Authors:
Guilherme N. Nogueira-Neto
1
;
Eddy Krueger
2
;
Eduardo M. Scheeren
3
;
Vera L. S. N. Button
4
and
Percy Nohama
5
Affiliations:
1
Pontifícia Universidade Católica do Paraná and Universidade Estadual de Campinas, Brazil
;
2
Universidade Tecnológica Federal do Paraná, Brazil
;
3
Pontifícia Universidade Católica do Paraná, Brazil
;
4
Universidade Estadual de Campinas, Brazil
;
5
Pontifícia Universidade Católica do Paraná, Universidade Tecnológica Federal do Paraná and Universidade Estadual de Campinas, Brazil
Keyword(s):
Convex Hull, Triaxial Mechanomyography, Functional Electrical Stimulation.
Related
Ontology
Subjects/Areas/Topics:
Applications and Services
;
Biomedical Engineering
;
Biomedical Signal Processing
;
Computer Vision, Visualization and Computer Graphics
;
Informatics in Control, Automation and Robotics
;
Medical Image Detection, Acquisition, Analysis and Processing
;
Signal Processing, Sensors, Systems Modeling and Control
;
Time and Frequency Response
;
Time-Frequency Analysis
Abstract:
This study employed the convex hull in the analysis of triaxial mechanomyography (MMG) to determine hull area variations along prolonged muscle contractions elicited by functional electrical stimulation (FES). Closed-loop FES systems may need real-time adjustments in control parameters. Such systems may need to process small sample sets. The convex hull area can be applied to small sample sets and it does not suffer with non-stationarities. The MMG sensor used a triaxial accelerometer and the acquired samples were projected onto all planes. The hull determined the smallest convex polygon surrounding all points and its area was computed. Four spinal cord injured volunteers participated in the experiment. The quadriceps femoral muscle was stimulated in order to cause a full knee extension. FES parameters: 1 kHz pulse frequency and a 20 Hz burst frequency. Adjustments in the stimuli amplitude were controlled by a technician to sustain the extension. The results showed that the convex hu
ll area decreased over time. Since the polygons are related to MMG amplitude, decreasing areas were related to muscle fatigue. The convex hull area can be a candidate to follow muscle fatigue during FES-elicited contractions and analysis of short length epochs.
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