Wolfgang Laurig

An Analysis of Heart Rate Variability

Proceeding from a formal definition of heart rate variability, some mathematical and statistical techniques from sampling statistics and time series analysis for the analytical evaluation of heart rate variability for ergonomics purposes are presented and compared. The concept of sampling statistics gives a measure of heart rate variability, arrived at by combining two measures, which were chosen according to a definite criterion. The applicability of this measure is discussed; especially with respect to serial correlation influences when using statistical tests. The two main methods of spectral analysis—the calculation of the transformed autocovariance function and of harmonic analysis–are presented. The influences of interpolations, algorithms and physiological effects are discussed. A possible measure of heart rate variability, calculated by spectral estimates, is proposed and some results are given.

Heart Rate Variability and Work-Load Measurement

Heart rate variability is a result of the superimposition of different sources of variation which are systemized. Three parameters are used to describe the phenomenon of heart rate variation. The range of variation of these parameters is discussed using examples from both laboratory and field investigations. Analyses demonstrate a correlation between heart rate and their variability. Discussion of of the variation of the chosen parameters suggests that, when heart rate variability is used as a measure of strain in field research, strain might be under-assessed.

Ermittlung der Pulsfrequenzarrhythmie bei körperlicher Arbeit

Summary1.Due to the non-normal distribution of the single heart rate values, simple statistic measures of variation are not suitable for description of arrhythmia of heart rate.2.A measure for arrhythmia of heart rate has to consider variations of heart rate either in amplitude and frequency.3.The derived “Quotient of Arrhythmia” (ARQ) decreases with load as well as with heart rate. A stochastic part of the quotient is derived by extrapolation.Zusammenfassung1.Einfache statistische Variabilitätsmaße sind u. a. wegen der nicht normalen Verteilung der Momentanpulsfrequenzwerte zur Beschreibung der Arrhythmie wenig geeignet.2.Ein Arrhythmie-Maß muß sowohl die Schwankung der Pulsfrequenz nach Größe als auch nach Häufigkeit berücksichtigen.3.Der abgeleitete Arrhythmie-Quotient nimmt mit der Arbeitsschwere sowie der Pulsfrequenz ab. Es läßt sieh eine extrapolierte Restarrhythmie angeben, die der stochastischen Komponente der Arrhythmie entspricht.

Work measurement Psychological and physiological techniques for assessing operator and work load

Abstract This paper deals with analysis of man—machine systems by asking for the essential task clone by the subsystem ‘ operator ). By using the method of block-box analysis static and dynamic characteristics of the subsystem can be found. Different research methods are discussed. Practicable methods should not influence the work situation, therefore a telemetric registration should be preferred. Examples for analysis of heavy work load, senso-motoric and mental tasks are given.

Erweiterung der Beurteilungsmethodik von Kraftmessungen bei der arbeitsmedizinischen Begutachtung

SummaryThe value of measuring of muscular forces in confirming the diagnosis of an impediment depends on the motivation of the subject. Therefore this is a controversial method. An improvement of the measuring of muscular force is presented, using electrical activity (EMG) and its variations as a control instrument to determine motivation. The functional relationships between the electrical activity, its variations, and the muscular forces form the basis of this method. A representative medical report is presented to demonstrate the application of the methods proposed.ZusammenfassungZu der oft kontrovers diskutierten Möglichkeit der Anwendung von isometrischen Kraftmessungen zur Beurteilung einer Behinderung bei medizinischer Begutachtung wird ein Vorschlag entwickelt, entsprechende Kraftmessungen nach der indirekten Methode nach Rohmert & Sieber (1960) durch die Auswertung des zeitabhÄngigen Verhaltens des OberflÄchenelektromyogramms zu ergÄnzen. Aufgrund zur Verfügung stehender funktionaler Beziehungen zwischen der VerÄnderung der aus dem Elektromyogramm abgeleiteten elektrischen AktivitÄt und der abgegebenen relativen Kraft bei statischen Kontraktionen können MaximalkrÄfte ermittelt werden, die mit den durch direkte oder indirekte Maximalkraftermittlung gewonnenen Werte verglichen werden können.Die Anwendung dieses Vorschlags wird an einem Beispiel einer gutachterlichen Fragestellung demonstriert. An dem Beispiel wird darüber hinaus eine Möglichkeit demonstriert, nÄherungsweise Aussagen zur statistischen Sicherheit im intraindividuellen Vergleich zu machen, wenn ein Mittelwert mit einem Einzelwert verglichen werden mu\.

Ergonomic research in German travelling mail service: Part 1: Ergonomic problems and research in railway mail vans

Ergonomic problems in the travelling mail service are described, showing the necessity of ergonomic research work within the railway mail van, to obtain results suitable for evaluating the strain of travelling mail office clerks as well as for designing the system of a mail railroad car. The special methodological procedure of this type of ergonomic field research is discussed.

Serienkorrelation physiologischer Zeitreihen und deren Bedeutung für die Beanspruchungsanalyse

After preliminary consideration of the phenomenon of serial correlation, the effect of serial correlation on the significance of correlation between serial correlated time series is discussed.Using results of heart rate registrations of radar controllers the methods for correlating serial correlated time series are demonstrated.Final general considerations using the results of the examples should help in dealing similar problems of work physiology.ZusammenfassungNach einleitenden Erläuterungen zum Phänomen der Serienkorrelation wird deren Bedeutung für die Signifikanzprüfung der Korrelation zwischen serienkorrelierten Zeitreihen diskutiert.An Untersuchungsergebnissen des Pulsfrequenzverhaltens von Radarlotsen werden quantitative Verfahren zur Berücksichtigung des Serienkorrelationseffektes vorgestellt.Aus einer verallgemeinernden Betrachtung der aus den Beispielen gewonnenen Ergebnisse ergeben sich Schlußfolgerungen für die Behandlung ähnlicher arbeitsphysiologischer Fragestellungen.

Ergonomic research in the German travelling mail services Part 3: Consequences for system design

The work process within a railway mail van is analysed showing that only 4 of 14 processes are technological ones, ie specific to the mail operation. The flow of material within todays vans is very confused. For the given technical data a new design was developed using line arrangements and separated work places with specific work content. The design allows a reduction of travelling mail service staff of about 30%, with an increased system effectiveness and less stressful working conditions for the clerks.

Ergonomic research in the German travelling mail services Part 2: results of ergonomic research in railway mail vans.

The travelling mail office clerks are shown, by medical examination and sociopsychological questionnaire, to be a very homogeneous naturally self-selected group with a low average age. The analysis of tasks shows a disadvantageous distribution of some main tasks over the work shift. Energy expenditure and cardio-vascular strain above physiological endurance limits occur mainly with the tasks of loading, handling and emptying mail bags. Environmental factors are mainly within acceptable standards. Fast-time simulation studies show that proposals can be made for organisation work (by job rotation) and selection of TMO clerks based on their individual working capacity.

Analyse von Zeitreihen physiologischer Meßgrößen durch Korrelationsfunktion und Leistungsspektrum

SummaryAfter a preface concerning the term “time series” the difficulties of investigation physiologic time series are pointed out. The principles of correlation function and power spectrum and the methods of calculation are presented. — Their characteristics as applied method for investigation of physiologic time series are demonstrated in examples.ZusammenfassungNach der einleitenden Erläuterung des Begriffs der Zeitreihe wird auf die Schwierigkeit der Analyse von physiologischen Zeitreihen mit konventionellen Methoden hingewiesen. Die Grundlagen zur Berechnung von Korrelationsfunktion und Leistungsspektrum werden dargestellt; die besonderen Eigenschaften erlauben die Anwendung als Analysenmethode zur Beschreibung physiologischer Zeitreihen. — In Beispielen wird die praktische Anwendung demonstriert.