Gaussian mixture model based clustering of Manual muscle testing grades using surface Electromyogram signals
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SCIENTIFIC PAPER
Gaussian mixture model based clustering of Manual muscle testing grades using surface Electromyogram signals S. Saranya1 · S. Poonguzhali1 · S. Karunakaran2 Received: 7 August 2019 / Accepted: 10 May 2020 © Australasian College of Physical Scientists and Engineers in Medicine 2020
Abstract Muscle strength testing has long been an important assessment procedure in rehabilitation setups, though the subjectivity and standardization of this procedure has been widely debated. To address this issue, this study involves the use of Electromyogram (EMG) features that are intuitively related to muscle strength to classify Manual muscle testing (MMT) grades of ‘4 −’, ‘4’, ‘4 + ’ and ‘5’ of the Medical Research Council scale. MMT was performed on Tibialis anterior muscle of 50 healthy participants whose MMT grades and EMG were simultaneously acquired. Chi square goodness of fit and Spectrum Decomposition of Graph Laplacian (SPEC) feature selection algorithms are used in selecting five features, namely Integrated EMG, Root Mean Square EMG, Waveform Length, Wilsons’ amplitude and Energy. Gaussian Mixture Model (GMM) approach is used for unsupervised clustering into one of the grades. Internal cluster evaluation resulted in Silhouette score of 0.76 and Davies Bouldin Index of 0.42 indicating good cluster separability. Agreement between the machine-based grade and manual grade has been quantified using Cohens’ Kappa coefficient. A value of ‘0.44’ has revealed a moderate agreement, with greater differences reported in grading ‘4’ and ‘4 + ’ strength levels. The comparative advantage of EMG based grading over the manual method has been proved. The suggested method can be extended for muscle strength testing of all muscles across different age groups to assist physicians in evaluating patient strength and plan appropriate strength conditioning exercises as a part of rehabilitative assessment. Keywords Muscle strength · Electromyogram · Gaussian mixture model · Clustering · MMT grades
Introduction The overall quality of life is measured based on the ability to carry out daily activities that greatly relies on mobility of an individual. Muscle function is crucial in this aspect and it is affected by factors like age and other medical conditions where the lower limb muscles become weak and inefficient to support movement. Among the several lower limb muscles involved in movement, Tibialis Anterior (TA) is the strongest dorsiflexor and inverter of the foot at the ankle joint. It is the major muscle that offers ground clearance of foot during the swing phase of gait. Injury to TA can be chronic as in the case of tibial paralysis leading to foot drop
* S. Saranya [email protected] 1
Department of ECE, Anna University, Chennai, India
Institute of Advanced Spine Sciences, Gleaneagles Global Health City, Chennai, India
2
or due to acute/repetitive loading as in anterior tibial tendinitis, a condition often presented in athletes [1]. In both cases following a surgical repair, strengthening exerc
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