[Comparison of the physical fitness of the young population of Czechoslovakia with similar data from other European countries]. / Srovnání telesné zdatnosti nasí mladé populace se stejnými údaji nekterých evropských státu.

In order to analyze the relationship between VO2 max and height, body mass and lean body mass a multi-longitudinal survey was conducted on three different age groups of randomly selected children from a small Czech community. Beginning at the initial ages of 8, 12 and 16 years subjects were subsequently retested three times at two year intervals. At overlapping ages there were no differences in the various age groups between height and VO2 max. By utilizing mean values for the various parameters at specific calendar ages a growth curve was constructed for each sex for the age range 8 to 20 years. The values were compared with longitudinal studies of various countries and no substantial differences were found. When VO2 max was then compared to height, body mass and lean body mass it was apparent that the almost linear relationship with height was the most precise. In addition the children remained, generally speaking, in their same rank order for VO2 max for the three different age groupings.

The relationship between changing body height and growth related changes in maximal aerobic power.

In order to analyse the relationship between maximal aerobic power (VO2max) and height, body mass and lean body mass a multi-longitudinal survey was conducted on three different age groups of randomly selected children from a small Czech community. Beginning at the initial ages of 8, 12 and 16 years subjects were subsequently retested three times at 2-year intervals. At overlapping ages there were no differences in the various age groups between height and VO2max. By utilizing mean values for the various parameters at specific calendar ages a growth curve was constructed for each sex for the age range 8-20 years. The values were compared with longitudinal studies in various countries and no substantial differences were found. When VO2max was then compared to height, body mass and lean body mass it was apparent that the almost linear relationship with height was the most precise. In addition the children remained, generally speaking, in their same rank order for VO2max for the three different age groupings.

A comparative study on different methods for the determination of energy expenditure.

In order to determine energy expenditure, the Douglas Bag technique (DB) and Kofranyi-Michaelis respirometers (KM) have been widely used under field conditions for several decades. Some years ago the Oxylog (OX) method was developed, measuring simultaneously the difference of partial oxygen pressure in inspired and expired air (PO2 diff.) by two polarographic oxygen sensors. In order to compare these three methods laboratory experiments (3 test subjects, 5 different bicycle ergometer work loads, 180 measurements per apparatus) were performed. Oxygen uptake (VO2) varied between about 0.9 to 3.0 l/min. The VO2 data obtained by the DB method, which were used as a reference, and those obtained by the KM method agreed fairly well. The recorded data of OX underestimated VO2 up to 21%, with the deviation increasing with work intensity. A sufficient accuracy of recorded VO2 was observed only up to moderate work intensity. OX data calculated from ventilation volume of inspired air per minute (VI) and PO2 diff., measured by OX, were always about 19% higher than those recorded by OX. This means that the calculated VO2 values of the OX corresponded fairly well with DB values at heavy work loads. The reason for the differences between recorded and calculated OX data is still unknown. Further research is urgently needed.

Volume calibration of various gasmeters using a modified Tissot spirometer.

Various methods for determinating energy expenditure by indirect calorimetry are used in laboratory and field studies such as the Douglas bag method, often used in combination with a wet gasmeter, the respirometer of Kofranyi and Michaelis (KM) and the Oxylog (OX). To calibrate the volume measurements of these pieces of apparatus a modified Tissot spirometer was built, consisting of an outer casing filled with water, a core and a bell. It was equipped with a solid counterbalance and with an additional roller chain, partly freely suspended on the side of the counterbalance. This construction allowed compensation for the varying buoyancies of the bell. The lift of the bell was measured by means of a vernier scale. From calculations of the geometric volume a revolution counter was adapted to record the moved volume in litres. By means of this spirometer volumes up to 200 l can be used for calibration at various physiological flow rates. Calibration procedures for KM, wet gasmeters and OX were developed. For OX a small inaccuracy up to 2.0% was observed within the flow range from 20 to 70 l.min-1. The inaccuracy increased at higher flow rates. Under defined calibration conditions the modified Tissot spirometer enabled repeated calibrations of different types of gasmeters.

Combined effects of shiftwork and environmental hazards (heat, noise, toxic agents).

The paper deals with the results of studies or discussions concerning the problem of nightwork combined with other adverse working conditions. Special emphasis is laid on the untoward effect of high temperature during nightwork, as well as on noise and exposure to chemicals. It is shown that there is no substantial influence of heat stress on the circadian rhythm of adrenaline excretion under sitting working conditions with the subject performing a difficult mental task at warm climates up to 30 degrees C BET. Shiftwork and noise induce independent different effects which can be explained in terms of activation for shiftwork and in terms of tension for noise. The combination of both adverse exposures is therefore partly subtractive but partly additive as night work and noise negatively affect daysleep. Practical experience in the field of combined effects of shiftwork and chemical agents is lacking, but theoretical speculations lead to the conclusion that there may exist a time of day dependence of some chemicals, used at workplaces.

Subjective health status of day and shift-working policemen.

To assess the subjective health status of day- and shift-working police officers, a questionnaire-based study was carried out. All the day-workers had previous shift experience. To control the age factor the total population of 2659 shift-working and 1303 day-working police officers was divided into four ten-year age classes. Factor analysis revealed that all the symptoms included in the questionnaire could be grouped into six factors. The prevalence rates of complaints showed that four of these factors (autonomous symptoms, musculo-skeletal symptoms, disturbance of appetite and indigestion, respiratory infections) were influenced by the main effects of age and shift work. Across all age classes the age-related changes in prevalence rates were strengthened by shift-work. In the other two factors (nervous symptoms, gastro-intestinal symptoms) an additional interaction effect could be observed. While the prevalence rates of the day-workers increased with age, those of the shift-workers decreased in the oldest age class. This drop of prevalence rates may be attributed to the influence of selection processes.

Exercise physiology: health indicators and cardiovascular risk factors during childhood and adolescence.

Low risk strategies use favourable levels of different behavioural and physiological parameters, which may be accepted as health indicators. High risk strategies are oriented to protect people from the potential risk levels of the same behavioural and physiological parameters. Both strategies are first applied to adults; but the established levels of risk in adults cannot be explained only by their living conditions, these factors must have some genetic and educational roots in childhood and adolescence. Based on several cross-sectional and longitudinal studies of 1652 subjects it was shown that trained and untrained adolescents did not differ in family history of CHD but clearly had different behavioural risk factors. The early identification of children and adolescents with a high risk of developing CHD should be intensified using integrated risk indicators. Thus collaboration between exercise physiology and preventive cardiology should be centered more on studies of children and adolescents.

Acute toxicity of benzene in rats at different periods of day and in different light/dark regime.

Acute toxicity of benzene expressed by survival time and mortality percentage of rats varied in circadian manner. Survival time of rats maintained under standard light/dark (L/D) conditions was significantly shorter when benzene was injected at 20.00 or 24.00, than at 08.00. Simultaneously, mortality of rats was reversed. Inversion of L/D regime of exposure to continuous light abolished all those effects. Rats exposed to continuous darkness showed significantly longer survival time when benzene was administered at 12.00 or 24.00 than when it was injected at 04.00. Generally, acute toxicity of benzene in rats exposed to light was markedly less pronounced than in animals exposed to darkness.

[Effect of performance and state orientation on achievement and attention indicators in a simple stimulus-response task with and without performance feedback]. / Der Einfluss von Handlungs- und Lageorientierung auf Leistungs- und Beanspruchungsindikatoren bei einer einfachen Reiz-Reaktionsaufgabe mit und ohne Leistungsrückmeldung.

In formulating his theory of action control, Kuhl (1983) proposed two motivational states: action orientation and state orientation. People who are action oriented are able to ignore all informations in concrete situations which are irrelevant with regard to the preferred goals. Persons who are state oriented tend to focus sooner on the outlast aspects of a special state. Kuhl introduced a questionnaire HAKEMP to record these tendencies. Further on, there occurs the general assumption that in a particular state of state orientation, people have only a limited processing capacity for given tasks. This hypothesis was tested in an experiment (n = 88) with a stimulus-reaction task. The conditions were varied by the type of the task (fixed or variable stimulus interval) and feedback for the subjects' ability to react. It was expected that for the fixed stimulus interval condition, state-oriented people would be less efficient than action-oriented subjects; with feedback there should be increasing results. The experiment however, shows no significant difference between the performance of state- and action-oriented subjects. These results are discussed in relation to modifications of the HAKEMP questionnaire.

A comparison of coronary risk factors in groups of trained and untrained adolescents.

Fifty-five experimental (29 male, 25 female) and 38 control (20 male, 18 female) adolescent subjects participated in this study to investigate the differences in coronary heart disease (CHD) risk factors in groups of trained and untrained adolescents. As expected the trained group (both sexes) had higher maximal aerobic power (VO2max) and lower systolic blood pressure at rest. The level of total cholesterol was the same in both groups, but the levels of high-density lipoprotein and its lipoprotein subfractions apolipoprotein (Apo-A) and Apo-A1 were higher, and low-density lipoprotein, Apo-B and triglycerides were significantly lower in the experimental group. The value of risk factors from the family history was the same in both groups, but the behavioural and physical risk factors such as smoking and percentage of body fat were lower in the trained group. It would appear that the group of adolescents, trained for several years in athletics and swimming, had a more beneficial lipoprotein profile and a lower level of behavioural and physical risk factors than the control group. For methodological reasons it remains an open question whether these profile differences are the consequences of self-selection procedures or the effects of training.

[Stress and strain analysis in monitoring functions in a fully automated production plant]. / Belastungs- und Beanspruchungsanalysen bei Uberwachungstätigkeiten in einer vollautomatisierten Fertigung.

The introduction of new technologies in the automobile industry produces a substantial structural change. This change may lead to a decrease in physical work with a contrary increase in mental and emotional stress at monitoring and controlling tasks. A summarizing analysis of the stress was made by means of the "Arbeitswissenschaftliches Erhebungsverfahren zur Tätigkeitsanalyse (AET)" and for characteristic working conditions the energy expenditure during work was measured. As indicators of strain, the heart rate was registered continuously with portable magnetic tape recorders and additionally the urinary excretion of adrenaline and noradrenaline was analyzed. During and after the implementation of new technologies a shift from physical to mental and/or emotional stress could be observed, but the remaining components of physical load are not to be disregarded and the changing strain patterns have to be analyzed carefully during the transitional stages of the implementation process.

Work at sea: a study of sleep, and of circadian rhythms in physiological and psychological functions, in watchkeepers on merchant vessels. II. Sleep duration, and subjective ratings of sleep quality.

Sleep length and sleep quality scores were collected on board ships over periods of up to two weeks from 38 watchkeepers working a '4-on/8-off routine' and 29 dayworkers. All watchkeepers exhibited fragmented sleeping patterns, which indicated a lack of adaptation of the sleep/wakefulness cycle to the hours of work. There were only slight differences in total sleep length between watchkeepers and dayworkers, however, both groups did not obtain an adequate amount of sleep. Within the watchkeeping crews the 3rd Officers had by far the shortest sleep length. Concerning sleep quality, daytime sleep was generally given the lowest ratings, whereas sleep starting before midnight was on average evaluated as the best, both by watchkeepers and dayworkers. Watchkeeping personnel do not normally have any "days off" during a voyage so that missed sleep might even amount to a sleep deficit. A solution for this problem could perhaps be a new, stabilized system that allows a single uninterrupted sleep, which is required for full recuperation, to be taken each day.

Work at sea: a study of sleep, and of circadian rhythms in physiological and psychological functions, in watchkeepers on merchant vessels. III. Rhythms in physiological functions.

Oral and rectal temperature, urinary excretion of adrenaline and noradrenaline, and heart rate were measured in 28 watchkeepers working a "4-on/8-off" routine, and in 25 dayworkers, on board ships. Readings of oral temperature were taken over 4-hourly periods of up to two weeks; the rectal temperature, urine, and heart rate data were collected on selected days within these periods. Analysis of watchkeepers' temperatures and unconjugated catecholamine excretions showed slight signs of an interactive adaptation to time of day and hours of work, but it was clear that full phase adjustment of the circadian rhythms to shifted hours of work did not occur. The "split" pattern of sleep imposed by the watch system may be a major factor in preventing complete adaptation of physiological rhythms to shift work in the shipboard situation; this problem could be overcome by devising a system that allows sleep to be taken in a single uninterrupted block each day.

Work at sea: a study of sleep, and of circadian rhythms in physiological and psychological functions, in watchkeepers on merchant vessels. V. Effects of time zone crossings.

Daily diary records of sleep and activity, and 4-h measurements of body temperature, performance and subjective alertness were collected on board ship from 15 watchkeepers on the 4-on/8-off system, and from 28 dayworkers, on both westward and eastward transatlantic voyages. The data from a balanced sample of the subjects were analysed over selected 8-d periods of the voyages where four or five time zones were crossed. During these periods the average amount of daily sleep obtained by dayworkers on the eastward voyage was more than 1 h less than that on the westward voyage, and its quality was rated lower. Watchkeepers' main sleep was also shorter when travelling eastward, but this reduction was partially compensated for by a slightly longer secondary sleep. With the exception of subjective alertness on the eastward voyage, the basic phase of the circadian rhythms in the measured variables adjusted appropriately to the clock changes associated with the time zone crossings. The normal shape of the average daily curves was, however, altered differentially in the two directions of travel; as a result, morning levels of all variables were lower on the eastward voyage than on the westward, but evening levels were higher. These distortions of rhythm waveforms, which probably arose from a combination of endogenous and exogenous factors, add another dimension to the basic problem caused by the effects of circadian rhythms on operational efficiency in the shipboard situation. This problem can only be solved by the development of alternative watchkeeping systems which take full account of these rhythms.

Comparison of two analytical procedures for the determination of free urinary catecholamines under the demands of shiftwork experiments.

A typical shiftwork experiment was chosen to prove the validity of an automated procedure for the analysis of free noradrenaline and adrenaline in urine. The method consists of a column switching technique with an adsorption/elution clean-up and a reversed phase high performance liquid chromatography followed by chemical reaction detection based on the trihydroxyindole method. The analysis of variance was performed using a second data set obtained by a semi-automated procedure for which the accuracy had already been confirmed. The analysis of covariance showed that for field studies, as well as for laboratory experiments in which the variances contributed by the experiments themselves are greater than 10% rel., the data sets of the two methods provide the same information.