Validation of a questionnaire for assessing physical work load.

OBJECTIVES: Reliable, valid, and compatible methods are required for exploring the complex interactive effects of psychosocial and physical stressors on complaints and disorders. An instrument for assessing physical work load that integrates information from a biomechanical model of lumbar load is presented and validated. METHODS: Four hundred and fifty-five people working in nursing homes for elderly people in Germany filled out the developed questionnaire 3 times within 1 year. Test-retest reliability was calculated, and validity was checked several times. Relationships with other, theoretically related and unrelated variables were examined. RESULTS: The test-retest reliability of the questionnaire measures was about 0.65. The convergent and discriminant validity was satisfactory, and the questionnaire was able to separate professional subgroups with different physical work loads. The Spearman rank-order correlations between physical load and musculoskeletal complaints were about 0.30. CONCLUSIONS: The method developed in this study is a reliable and valid instrument for assessing physical work load. The integration of statistical methods from psychological testing and theory in the development of methods exploring the effects of physical work load is advocated.

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.

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.

[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.

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)

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.

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.

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.

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.

Maximal aerobic power affected by maturation and body growth during childhood and adolescence.

This paper examines the development of maximal aerobic power as a function of maturation by a longitudinal study with annual examinations of representative samples of 56 boys and 56 girls in Norway and Western Germany. The age at which occurred peak height velocity (PHV) (i.e. the age at which the greatest height velocity was observed) was used as a reference of biological age and maturation. Before the PHV the mean maximal aerobic power was the same in two cohorts of children both in absolute values as well as in values relative to total and lean body mass. At and after PHV the boys were similar in their absolute values, but the German girls decreased their exercise fitness and became inferior to the Norwegian girls during later adolescence. When related to age of PHV the maximal aerobic power increased during the prepubertal years, mainly as an effect of growth in body size with little or no additional effect of other factors and approached a ceiling level at the end of adolescence. The boys exhibited clearly superior exercise fitness during all years of childhood and adolescence, this being in contrast to the widely accepted concept that no sex difference exists in exercise fitness before puberty. The maximum level for VO2-max, reached at the end of adolescence, averaged 3.2 1/min with a coefficient of variation of about 12% for the boys, and 2.5 1/min for the Norwegian girls and a similar coefficient of variation. As these ceiling values of maximal oxygen uptake agree with published averages for normal young adults representative for the normal population in these two countries, it is suggested that they represent optimal values brought about mainly by normal growth in body size with no or little additional effects of other factors.

Maximum aerobic power and body composition during the puberty growth period: similarities and differences between children of two European countries.

This report gives results of a longitudinal study of two cohorts of school children in Norway and West-Germany. The rate of growth in body size and composition is identical for the two samples, but different for the two sexes, and follows closely the trend of growth which has been found for North-Europeans in general. Despite of this similarity in growth of anatomical variables the Norwegian children appeared to be superior in their maximum aerobic power at all comparable ages and in both sexes. The differences between means in maximal oxygen uptake varies somewhat with age and sex and are in the range of 5-10%. It is suggested that the mean differences between Norwegian and German children in their exercise and cardio-vascular fitness are brought about by a more physically active behavioural pattern of living in Norway.

Excercise ventilation during the growth spurt period: comparison between two European countries.

The paper provides reference values with regard to pulmonary ventilation responses o progressively increasing bicycling up to the maximal level during the period of growth spurt. Data are based on longitudinal studies or rural Norwegian and German school children. A cluster sampling technique was used, starting with the total pupil-population at Lom in Norway at an age of 8 years, and annual tests were performed until the age of 15 years. In germany a similar pupil-population was tested from age 12 until age 17 years. Functional growth curves giving means and dispersions for ventilation rates, tidal volume, respiratory frequency, ventilatory equivalent and respiratory gas exchange ratio are constructed. Norwegian and German children's developmental processes with regard to the exercise ventilation variables were compared, and revealed no significant differences.

[Studies on differences in the preventive effects of habitual physical activity in occupation versus leisure time. II. Effects of physical activity in occupation versus leisure time on physical working capacity (author's transl)]. / Untersuchungen über unterschiedliche präventive Effekte von habituellen körperlichen Aktivitäten in Beruf bzw. Freizeit. II. Die Wirkung von körperlichen Aktivitäten im Beruf bzw. in der Freizeit auf die kardiopulmonale Leistungsfähigkeit.

One hundred and twenty men, aged 23--60 years and having various professions participated in studies on relationships between daily physical activity and physical performance capacity (PPC). The determination of daily physical activity at work and of the habitual leisure time activities has been described earlier (Ilmarinen et al. 1980). The determination of physical performance capacity was based on W170, W85% and on predicted VO2 max measured with continuously increasing work load on a bicycle ergometer. The W85% modification corresponds to the working capacity at a heart rate level of 85% of maximal heart rate. Workers with a combination of heavy physical work and active leisure time showed systematically the highest absolute and relative values of PPC. However, although the results indicated that the effect of work activity on PPC was not significant, the effects of leisure time activities on W85% and on VO2 max related to lean body mass were significant. It is concluded that the leisure time sport activities are more important than the physical activity at work in maintaining or increasing the PPC. Aerobic sport activities in leisure time are recommended both for persons with physically heavy and light work.

[Occupational health studies on airport transport workers. I. Results of ergonomic time and motion studies (author's transl)]. / Arbeitsmedizinische Untersuchungen über Ladearbeiten auf einem Grossflughafen. I. Ergebnisse arbeitsphysiologischer Zeit- und Positionsstudien.

Loading and unloading of aircrafts involves lifting, moving, and carrying of heavy cargo in unfavourable body positions and in narrow spaces. This transport work was subjected to an investigation in a big airport. Forty-three male transport workers and foremen were studied during 46 total shifts. The type of activity was recorded by using the standardized procedure, the so-called "Arbeitswissenschaftliches Erhebungsverfahren zur Tätigkeitsanalyse" (AET). For time and motion analysis, body positions were recorded by continuous observation during the total shift. For typical activities the energy expenditure was determined. The strain caused by transport work was estimated by recording the heart rate with a portable cardiocorder during the total shift. The results show that both dynamic and static work are involved in the loading and unloading of aircrafts. The heart rate varied characteristically according to the body position and to type of activity. The body position was mainly determined by the height of the bellies (from 0.61-1.97 m) of different aircrafts. An additional influence due to weight carrying could be observed only in body positions with low energy expenditure. Recommendations for changing the height of the bellies or to the appropriate selection of workers were made.

[Experiences with a cardiorecorder system for continuous 24-hour registration of heart rate]. / Erfahrungen mit einem transportablem Gerät zur kontinuierlichen registrierung der Herzfrequenz für Zeiten bis zu 24 Stunden

Studies regarding to the continuous registration of the heart frequency by a transportable instrument, which can store the data of the heart frequency per minute up to 24h, are presented. It is a tape recorder the speed of which is geared down. Thus a normal tape cassette C 60 is sufficient for a registration of the heart frequency during 2 X 24h. The R-wave of the ECG is registered on the first channel of the tape as a biological signal. Moreover every minute an impulse of a clock is recorded on the second channel of the tape. With help of a second instrument the play back procedure for the 24-h-recording can be performed in about 15 min. The signals of both channels of the tape are transformed in digital rectangle impulses by an installed impulse-converter. The serial impulses are counted per minute with help of the time-mark by an interface in a counter. These data are at disposal in BCD-code. They can be passed on the following peripherals: digital printer, computer, pen-recorder and so on. A parallel standardized recording of the physical activity observed by the subject or by an experimenter allows a statistical evaluation and comparison of the physical activity with the corresponding heart frequency data. Some examples of the aread of occupational health, epidemiology and exercise physiology are discussed.