STUDY Of Electromyographic Patterns Of erector Spinae And Lower-limb Muscles during Different Modalities Of Gait In post-stroke Individuals

Stroke is one of the leading causes of motor disability in the world. New technologies have been developed to increase efficiency and reduce costs of rehabilitation of poststroke individuals. Objective: To compare electromyographic patterns related to muscle onset/offset, duration of activation and analysis of neuromuscular fatigue of erector spinae (ES) and lower-limb muscles during different modalities of gait in poststroke and healthy individuals. Methodology: The changes in the median frequency (MDF) was analyzed during isometric tasks and walking on a treadmill in healthy individuals (N = 10) to identify fatigue. Ten post-stroke and 30 healthy subjects participated of the second stage of the study, in which ES and three lower-limb muscles were analyzed during different gaits (walking on treadmill and ground, with and without arm swing, and using a walker), with the neuromuscular fatigue analyzed in stroke gait. Muscle analysis was also conducted with two post-stroke subjects while using the UFESs robotic walker. Results: For the healthy subjects, all the lower-limb muscles showed reduction in their MDF during walking on treadmill. Walking on treadmill had a stronger influence on the onset/offset muscles than the arm swing in the healthy individuals. For post-stroke subjects, their ES muscles presented a similar pattern to the healthy subjects, but the contralateral side had longer activation near the toe-off than the ipsilateral side in both gaits. All the observed changes in the activation for each phase indicated a longer duration of activation of the post-stroke subjects. Regarding neuromuscular fatigue, it was not possible to detect reduced MDF values for post-stroke individuals. The use of the UFESs robotic walker improved the symmetry of one post-stroke subject, and the symmetry of duration of activation in the swing phase for all muscles of the other subject. Conclusion: MDF changes were detected in non-strenuous exercises in healthy subjects. ES muscle activation is not influenced by arm swing in healthy individuals, with the same behavior in post-stroke individuals. As a finding of this research, we concluded that trunk muscles can be used in rehabilitation processes and also to control robotic devices for assistance or rehabilitation

State observability and observers of linear-time-invariant systems under irregular sampling and sensor limittations

Abstract-State observability and observer designs are investigated for linear-time-invariant systems in continuous time when the outputs are measured only at a set of irregular sampling time sequences. The problem is primarily motivated by systems with limited sensor information in which sensor switching generates irregular sampling sequences. State observability may be lost and the traditional observers may fail in general, even if the system has a full-rank observability matrix. It demonstrates that if the original system is observable, the irregularly sampled system will be observable if the sampling density is higher than some critical frequency, independent of the actual time sequences. This result extends Shannon's sampling theorem for signal reconstruction under periodic sampling to system observability under arbitrary sampling sequences. State observers and recursive algorithms are developed whose convergence properties are derived under potentially dependent measurement noises. Persistent excitation conditions are validated by designing sampling time sequences. By generating suitable switching time sequences, the designed state observers are shown to be convergent in mean square, with probability one, and with exponential convergence rates. Schemes for generating desired sampling sequences are summarized