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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.

Zusammenfassung: 956 Arbeiter des Hüttenkombinats, die schwere körperliche Arbeit von Grad 2, 3 bzw. 4 leisten, wurden in einer epidemiologischen Querschnttstudie mittels eines Fragebogens über subjektive Beschwerden, hauptsächlich an der Wirbelsäule, befragt; bei 136 von diesen Arbeitern wurde zusätzlich eine Röntgenuntersuchung durchgeführt. Prävalenz von Rückenbeschwerden bestand bei durchschnittlich 51, 2 %, sie korrelierte signifikant mit ätiologischen Faktoren wie Alter, Berufsalter, früherer Lendenwirbelsäulenverletzung, Ausbildungsniveau, sportlicher Betätigung, Arbeitsintensität, körperhaltung bei der Arbeit, Zufriedenheit mit den Produktions- und Arbeitsbedingungen und Hausarbeit. Unter den ätiologischen Faktoren konnten durch die Multifaktor-Analyse schwere körperliche Arbeit und ungünstige Körperhaltung den übrigen vorangestellt werden, und die Hypothese, daß schwere körperliche Arbeit ein wichtiger Faktor ist, wurde durch die Röntgenuntersuchung gestützt.

The 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.

1.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.

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 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.

After 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.

Information content analysis based on information theory can be used to evaluate stress in controllers. The method is applied to the analysis of radiotelecommunication in air traffic control: ' message types ' are defined and their information content is evaluated using the syntactic level of information. Related to time, the measurements of information provide a stress factor. Preliminary results indicate the usefulness of the method.

A short system analysis of the air traffic control systems with respect to their purpose and realization shows the role which the human operator plays. The task of man in this system can be determined as information processing. Evaluation of these tasks is important for selection of personal, for job evaluation, and for redesigning tasks and jobs in order to fulfill the tasks of ATC in future. This evaluation of man's tasks can be regarded either from the demands of the job or from their fulfillment and effect for man. Both aspects have to be connected to get objective results which are valid for man. Special research problems arise from the influence of the individual abilities and from the correlation of stress as work load factor and strain as effect of this work load on man.