Stanko Tonković

Measurement and analysis of surface myoelectric signals during fatigued cyclic dynamic contractions

Abstract A method of surface myoelectric (ME) signal measurement and analysis, with the aim of evaluating muscle fatigue during cyclic dynamic contractions of quadriceps muscle (lower leg extension and flexion exercise on ‘leg-extension’ training device), was developed. As an indicator of muscle fatigue a change in the power spectrum median frequency (MF), calculated from the spectrogram, has been used. Our method considers the maximum median frequency values during each contraction. A slope of the regression line (Hz/min) that fits the maximum values of MF in a least-square sense was used as a fatigue index. Dependencies of the muscle fatigue index, as well as median frequencies at the beginning of the exercise on spectrogram analysis parameters were considered, and analysis parameters for reliable results were chosen. Values of the slope of the regression line and MF at the beginning of an exercise are in agreement with the notion that rectus femoris has higher muscle fibre conduction velocity than both vasti muscles.

Effects of Transmitter Position and Receiver Ground Plane on Signal Transmission in Intrabody Wireless EMG Measurement System

We investigate relation between the received signal strength and relative positions of the receiver and transmitter in an intrabody communication (IBC) system previously designed for electromyography (EMG) measurements in kinesiology, sports medicine and rehabilitation. The receiver signal electrode was placed on the subject’s left wrist and the transmitter was moved along the arms. We analyze effects of the receiver ground plane size and provide its upper limit beyond which further increase in the received signal strength is insignificant.

The choice of camera setup in 3D motion reconstruction systems

In this study the accuracy of 3D reconstruction systems using different camera setup in horizontal or vertical direction (plane) was investigated. Since it is critical that the object being filmed has to be visible by at least two cameras one is trying to keep cameras as parallel as possible to increase a common field of view. Also a camera positioned perpendicular to the area of interest assures better resolution in the horizontal and vertical directions (X-axis and Y-axis). On the other hand the depth resolution (Z-axis) suffers when cameras optical axes do not converge enough. Theoretically and also shown in practice angle of intersection from 60/spl deg/ to 120/spl deg/ is equally reliable. The convergent vertical camera set-up (one camera positioned above the other) is expected to encompass both requirements: depth of resolution and satisfactory large common field of view.

Method to evaluate the skill level in fast locomotion through myoelectric and kinetic signal analysis

The paper describes a method aimed at providing objective diagnostic testing of skilled locomotor stereotypes. Bioelectric muscle activity indices and ground reaction force data are used to represent a movement structure, in a schematised way, using discrete states in time. Athletes were asked to perform one specific movement structure: a backward somersault from the standing position. Mathematical analyses of measured signals reveal the significance, for the skill level evaluation, of parameters reflecting the impulsive take-off force waveform and the symmetry in EMG activity of ankle extensor muscles, which therefore might be used as diagnostic criteria. Within technical limitations, this approach may also be applied to other locomotor patterns and possibly to monitor the progress in motorics in pathological locomotion. EMG telemetry could significantly enhance the methods scope.

Human Gait Data Mining by Symbol Based Descriptive Features

Most medical applications which include large dataset require search by example capability. Such similarity- based retrieval has attracted a great deal of attention in recent years. Although several different approaches have appeared, most are not specialized for problems of time series signals, typically found in gait analysis or ECG. This paper proposes an approach for efficient processing of human gait by using symbolization of different features by means of feature description. We evaluated this approach against database that holds limited set of kinematics, kinetic and EMG data, describing simple step (a subset of standard gait variables). The measurement was performed in the Biomechanics Laboratory at the Faculty of Kinesiology, University of Zagreb, using 2002-ELITE system with Kistler platform (40 cm by 60 cm).

Towards a High Performance Expert System for Gait Analysis

In a number of decision support systems searching through large data warehouse based on sample sequence is desirable. Gait analysis systems store demographic data (categorical, numerical data) and time sequence data (human gait variables) where query by example is needed for matching signal patterns. Although several different approaches have appeared, most of them are not specialized for the problem which combines simple facts and time series data or data warehousing principles for such data. We propose an end-to-end approach including data warehouse partitioning, symbolic-based algorithms, clustering-based algorithms for purpose of fast and intelligent retrieval and classification of stored facts. This paper gives the modified version of symbolic algorithm that allows dimensionality reduction and indexing with a lower-bounding distance measure. Paper shows how it can be used together with clustering based algorithms for efficient processing of time-series data stored in large fact tables of a data warehouse. Each symbolic word serves as input to hierarchical clustering algorithm and forms a node in the dendrogram representation (graph which displays nodes arranged into hierarchy). In a data warehouse this design improves performance in addition to denormalization, by adding derived information and summary tables. Input signal is divided into segments to reduce the length of the symbolic words. Since each word is represented as a simple fact in a database, hierarchical clustering algorithms can be applied. We have tested this approach on human locomotion data combining categorical, numerical and time series variables. Input dataset included ground reaction force during a simple step, representing a subset of standard gait variables, demographic and anthropometric parameters. The measurements were performed in the Biomechanics Laboratory at the Faculty of Kinesiology, University of Zagreb, using 2002-ELITE system with Kistler platform (40 cm by 60 cm).

Data mining time series of human locomotion data based on functional approximation

In many of medical applications specially one considering time sequence data like data describing human gait, searching through large, unstructured databases based on sample sequences is often desirable. Such similarity-based retrieval has attracted a great deal of attention in recent years. Although several different approaches have appeared, most are not specialized for the problem of human locomotion. This paper gives an overview of one proposed approach how to efficiency process human gait by using Fourier’s series approximation, genetic algorithms for coefficients corrections and Spectral Signatures as data mining method. This paper shows how these methods fit into a general context of signature extraction and disorder recognition in the human gait case.

A DSP based method for audio stimuli generation

Audio stimuli generation for tonal audiometry, realized by direct digital synthesis (DDS) is described. Introduction of digital methods in audiometry enables not only increased parameter accuracy and resolution, but simple research with new examination procedures. The signal obtained by the developed generator based on a digital signal processor (ADSP 2181) showed excellent properties for application in tonal audiometry: high spectral purity, high signal/noise ratio, high frequency and amplitude resolution and accuracy.

Development of the quality assessment model of EHR software in family medicine practices: research based on user satisfaction.

Background Family medicine practices (FMPs) make the basis for the Croatian health care system. Use of electronic health record (EHR) software is mandatory and it plays an important role in running these practices, but important functional features still remain uneven and largely left to the will of the software developers. Objective The objective of this study was to develop a novel and comprehensive model for functional evaluation of the EHR software in FMPs, based on current world standards, models and projects, as well as on actual user satisfaction and requirements. Methods Based on previous theoretical and experimental research in this area, we made the initial framework model consisting of six basic categories as a base for online survey questionnaire. Family doctors assessed perceived software quality by using a five-point Likert-type scale. Using exploratory factor analysis and appropriate statistical methods over the collected data, the final optimal structure of the novel model was formed. Special attention was focused on the validity and quality of the novel model. Results The online survey collected a total of 384 cases. The obtained results indicate both the quality of the assessed software and the quality in use of the novel model. The intense ergonomic orientation of the novel measurement model was particularly emphasised. Conclusions The resulting novel model is multiple validated, comprehensive and universal. It could be used to assess the user-perceived quality of almost all forms of the ambulatory EHR software and therefore useful to all stakeholders in this area of the health care informatisation.

Quality assessment model of software for managing family medicine practice — Methodology and basic results

Family medicine practices form the basis of the Croatian health system. They solve the largest number of health problems and collect the most health data with the lowest operational cost. However, the software support required for the running of these offices at the time being is still certified only based on the principal communication criteria, while all other essential functionalities are generally uneven and left to the will of the producers. It is necessary to assess the quality of this type of software. Based on previous theoretical and experimental research in this area, the initial quality assessment model consisting of six basic categories and the questionnaire by which the Croatian family physicians evaluated the quality of the functionalities applied in their software support were made. The resulting novel model is multiple validated, comprehensive and universal. The intense ergonomic orientation of the novel measurement model was particularly emphasized.