A search algorithm is presented to generate all shift systems according to a given set of constraints, including physiological and social requirements. The generated shift systems are weighted according to such criteria as the time distribution of the shifts, the length of the weekend leisure time and the regularity of the shift system. The use of this algorithm is restricted to the construction of shift systems for a maximum of five crews, as is usual in industry. A heuristic algorithm for the construction of more complex shift systems, as used in the services sector, is also described. The user of the program may consider all criteria simultaneously. He must assign priorities to the criteria according to his wishes.

Journal Article↗

PubMed1986

Longitudinal approach to assessing maximal aerobic power during growth: the European experience.

This review deals with the principle and constraints of conducting longitudinal studies on exercise in children. As with cross-sectional studies, longitudinal ones have advantages and constraints: the different types of such designs as mass studies, population studies, or prospective cohort studies should be therefore selected to minimize their possible drawbacks. Other problems of longitudinal studies, such as the age span studied, time and sequential measurement effects, or interventional effects, have to be controlled by statistical measures and study design. In longitudinal studies ad hoc research groups working in field laboratories are for many reasons more flexible than permanent teams using institutional laboratories. Only direct determinations of maximal aerobic power should be used in longitudinal studies. These should be accompanied by such measurements as body height, body mass, lean body mass, and peak height velocity and by such health indicators as daily physical activity, blood pressure, smoking habits, and blood lipids. Examples for this approach are given in this paper, and general issues of longitudinal studies are discussed from the economic and ethical point of view.

Adolescent↗

PubMed1986

Ethical considerations: the participation of children in elite sports.

In a way, children involved in elite sports can be considered participants in an uncontrolled mass experiment with human beings. Sports have many benefits for children, especially when this activity is compared with the sedentary life styles of too many children all over the world. However, training in such sports is progressively becoming more prevalent in an earlier age in childhood, and potential risks of musculoskeletal disorders or diseases, social isolation to a restricted group with similar interests, and the psychologic stress of repetitive and monotonous sports activities for several hours each day, are concerning physicians. Added to these concerns are the dangers associated with hormonal and dietary manipulations practiced by athletes in elite sports. Ethics committees to control training procedures of gifted children and to propose higher age limits for participants, especially in international sports events, seem to be needed. Long-term effects of elite sports activities beginning in early childhood should be studied using appropriate epidemiologic methods. The basic ethical consideration is not to harm or alienate children by using them as objects for sports organizations, spectators or nationalists.

Adolescent↗

PubMed1985

Favourable levels of cardio-vascular health and risk indicators during childhood and adolescence.

This paper is concerned with favourable levels of constitutional cardio-vascular health indicators during childhood and adolescence. A cross-sectional randomised sample of healthy Czechoslovakian children was investigated, because this population is habituated to a favourable life style. Twenty girls and 20 boys at ages 8, 12 and 16 years were recruited to the study. Statistical data for means and standard deviations are presented with regard to maximal aerobic power, haemodynamic variables such as arterial blood pressure, heart rate at submaximal and maximal muscular exercise, body fat content, blood lipids including total cholesterol and its fractions, high- and low-density lipo-proteins, fasting triglycerides and the apo-lipo-protein profile. The maximal oxygen uptake in absolute values increased with age in both sexes and the boys appeared to average higher than the girls at each age. When maximal aerobic power was expressed on a total body weight basis, boys appeared to average higher at age 16 years (56 ml X min-1 X kg-1) than girls (45.8 ml X min-1 X kg-1). The highest recorded heart rate for ergometric work averaged close to 200 min-1 in both sexes with no significant age differences. The diastolic blood pressure at rest did not change significantly with age or sex. Serum cholesterol levels were found to decrease significantly after puberty in boys (post-pubertal dip), but in the girls there was found no systematic change in mean values with age. When HDL was expressed as a percentage of total cholesterol there appeared to be no differences related to age and sex.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1985

Energy expenditure constrained by sex and age.

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Adolescent↗

PubMed1985

Circulatory and respiratory responses to muscular exercise in Czech and Norwegian children.

This paper presents a comparison between Czech and Norwegian rural healthy children with regard to the functional characteristics of the circulatory and respiratory system based upon work physiological variables and measurements of some pulmonary volumes. The study included randomised samples of boys and girls at the age of 8, 12 and 16 years, 66 Czech boys and 63 girls, 54 Norwegian boys and 57 girls. At the age of 8 years the maximal aerobic power was closely similar in both countries, but in the older age groups the Norwegian children exhibited lower physical fitness. The maximal heart rate was close to 200 min-1 on the average without any sex, age or ethnic differences. In agreement with the higher maximal aerobic power the 12 and 16 year old Czech children had lower submaximal heart rates for the same oxygen uptake than the Norwegian children. The forced vital capacity and forced expiratory volume in one second was significantly higher on the average in Czech than in Norwegian children but the latter, expressed in percent age of the former, averaged 87 to 91% without any sex, age or ethnic differences. The maximal ventilation volumes during muscular exercise reached higher values in Czech than in Norwegian children of the same age, but the mean maximal respiratory rate was close to 60 min-1, being independent of age, sex and cultural differences. During heavy exercise only 40 to 50% of the vital capacity and 45 to 55% of the forced expiratory volume were taken into account and this index of pulmonary function did not differ with sex, age or ethnic differences.

Adolescent↗

PubMed1984

Adjustment of the oral temperature rhythm to a fixed watchkeeping system on board ship.

Oral temperature data were collected from 12 members of the crew of an oil tanker at sea. Most of the personnel examined were engaged on watchkeeping duties on a '4 on, 8 off' fixed-hours system; the remainder included 3 "day-workers". The study commenced after the subjects had been following their particular work schedules continuously for several weeks, thus providing good opportunity for adaptation to them. Observations were made at 4-hourly intervals during waking hours, over a period ranging from 8 to 13 days in individual cases. The form of the mean curves produced by averaging the readings over all days indicated that a reasonable degree of adjustment of the temperature rhythm to the different sleep/wake routines imposed by the work system had occurred. Estimates of rhythm phase and amplitude obtained by "single cosinor" time series analyses of the sequential data supported this impression. However, further investigations are needed to substantiate these findings, and also to determine how long it takes for the rhythm adjustment process to reach completion in inexperienced workers.

Body Temperature↗

PubMed1984

Influence of coffee on the excretion of noradrenaline and adrenaline in urine. A pilot study for the comparison of two methodical models.

In field studies, the excretion rate of urinary catecholamines is very often used as an indicator of strain. Interfering effects which are due to caffeine, for example, can only be quantified if the influence of coffee consumption on the excretion of catecholamines is known quantitatively. This was the aim of our study with five subjects, on five consecutive working days, and with a strict standardization of nutrition. The urine samples were specified with respect to the following parameters: sampling period, volume, urine status, density, creatinine, noradrenaline, and adrenaline. Adrenaline showed a significant correlation with coffee consumption, whereas noradrenaline did not. Moreover, it could be demonstrated that relating the concentration of catecholamines to the creatinine excretion is insufficient for work physiology studies, especially if the urine sampling periods are as short as 2h.

Adult↗

PubMed1984

The growth of lung volumes affected by physical performance capacity in boys and girls during childhood and adolescence.

The paper concerns a longitudinal study of the relationship between growth in lung functions in terms of forced vital capacity and forced expiratory volume in 1 s, and the development of maximal aerobic power during the age span from 8-18 years of age. The growth curves of anatomical dimensions for boys and girls were similar to those previously established for Northern European children. The growth in lung volume ended later than the growth in body height. It was found that the growth in lung volume was entirely due to growth in body dimensions, with no additional effect of changes in the development of physical performance capacity.

Adolescent↗

PubMed1984

Leisure time sport activities and maximal aerobic power during late adolescence.

The pattern of leisure time sport activity was estimated by retrospective recalls and expressed in terms of an annual sport activity score. The activity score was related to the development of maximal aerobic power during the period of late adolescence in German children. Both girls and boys reduced their activity pattern from 14 to 18 years of age, boys more than girls. At each age boys were more active than girls. A slight tendency towards better fitness with increased habitual physical activity was noticed, but many sedentary children exhibited a good performance capacity and some children with a high level of leisure time sport activity were characterized by a low level of maximal aerobic power. A statistical analysis revealed that the observed tendency to better fitness with increased habitual physical activity could be explained by an age factor with no additional effect of variation in sport activity score.

Adolescent↗

PubMed1983

Reduction of nightwork by re-designing of shift-rotas.

The reduction of nightwork is an important preventive measure to limit possible negative effects of night shifts on well-being, health and social life. An example of a gradual reduction of nightwork in a group of transport workers at an airport is presented. After having carefully analysed the real number of persons needed during nighttime for loading and unloading aircrafts the number of shiftworkers who had to work between 02.00 and 06.00 h was reduced in a first step from 104 to 66 and in a second step to 38 persons.

Aircraft↗

PubMed1983

Time-budget studies of policemen in weekly or swiftly rotating shift systems.

For 8 days 120 policemen kept special diaries including working time, travelling to and from work, leisure time and sleeping time. By analysing the data of leisure and sleep in relation to the time of day and the type of shift it is possible to find out critical points within a shift system. The mean duration of sleep was reduced before morning shifts, between night shifts and after a morning shift that was followed by a night shift on the same day. The leisure time was limited in connection with afternoon shifts and between the combined morning and night shift. It is recommended not to have double shifts on one day. Rapidly rotated shift systems had more advantages referring to the total amount of night sleep than weekly rotated shift systems. The backward rotation of shifts was unfavourable because of the short time off between the last afternoon shift and the first morning shift. Furthermore, short nightwork periods and a start of the morning shift which is not too early seem to be preferable.

Journal Article↗

PubMed1983

Analysis of 120 shift systems of the police in the Federal Republic of Germany.

120 shift rotas of the police were collected and analysed. The frequency distribution of the shift cycles, the duration of shifts, the start and end of shifts, the maximal number of consecutive night shifts, as well as the frequency of different kinds of free weekends, were determined. The shift systems are compared with recommendations for the design of shift rotas which are based on physiological, psychological and social criteria.

Journal Article↗

PubMed1983

A calculation and interference test apparatus for the simulation of mental stress.

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Data Display↗