Search PubMed⌕ Search

Biomedical subjects

M Hagberg

Publications and source records attributed to M Hagberg.

At least 73 records · Page 4Linked to original sources
PubMed1992

Radiographic osteoarthrosis in the acromioclavicular joint resulting from manual work or exposure to vibration.

The hypothesis that manual work and exposure to vibration are antecedents to the development of osteoarthrosis was assessed employing a cross sectional study design. The frequency of osteoarthrosis in the acromioclavicular joint was studied in three groups of workers in the construction industry. Two groups were manual workers (54 bricklayers and 55 rock blasters); the third group consisted of 98 foremen. The radiographic appearance of the right and left acromioclavicular joints was classified into one of five grades of osteoarthrosis. A protocol was developed to assess exposure on the basis of job title, years of manual work, total weight lifted during working life, and total hours of exposure to vibrating tools. Odds ratios for job titles (manual worker v foreman) and for years of manual work as indicators of exposure were of similar magnitude of around 2.5. Construction workers who had lifted more than 709 tonnes had an increased risk of developing severe osteoarthrosis of the right acromioclavicular joint, odds ratio: 2.62 (95% confidence interval (95% CI), 1.13-6.06). The odds ratio for the left side was 7.67 (95% CI, 2.76-21.34). In the analysis of vibration exposure, workers who had been highly exposed to vibration had an odds ratio of 1.99 (95% CI, 1.00-3.92) on the right side and 2.20 (95% CI, 1.07-4.56) on the left. This effect almost disappeared after simultaneous adjustment for manual work. Occupational and ergonomic factors, such as the sum of lifted tonnes during working life, job title, and the sum of years of manual work seem to be risk factors for osteoarthrosis of the acromioclavicular joint, whereas vibration alone was a weaker risk factor.

Acromioclavicular Joint↗
PubMed1992

Impact of occupations and job tasks on the prevalence of carpal tunnel syndrome.

In this investigation reported epidemiologic studies on carpal tunnel syndrome (CTS) (15 cross-sectional studies involving 32 occupational or exposure groups and six case-referent studies) were reviewed. The prevalence of CTS in the different occupational groups varied between 0.6 and 61%. The highest prevalence was noted for grinders, butchers, grocery store workers, frozen food factory workers, platers, and workers with high-force, high-repetitive manual movements. Odds ratios greater than 10 were reported for exposed groups in three studies. On the basis of epidemiologic and other evidence, it was concluded that exposure to physical work load factors, such as repetitive and forceful gripping, is probably a major risk factor for CTS in several types of worker populations. At least 50%, and as much as 90%, of all of the CTS cases in these exposed populations appeared to be attributable to physical work load.

Adult↗
PubMed1992

Electromyographic signs of shoulder muscle fatigue in repetitive arm work paced by the Methods-Time Measurement system.

Surface electromyographic (EMG) recordings from the lateral and cervical portions of the descending trapezius muscle and from the infraspinatus muscle were assessed for six female subjects performing a standardized repetitive work simulation task for 1 h. The work pace was determined according to the Methods-Time Measurement system to 2466 cycles.h-1. The variation in load levels were high and indicated dynamic muscle activity. A decrease in the EMG mean power frequency and an increase in the root-mean-square amplitudes, both indicating muscle fatigue, developed in all muscles of most of the subjects. EMG signs of fatigue, analyzed separately for each 5-min period, showed variable fatigue patterns both between muscles and between subjects. It is therefore suggested that dynamic work movements do not protect the muscles of the shoulder and neck from fatiguing processes in highly repetitive work with short cycle times.

Adult↗
PubMed1991

Human exposure to 3-carene by inhalation: toxicokinetics, effects on pulmonary function and occurrence of irritative and CNS symptoms.

Terpenes, especially 3-carene, may irritate the skin and mucous membranes and prolonged exposure may result in allergic contact dermatitis or chronic lung function impairment. The toxicokinetics of 3-carene were studied in human volunteers exposed by inhalation (2 hr 50 W) in an exposure chamber on three occasions. The exposure concentrations were approximately 10, 225, and 450 mg/m3 3-carene. The relative pulmonary uptake was high, approximately 70% for the higher exposure levels. Total uptake increased linearly with increasing exposure. The blood clearance of 3-carene observed in this study, 0.9 liter.kg-1.hr-1, indicates that 3-carene is fairly readily metabolized. About 3% of the total uptake was eliminated unchanged via the lungs while less than 0.001% was eliminated in the urine after the end of exposure. A long half time in blood was observed in the terminal phase which indicates a high affinity to adipose tissues. A statistically significant divergence between ratings of irritation during the high exposure level and during the medium and control levels was observed. The difference in airway resistance after exposure to a high concentration of 3-carene compared to control level was not significant (P = 0.02).

Administration, Inhalation↗
PubMed1991

Outcome of the abduction external rotation test among manual and office workers.

Reactions during the Abduction External Rotation (AER) test were studied among 71 platers and 70 assemblers exposed to vibratory tools and manual work and 45 unexposed white collar workers. The frequency of positive neurological reactions was 31% among the platers, 6% among the assemblers, and 16% among the white collar workers. Platers reported the highest fatigue rates in the shoulder regions during the test. A positive association was noted between a pathological AER test and current problems in the neck/scapula or shoulder/upper arm regions, day- or night-time numbness in the hands, tension neck, and carpal tunnel syndrome. Age, length of daily vibration exposure, and vibration acceleration level were also positively associated with a positive AER test outcome. The results indicate that the outcome of the AER test is sensitive to neck and shoulder disorders but also, to some extent, to the carpal tunnel syndrome.

Adult↗
PubMed1991

Percutaneous uptake and kinetics of methyl isobutyl ketone (MIBK) in the guinea-pig.

Continuous intravenous infusion of 0.478 mumol/min methyl isobutyl ketone (MIBK) was performed for 30 min in pentobarbital-anesthetized guinea-pigs. Epicutaneous exposure for 150 min was carried out 2.5 h later after administration of MIBK to a sealed glass ring on the clipped back of the animals. Arterial blood was analyzed for MIBK by gas chromatography. Blood clearance averaged 201 ml.min-1.kg-1 body wt. A maximum percutaneous uptake of 1.1 mumol.min-1.cm-2 was reached 10-45 min after the onset of exposure and decreased to 0.56 mumol.min-1.cm-2 during the latter part of exposure.

Administration, Cutaneous↗
PubMed1991

Recovery from symptoms after carpal tunnel syndrome surgery in males in relation to vibration exposure.

A follow-up study was conducted in forty-one men (fifty-five hands) treated surgically for carpal tunnel syndrome. The number of hours of vibration exposure and exactly which hand tool was used were recorded and each tool was categorized according to vibration level. The patients were divided into a low exposure and a high exposure group. Age at surgery, mean distal latency in the median nerve, and the duration between onset of symptoms and surgery were similar for the two groups. Only one patient experienced nocturnal paresthesia at follow-up in the low exposure group in contrast to twelve in the high exposure group. This corresponded to an age-standardized odds ratio (relative risk) of eighteen for nocturnal paresthesia after surgery in the high exposure group, with the low exposure group as referents. Previous vibration exposure may influence the recovery after carpal tunnel surgery.

Adult↗
PubMed1991

Changes in muscle morphology in chronic trapezius myalgia.

Muscle biopsies of the descending portion of the trapezius muscle from female patients with chronic trapezius myalgia and from healthy women were analyzed with enzyme histochemical and immunohistochemical methods. Frequency, area, and capillarization of the muscle fiber types were determined. A biochemical analysis determined the lactate concentration of mixed muscle samples and the adenosine triphosphate (ATP) and phosphocreatine levels in single muscle fibers. The patients had larger type I fibers and a lower capillary:fiber area ratio for type I and type IIA fibers. The patients also exhibited lower levels of ATP and phosphocreatine in both type I and type II fibers. It is suggested that there might have been an imbalance between the capillary supply and the cross-sectional fiber area of type I and type IIA fibers in the patients. This imbalance might be of significance in the development of muscular fatigue and pain.

Adult↗
PubMed1990

Exposure to methyl isobutyl ketone: toxicokinetics and occurrence of irritative and CNS symptoms in man.

The toxicokinetics as well as irritative effects and CNS symptoms of methyl isobutyl ketone (MIBK) were studied in human volunteers during inhalation exposure. The volunteers were exposed (2h, 50 W) in an exposure chamber on four different occasions to about 10, 100 and 200 mg/m3 MIBK and to a combination of about 100 mg/m3 MIBK and 150 mg/m3 toluene. The relative pulmonary uptake of MIBK was about 60% and the total uptake increased linearly with increasing exposure concentration. The concentration of MIBK in blood rose rapidly after the onset of exposure and no plateau level was reached during exposure. No tendency for saturation kinetics could be observed within the dose interval and the apparent blood clearance was 1.61/h/kg at all exposure levels. The concentration of unchanged MIBK in the urine after exposure was proportional with the total uptake. Only 0.04% of the total MIBK dose was eliminated unchanged via the kidneys within 3 h post exposure. The concentrations of the metabolites 4-hydroxy-4-methyl-2-pentanone and 4-methyl-2-pentanol were below the detection limit (5 nmol/l). Irritative and CNS symptoms occurred during exposure. The degree of both irritative and CNS symptoms increased during exposure to 100 and 200 mg/m3 compared with 10 mg/m3, but combination exposure with toluene exhibited the most pronounced effect. There were no significant effects from exposure on the performance of a simple reaction time task or a test of mental arithmetic.

Administration, Inhalation↗
PubMed1990

Perception of cutaneous electrical stimulation in patients with craniomandibular disorders.

Perception thresholds for stimulation, discomfort, and pain were measured with electrical stimulation over the masseter area. Patients with chronic symptoms and signs of craniomandibular disorders reported significantly higher thresholds of all three variables compared with healthy controls. There were significantly negative correlations between the patients' pre-experimental discomfort and pain ratings on the Borg's scale and perception thresholds measured for discomfort and pain. The patients who presented the highest pain ratings in masticatory muscles and/or joints had the lowest threshold values when reporting discomfort and pain during gradually increased current intensity. This could be due to the cognitive effects of pain.

Adult↗
PubMed1989

Risk assessment of vibration exposure and white fingers among platers.

The dose-response relationship between vibration exposure and vascular disorders in the hands was examined in platers. The study was based on a cross section of 89 platers and 61 office workers divided according to exposure to vibration into four groups. Vibration exposure was assessed by measuring the acceleration intensity on a sample of tools, together with both subjective rating and objective measurements of the exposure time. The frequency-weighted energy equivalent acceleration for 4 h was 4.6-4.7 m/s2. The point prevalence of white fingers was 42% for the plater category currently exposed with an odds ratio of 85. The time laps before contraction of white fingers (latency time) was four years for the 10th percentile, and was shorter than predicted according to the ISO-5349 standard. The prevalence of white finger symptoms staged according to the Taylor-Pelmear scale was comparable to the prevalences according to the Stockholm Workshop Scale. Vibration exposure was the dominant source of white fingers and each year of vibration exposure increased the odds ratio for white fingers by 11%. Distal circulation in the hands was assessed by a timed Allen test. The odds ratio for a positive Allen test was higher for the workers exposed to vibration compared to the non-exposed workers. The use of the timed Allen test is suggested in the clinical examination for vibration white fingers. The observed high risk for contracting white fingers could be prevented by exposure level reduction and/or restriction of exposure duration.

Adult↗
PubMed1989

Surface EMG amplitude and frequency dependence on exerted force for the upper trapezius muscle: a comparison between right and left sides.

Surface electromyographic (EMG) amplitude and mean power frequency (MPF) were used to study the isometric muscular activity of the right versus the left upper trapezius muscles in 14 healthy right-handed women. The EMG activity was recorded simultaneously with force signals during a 10-15 s gradually increasing exertion of force, up to maximal force. Only one side at a time was tested. On both sides there was a significant increase in EMG amplitude (microV) during the gradually increasing force from 0% to 100% maximal voluntary contraction (MVC). The right trapezius muscle showed significantly less steep slopes for regression of EMG amplitude versus force at low force levels (0%-40% MVC) compared intra-individually with high force levels (60%-100% MVC). This was not found for the left trapezius muscle. At 40% MVC a significantly lower MPF value was found for the right trapezius muscle intra-individually compared with the left. An increase in MPF between 5% and 40% MVC was statistically significant when both sides were included in the test. The differences in EMG activity between the two sides at low force levels could be due to more slow-twitch (type I fibres) motor unit activity in the right trapezius muscles. It is suggested that this is related to right-handed activity.

Adult↗
PubMed1989

Evaluation of two floor-mopping work methods by measurement of load.

The workload for two different methods of floor mopping in 11 healthy female cleaners was evaluated by rating the perceived exertion, by recording the ECG and EMG and by video analysis of postures and movements. There was less perceived exertion and local muscle loading during work when the 'push' method was used than with the 'figure-of-eight' method. The 'push' method nevertheless still implied a level of static loading that may be harmful during long term work. The methods did not differ regarding measured heart rate and oxygen consumption. However, for two cleaners the 'figure-of-eight' method and for three cleaners the 'push' method implied a work load corresponding to more than 40% of their normal oxygen uptake. Large individual variations in work postures and movements were found for both methods.

Adult↗
PubMed1989

The effects of different pause types on neck and shoulder EMG activity during VDU work.

Surface electromyographic recordings on the right side from the descending part of the trapezius muscle and from the levator scapulae muscle and discomfort ratings were assessed for twelve female word processor operators. The operators were studied during three work periods of 30 min each. Three different kinds of pauses, active pauses with pause gymnastic movements, passive pauses with rest and diverting pauses, were introduced into the work every six minutes. The static muscular load was low and about the same for the three work periods. High contraction levels with a duration of at least 1% of the registration time differed significantly between the three types of pauses, reflecting the activity during the pauses itself. Active pauses could thus change the muscle activity pattern. There was a tendency to prefer pauses with activity to passive pauses.

Adult↗