PubMed Health⌕ Search

Biomedical subjects

J Winkel

Publications and source records attributed to J Winkel.

At least 37 records · Page 2Linked to original sources
PubMed1994

Evaluation of two instruments for recording sitting and standing postures and number of foot steps.

The study evaluates two simple instruments that may be used to describe aspects of physical workload in almost any occupation: a pedometer, which measures the number of steps taken by the subject wearing it, and a posimeter, which quantifies the time spent sitting and the number of changes between sitting and a The present data showed that the pedometer registers the correct number of steps at 'ordinary' walking speed independent of type of floor (plastic carpet and stone floor), shoes (wooden shoes and sneakers) and gender. At 'slow' walking (2.4 km/h) a reduced number of steps was recorded. In a field study the median difference between pedometer registration and observation was 6% (range 1-27) of the observed obtained for the five investigated pedometers was 0-15%. The posimeter was found to give a good estimate of the percentage time spent sitting (mean deviation 3%, range 0-15%). The number of changes between sitting and standing was overestimated by the posimeter (median deviation 63% of the observed). Some extreme working postures can be misread by the posimeter.

Journal Article↗
PubMed1994

Direct measurements and systematic observations of physical workload among medical secretaries, furniture removers and male and female reference populations.

The aim of this investigation was to collect quantitative information about the occurrence of manual materials handling and working postures in working life. Direct technical recordings and systematic observations by trained ergonomists were used throughout a whole working day on 12 male furniture removers, 13 female medical secretaries, 27 males and 45 females randomly sampled from the working population in the Stockholm area. A quantitative job exposure profile was obtained by weighting together exposure data obtained by observation of tasks occurring during a normal working week. The results showed no major differences in physical exposures between the male and female reference populations. The medical secretaries spent less time than the female population kneeling/squatting and longer time than any other group with repetitive hand movements. Exposure data for task and job should be clearly distinguished.

Journal Article↗
PubMed1994

Assessment of physical work load in epidemiologic studies: concepts, issues and operational considerations.

Ergonomic epidemiology is a rapidly increasing field of research providing data on the occurrence of musculoskeletal disorders and possible risk factors. The present paper states, on the basis of a literature overview, that physical work load (mechanical exposure) is poorly defined and measured in most studies on ergonomic epidemiology. On this background the paper: (1) suggests adjustments of mechanical exposure concepts and terminology; (2) concludes that invalid exposure assessment may, to a large extent, explain the lack of quantitative data on relationships between mechanical exposures and musculoskeletal disorders; and (3) suggests some guidelines for future quantitative assessments of mechanical exposure in large populations.

Epidemiologic Methods↗
PubMed1993

Validity of self-reported exposures to work postures and manual materials handling. Stockholm MUSIC I Study Group.

Exposure data from self-administered questionnaires on manual materials handling and work postures were validated in relation to direct measurements and systematic observations on 39 men and 58 women representing 45 different occupations. The agreement was tested at a dichotomous level and, when possible, with quantification of duration or frequency. At the dichotomous level the agreement was "acceptable" for nine variables concerning work postures and the handling of loads weighing > 5 kg. No variable showed "acceptable" agreement when the duration or the frequency was quantified in more detail (4- to 6-point scales). Musculoskeletal complaints seemed to introduce a differential bias for some lifting variables. Thus some variables for postures or the handling loads of > 5 kg may, under certain conditions, be acceptable for use in epidemiologic studies when the relative risks are high. However, self-reported exposure seems to be too crude if more-detailed information is required.

Female↗
PubMed1993

Biochemical indicators of hazardous shoulder-neck loads in light industry.

Prolonged, repetitive handling of light material is known to increase the risk of shoulder-neck disorders. Biological risk indicators related to musculoskeletal exposure, applicable by the general practitioner in the workplace, could provide an instrument for early intervention and rehabilitation. Eight women were studied, all full-time workers performing assembly tasks associated with a high prevalence of shoulder-neck complaints. All subjects were more tender in the shoulder region than young women in low-risk occupations. Heart rate recordings indicated a low general metabolic load during work. Concentrations in antecubital venous blood of several markers for metabolic stress and cellular damage (lactate, ammonia, hypoxanthine, urate, malondialdehyde, potassium, creatine kinase) were normal for all subjects, and showed no increase during 3 consecutive working days. Thus, the blood markers did not reflect hazardous shoulder-neck exposure.

Adult↗
PubMed1992

Can occupational guidelines for work-rest schedules be based on endurance time data?

Within the European Community, work is in progress to establish occupational guidelines for physical workload, including work-rest schedules. A model has been proposed which relies upon endurance time as a valid estimate of the short- and long-term physiological responses to continuous and intermittent exercise. On the basis of recent results from several Scandinavian research groups, the present paper questions the use of this model as a contribution to occupational guidelines. It is believed that the proposed model has a limited validity as a predictor of endurance time, as an indicator of short-term physiological responses, and as an estimator of risk for musculoskeletal disorders.

Adult↗
PubMed1991

Significance of skin temperature changes in surface electromyography.

Differing results have been reported concerning the direction and quantity of the electromyogram (EMG) amplitude response to changes in tissue temperature. The EMG signals from the soleus muscle of six healthy human subjects were therefore recorded during dynamic exercise (concentric contractions) at ambient temperatures of 30 degrees C and 14 degrees C. The mean skin temperature (Tsk) above the muscle investigated was 32.9 degrees C and 21.7 degrees C, respectively. The core temperature, estimated by rectal temperature, was unchanged. The cooling of the superficial tissues caused approximately a doubling of the EMG amplitude. For the probability level 0.9 in the amplitude probability distribution function, the average signal level increased from 73 microV to 135 microV (P = 0.02). The average mean power frequency of the EMG signal was reduced from 142 Hz to 83 Hz (P = 0.004). The amplitude increase was not due to shivering but other possible explanations are presented. As the changes in Tsk investigated were within the range which may occur normally during the working hours, it was concluded that Tsk should be carefully controlled in vocational EMG studies.

Adult↗
PubMed1991

Hand strength: the influence of grip span and grip type.

The maximal force from each of the fingers II-V (FF) and the resultant force between the jaws of the tool (RF), due to contribution from all fingers, were measured using a pair of modified pairs. The RF was measured at 21 handle separations and the FF was measured at seven handle separations for each finger. A traditional grip type was compared with a 'reversed' grip where the little finger was closest to the head of the tool. Sixteen subjects (8 females and 8 males) participated in the study. Both the RF and FF varied according to the distance between the handles. For both grip types, the highest RF was obtained at a handle separation of 50-60 mm for females and 55-65 mm for males. For wide handle separations, the RF was reduced by 10% (cm increase in handle separation). The force-producing ability of the hand was influenced by the grip type and the highest RF was obtained when using the traditional grip. An interaction was found between the fingers, i.e., the maximal force of one finger depended not only on its own grip span, but also on the grip spans of the other fingers. About 35% of the sex difference in hand strength was due to hand size differences.

Adult↗
PubMed1991

Quantifying variation in physical load using exposure-vs-time data.

Variation has in recent years become an important concept in the analysis of loads on the locomotor system in occupational life. Studies of controlled variation in isometric exercise have concentrated on the effects of introducing pauses at regular intervals into an otherwise constant load. A complete description of the cyclic character of such regimens requires a set of three parameters. We suggest the use of the set mean load/cycle time/duty cycle. The design of laboratory studies should more often be based upon the activity patterns found in occupational life. In studies observing exposure, the variation concept introduces problems concerning how to define and how to quantify 'variation'. It is shown that present methods (APDF analysis and contraction frequency analysis) individually fail to pick up important aspects of variation. A new method for exposure variation analysis (EVA) is proposed. Examples are presented of EVA performed on vocational EMG registrations.

Ergonomics↗
PubMed1990

Electromyographic activity in the shoulder-neck region according to arm position and glenohumeral torque.

The electromyographical (EMG) response to isometric ramp contractions of the right arm, the left arm, and both arms was studied using four pairs of surface electrodes above the right upper trapezius muscle (UT) of six men and six women. Contractions were made against gravity with the active arm(s) in eight positions, ranging from flexion to abduction. To describe arm positions, new, simple terminology was developed. Root mean square (rms)-converted EMG-signals were normalized (EMGnorm) with respect to a reference contraction. The EMGnorm corresponding to a 15 N.m torque in the right glenohumeral (GH) joint was strongly related to the position of the right arm (P less than 0.001). The shape of this relationship depended on the electrode position (P less than 0.001). The ratio between EMGnorm at 30 N.m and 15 N.m GH torques was related to arm position (P less than 0.001) and differed between electrodes (P less than 0.001). A left-side GH torque resulted in right-side (contralateral) EMG activity, typically corresponding to 20%-30% of that obtained during similar right-side GH torque. Bilateral GH torque implied 0%-50% increase in EMG activity as compared to that obtained with the right arm alone. The results have shown that signals from one pair of surface electrodes above UT cannot be taken as representative of the EMG activity from electrodes located elsewhere above UT. The EMG recordings reflected a complex pattern of muscular activation, significantly related to both outwardly visible factors (arm position, GH torque), and within-body servosystems (motor control reflexes).

Adult↗
PubMed1989

[Why do musculo-skeletal stress injuries increase?].

The innovation of technologies in the industrial countries in recent decades has involved increased physical monotony and inactivity in working life. Parallel to this development the ergonomic quality of work station design has been improved. But the corresponding reduction in physical stress does not seem to diminish the frequency of symptoms from the locomotor system. On the basis of studies carried out in recent years, a U-shaped relationship between physical stress and symptoms is suggested, i.e. frequency of symptoms may increase not only when the physical stress is high but also when it becomes very low. It is concluded that further research on acceptable physical stress should comprise studies aimed not only at upper but also at lower limits, including minimal variation of the physical load.

Bone Diseases↗
PubMed1988

Effects of leg activity and ambient barometric pressure on foot swelling and lower-limb skin temperature during 8 h of sitting.

Prolonged immobilization in an upright position often leads to discomfort and oedema in the feet of otherwise healthy subjects. To determine the significance of leg activity and ambient pressure on oedema formation, skin temperature (Tsk) and discomfort, 6 volunteers sat for 8 h with one leg immobilized and the other spontaneously active; one day at "sea level" (750 mmHg) and one day at reduced barometric pressure (540 mmHg). Foot swelling was measured by water plethysmography. Leg movements were continuously monitored by a Vitalog computer, and foot discomfort was estimated by analog-visual scales. The 8 hour swelling averaged 5.7% in the inactive foot, and 2.7% in the active foot (p less than 0.001). Tsk of the inactive foot levelled off towards ambient temperature (21 degrees C) within 4 h. For the active foot this fall was reduced by 2-3 degrees C (p less than 0.025). The increase in foot discomfort during the day was lowest in the active foot (p less than 0.005). High foot Tsk was associated with a high foot swelling rate. Reduced ambient barometric pressure had no effects on foot swelling or Tsk. It is concluded that modest leg activity during 8 h of sitting has several effects on the circulation in the feet: some effects promote and some prevent oedema formation. However, the net result is a reduction in foot swelling.

Adult↗
PubMed1988

An EMG-study of work methods and equipment in crane coupling as a basis for job redesign.

Previous studies have shown that physical strain is perceived as the main work environment problem for crane couplers. During one year, 70% of the crane couplers at two Swedish steelworks (n = 124) indicated complaints of the locomotor system. An experimental field study comprising seven healthy female crane couplers was therefore carried out to determine if crane coupling implies too high a physical strain for healthy individuals, and to suggest ergonomics solutions to such problems if they occur. The significance of using different methods and equipment for reducing physical strain was evaluated by vocational EMG (four shoulder/neck and arm muscles), heart rate and ratings of perceived exertion. The data suggest that crane coupling may have harmful effects on the shoulder/neck. The investigated changes in work methods and equipment reduced the peak loads. If the crane coupler also has to operate the crane by radio control, this implies a rationalisation as well as a reduction in strain.

Journal Article↗
PubMed1986

An evaluation of a tiltable office chair with respect to seat height, backrest position and task.

The amount of spontaneous movement during seated office work was estimated by analysing the tilting movements of a tiltable office chair. Both movement frequency and amplitude range were considered. The seat inclinations and subjective acceptability were also recorded. The seat was moved more frequently and with a greater range when adjusted 6 cm above popliteal level compared to 1 cm below, or when the backrest was pushed anteriorly or posteriorly compared to a middle position. The greatest acceptability occurred with the highest seat adjustment and the backrest in the middle position. Typing or desk-work influenced movement to a similar extent.

Adult↗
PubMed1986

Swelling of the foot, its vascular volume and systemic hemoconcentration during long-term constrained sitting.

Swelling of the left foot and changes in its vascular volume (VV) were studied in seven healthy subjects during 8 h of seated work without leg movements. Changes in total plasma volume (PV) were calculated from hematocrit values. Reference values (r.v.) were obtained during a working day requiring intermittent physical activity (walking). Significant changes during the first 4 h: the foot swelled by 3.5% (r.v.: 2.2%) and VV was reduced by 0.5% of the foot volume (r.v.: increased by 0.3%). Accordingly, the interstitial fluid volume (IFV) of the foot increased by 4.0% (r.v.: 1.9%). The loss of PV was 6.3%. During the last 4 h the only significant change was an increase in foot volume by 1.9%. It is concluded that (1) foot swelling should be corrected for changes in VV to obtain an exact measure of the change in IFV, (2) prolonged elevated pressure, assumed to occur in the feet during relaxed sitting, does not imply distension ("delayed compliance") of the vascular system as previously suggested, (3) hemoconcentration seems to reach complete stability during the initial period of quiet sitting, (4) loss of PV during sedentary work may be avoided by a modest increase in leg activity.

Blood Volume↗
PubMed1986

Muscular performance during seated work elevated by two different EMG methods.

As part of a larger ergonomic survey of seated work, the myoelectric activity of soleus and erector spinae was studied during typing and desk work while sitting on three different office chairs. Muscular performance was evaluated by two EMG methods: (1) the frequently used analysis of the amplitude probability distribution function (APDF) of the EMG signals, and (2) a recently presented method which considers muscular contraction frequencies according to the load levels. The latter indicated significant differences in contraction frequencies which did not appear from the APDF. Moreover, the APDF illustrated differences in load levels which were not evident from the frequency analyses. It is suggested that both EMG methods should be used in evaluations of muscular activity.

Adult↗