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.

A procedure to determine the individually comfortable position of visual displays relative to the eyes.

In an intervention phase, 38 operators used four different imposed screen positions (near versus distant, high versus low) for a full working day to experience the advantages and disadvantages. Screens at about 66 cm induced more reported strain than screens at about 98 cm. When operators later freely selected their individually most comfortable screen position, individually different changes due to the intervention were observed: some subjects changed to shorter, others to longer viewing distances, some operators adjusted the screen lower, others higher. These effects were confirmed in repeated tests. Thus, trying out different screen positions appears useful for arranging the VDU workstation to the individually most comfortable screen location relative to the eyes.

Preferred position of visual displays relative to the eyes: a field study of visual strain and individual differences.

At office workplaces equipped with visual display units (VDU) that were adjustable to various positions relative to the eyes short and long viewing distances from the eyes to the screen were imposed (mean value of about 63 and 92 cm) at two levels of screen height so that the visual target was either at eye level or 18 cm below, on the average. The change from far to near viewing distance produced a larger increase in eyestrain when the VDUs were at eye level. High screens resulted in greater eyestrain than low screens, as shown by correlations over subjects. When operators were free to adjust the most comfortable screen position, the group of 22 participants preferred viewing distances between 60 and 100 cm and vertical inclination of gaze direction between horizontal and -16 degrees downwards. However, within most subjects the range of preferred screen positions was much smaller. Between 3 days during a 1-month period the test-retest correlations of the preferred screen positions were highly significant, both for viewing distance and vertical gaze inclination. When operators were forced to work at a shorter distance than their preferred viewing distance they reported more visual strain. Thus, operators appear to prefer an individual adjustment of the screen relative to the eyes in order to avoid visual strain and discomfort at VDU work.

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.

[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.

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.

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.

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.

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.

[The effect of an on the job training program -- stairclimbing -- on the physical working capacity of employees (author's transl)]. / Uber den Einfluss einer berufsnahen Trainingsmöglichkeit auf die körperliche Leistungsfähigkeit von Angestellten.

Following medical screening and physical fitness testing (W170) 52 voltuntary employees in a 31-story administration building were formed into matched pairs and randomly allocated into intervention (stairclimbing) and control (lift) groups. The intervention group was asked to climb at least 25 floors/workday or 125 floors/week. the control group was asked to use only the lift. The intervention time was 10 weeks. The physiological measurements were made before and after the intervention. The number of stairs climbed was recorded daily in a diary. The heart rate was recorded continuously over one workday before and during the interventions. The average quantity of training in the final intervention group (n = 19) was 29.9 floors/workday or 36,790 kpm/week and in the control group 4.6 and 5980 correspondingly. The average training frequency was 4.3 in intervention and 1.4 climbs/workday in the control group. The average number of continuous floors used during climbing was 7.0 in intervention and 3.4 in control group. The average number of minutes on heart rate level of 130-159 beats/min during one workday was 7.8 in intervention and 1.6 in control group. The W170 (W/kg) increased 17.8% and the predicted VO2max (ml/min/kg) 15.1% in intervention group. The difference between the intervention group and the control group was significant (p less than 0.01). It was concluded, that stairclimbing is a suitable on the job physical activity program for middle-aged, untrained men.

[Study of the circadian variation of different circulatory and respiratory functions at submaximal and maximal ergometer work (author's transl)]. / Untersuchung zur Tagesperiodik verschiedener Kreislauf-und Atemgrössen bei submaximalen und maximalen Leistungen am Fahrradergometer

The maximal aerobic power of six highly trained young cyclist, mean age 16.3 years and mean VO2max 4.9 l/min, was directly measured at intervals of 4 hrs. A Latin square design was used for the test order. At submaximal work of O2-consumption 2.4 to 4.4 l/min no circadian variation of any single function was found. However, at maximal work load the differences between the maxima and minima values were 12.4% for maximal work output (W max), 7.8% for expiratory minute volume (V Emax), 5.7% for maximal aerobic power (VO2max) and 3.4% for maximal heart rate (H Rmax). All the functions--with the exception of VO2max-had their minima at 0300 hrs; the minima of VO2max was reached already at 2300 hours. The maxima-values of V Emax and VO2max were measured at 1500 hrs, of W max and H Rmax at 0700 and of H Rrest at 1900 hrs correspondingly. A one-tailed test showed significant differences between the maxima and minima values of all variables (P less than 0.05). The results suggest a decreased cardiopulmonary working capacity at night. However, this impairment is only of practical importance if the work will be done near the limit of endurance capacity. Besides it will suggest, that the indirect methods for assessing the cardiopulmonary capacity based on VO2max and W170 are not useful at nighttime, because the presuppositions for these methods are limited of the time of day.