are likely to produce anomalous motor paths. Literature studies quantifying limb impedance in stroke survivors have focused on multijoint static tasks and single joint movements. Despite this research, little is known about the role of sensory motor integration in post-stroke impedance modulation. The present study elucidates this role by integrating an evaluation of arm impedance into a robotically mediated therapy protocol. Our analysis had three specific objectives: 1) obtaining a reliable measure for the mechanical proprieties of the upper limb during robotic therapy; 2) investigating the effects of robot assisted training and visual feedback on arm stiffness and viscosity; 3) determining if the stiffness measure and its relationship with either training or visual feedback depend on arm position, speed, and level of assistance. This work demonstrates that the performance improvements produced by minimally assistive robot training are associated with decreased viscosity and stiffness in stroke survivors' paretic arm and that these mechanical impedance components are partially modulated by visual feedback.
We tested an innovative method to estimate joint stiffness and damping during multi-joint 27 unfe... more We tested an innovative method to estimate joint stiffness and damping during multi-joint 27 unfettered arm movements. The technique employs impulsive perturbations and a time-28 frequency analysis to estimate the arm's mechanical properties along a reaching trajectory. Each 29 single impulsive perturbation provides a continuous estimation on a single reach basis, making 30 our method ideal to investigate motor adaptation in the presence of force fields and to study the 31 control of movement in impaired individuals with limited kinematic repeatability. In contrast 32 with previous dynamic stiffness studies, we found that stiffness varies during movement 33 achieving levels higher than postural. High stiffness was associated with elevated reflexive 34 activity. We observed that a marked reduction in long latency reflexes about and after the 35 reaching movement velocity peak coincides with a decrease in stiffness. This could partly 36 explain the difference between the high stiffness reported by postural studies and the low 37 stiffness measured in dynamic estimation studies where perturbations were applied in proximity 38 to the peak velocity point. 39 40
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2011
Stroke survivors strongly rely on visual feedback to control their movements, since segmental ref... more Stroke survivors strongly rely on visual feedback to control their movements, since segmental reflexes are characterized by an inherent hyper-excitability. To test the effect of visual feedback on the modulation of arm stability we estimated the stiffness of the paretic arm in nine stroke survivors during robot mediated therapy, where subjects trained with and without vision. While several studies found a negligible effect in unimpaired individuals, our results highlighted a marked reduction of stroke survivors' arm stiffness in absence of visual feedback.
2012 4th IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics (BioRob), 2012
In this paper we discuss two possible strategies of movement control that can be used by stroke s... more In this paper we discuss two possible strategies of movement control that can be used by stroke survivors during rehabilitation robotics training. To perform a reaching task in a minimally assistive force field, subjects either can move following the trajectory provided by the assistive force or they can use an internal representation of a minimum jerk trajectory from their starting position to the target. We used the stiffness and damping values directly estimated from the experimental data to simulate the trajectories that result by taking into account both hypotheses. The comparison of the simulated results with the data collected on four hemiparetic subjects supports the hypothesis that the central nervous system (CNS) is still able to correctly plan the movement, although a normal execution is impaired.
IEEE ... International Conference on Rehabilitation Robotics : [proceedings], 2011
Impaired arm movements in stroke appear as a set of stereotypical kinematic patterns, characteriz... more Impaired arm movements in stroke appear as a set of stereotypical kinematic patterns, characterized by abnormal joint coupling, which have a direct consequence on arm mechanics and can be quantified by the net arm stiffness at the hand. The current available measures of arm stiffness during functional tasks have limited clinical use, since they require several repetitions of the same test movement in many directions. Such procedure is difficult to obtain in stroke survivors who have lower fatigue threshold and increased variability compared to unimpaired individuals. The present study proposes a novel, fast quantitative measure of arm stiffness during movements by means of a Time-Frequency technique and the use of a reassigned spectrogram, applied on a trial-by-trial basis with a single perturbation. We tested the technique feasibility during robot mediated therapy, where a robot helped stroke survivors to regain arm mobility by providing assistive forces during a hitting task to 13...
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2000
Abstract-Spasticity and muscular hypertonus are frequently found in stroke survivors and may have... more Abstract-Spasticity and muscular hypertonus are frequently found in stroke survivors and may have a significant effect on functional impairment. These abnormal neuro-muscular properties, which are quantifiable by the net impedance of the hand, have a direct consequence on arm mechanics and are likely to produce anomalous motor paths. Literature studies quantifying limb impedance in stroke survivors have focused on multijoint static tasks and single joint movements. Despite this research, little is known about the role of sensory motor integration in post-stroke impedance modulation. The present study elucidates this role by integrating an evaluation of arm impedance into a robotically mediated therapy protocol. Our analysis had three specific objectives: 1) obtaining a reliable measure for the mechanical proprieties of the upper limb during robotic therapy; 2) investigating the effects of robot assisted training and visual feedback on arm stiffness and viscosity; 3) determining if the stiffness measure and its relationship with either training or visual feedback depend on arm position, speed, and level of assistance. This work demonstrates that the performance improvements produced by minimally assistive robot training are associated with decreased viscosity and stiffness in stroke survivors' paretic arm and that these mechanical impedance components are partially modulated by visual feedback.
We tested an innovative method to estimate joint stiffness and damping during multi-joint 27 unfe... more We tested an innovative method to estimate joint stiffness and damping during multi-joint 27 unfettered arm movements. The technique employs impulsive perturbations and a time-28 frequency analysis to estimate the arm's mechanical properties along a reaching trajectory. Each 29 single impulsive perturbation provides a continuous estimation on a single reach basis, making 30 our method ideal to investigate motor adaptation in the presence of force fields and to study the 31 control of movement in impaired individuals with limited kinematic repeatability. In contrast 32 with previous dynamic stiffness studies, we found that stiffness varies during movement 33 achieving levels higher than postural. High stiffness was associated with elevated reflexive 34 activity. We observed that a marked reduction in long latency reflexes about and after the 35 reaching movement velocity peak coincides with a decrease in stiffness. This could partly 36 explain the difference between the high stiffness reported by postural studies and the low 37 stiffness measured in dynamic estimation studies where perturbations were applied in proximity 38 to the peak velocity point. 39 40
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2011
Stroke survivors strongly rely on visual feedback to control their movements, since segmental ref... more Stroke survivors strongly rely on visual feedback to control their movements, since segmental reflexes are characterized by an inherent hyper-excitability. To test the effect of visual feedback on the modulation of arm stability we estimated the stiffness of the paretic arm in nine stroke survivors during robot mediated therapy, where subjects trained with and without vision. While several studies found a negligible effect in unimpaired individuals, our results highlighted a marked reduction of stroke survivors' arm stiffness in absence of visual feedback.
Uploads
Papers by D. Piovesan