Back muscle activation pattern and spectrum in defined load situations.

For the prevention and rehabilitation of low back pain the understanding muscle function in the low back region is essential. Important aspects of function include the muscle activation patterns and muscle fatigue. In the low back region m. erector spinae plays a critical role. The different parts of this muscle complex differ considerably in function. Following the concept of Bergmark [A. Bergmark, Stability of the lumbar spine, Acta Orthop. Scand. 60 (1989) 1-54] trunk muscles can be divided in two subsystems, the global-mobilizing-system and the local-stabilizing-system. At present the multifidus muscles are assigned to the local whereas the longissimus and iliocostalis muscles are assigned to the global system. From results of the four parts of our investigation, it can be shown that essential information about muscle function can be obtained by spectral and intra- as well as inter-muscular surface EMG parameters. Obtained data demonstrated functional transitions between the local and global system of trunk muscles for the multifidus muscle.

Additive impairment of the barrier function and irritation by biogenic amines and sodium lauryl sulphate: a controlled in vivo tandem irritation study.

Biogenic amines are potential irritants e.g. in fish-, meat-, milk- and egg-processing professions like cooks, butchers and bakers. The aim of this study was to test the irritative and barrier-disrupting properties of the biogenic amines ammonium hydroxide (AM), dimethylamine (DMA) and trimethylamine (TMA). A repeated sequential irritation of 30 min twice per day was performed over a total of 4 days (tandem repeated irritation test) on the back of 20 healthy volunteers of both sexes with AM, DMA, TMA and sodium lauryl sulphate (SLS). The epidermal barrier function was assessed with a Tewameter TM 210, stratum corneum surface pH was measured with a Skin-pH-Meter 900, inflammation was assessed with a Chromameter CR-300 on the a* axis for redness and a visual score was recorded. All tested biogenic amines (AM, DMA and TMA) induced a barrier disruption and a pH increase paralleled with a 1-day-delayed onset of inflammatory signs. These effects were further enhanced and accelerated by a sequential application of SLS together with the biogenic amines, and inflammation occurred earlier than with the single compounds. Acetic acid (AA) in contrast did only show mild barrier disruption and no significant inflammatory signs. Our system allowed a ranking of the different compounds in their irritative potential in the tandem irritation with SLS: SLS > NaOH > TMA > AA > AM > DMA. The results are suggestive that in the food-processing industry the simultaneous contact with biogenic amines and harmful detergents like SLS should be minimized.

Additive impairment of the barrier function by mechanical irritation, occlusion and sodium lauryl sulphate in vivo.

BACKGROUND: The interaction between potential irritants in the workplace might be important because workers are not usually exposed to a single irritant, but to multiple potentially harmful substances. Physical irritant contact dermatitis caused by friction or mechanical abrasion is a common occupational dermatosis. Prolonged water exposure by occlusion is also common in the workplace. Several studies have revealed the negative effect of the common anionic detergent sodium lauryl sulphate (SLS) on permeability barrier function. OBJECTIVES: To study the additive impairment of permeability barrier function by mechanical irritation combined with 0.5% SLS or prolonged water exposure by occlusion, as models of mild irritation. METHODS: The volar forearms of 20 healthy volunteers were exposed to mechanical irritation and occlusion with water or 0.5% SLS for four consecutive days in a combined tandem repeated irritation test (TRIT). Permeability barrier function was measured with a Tewameter TM 210. Irritation was assessed with a Chromameter CR 300 and a visual score. RESULTS: Barrier disruption in our model was rated as follows: occlusion with SLS and mechanical irritation > occlusion with SLS > occlusion with water and mechanical irritation > mechanical irritation and occlusion with water > occlusion with a glove and mechanical irritation > mechanical irritation > occlusion with water. Barrier disruption caused by occlusion or mechanical irritation was enhanced by the tandem application. The choice of irritant under occlusion, time of occlusion and order of tandem application all affected the degree of barrier disruption. Evaporimetry was able to detect early stages in the development of an irritant reaction before it became visible. Chromametry was not able to detect this early response. CONCLUSIONS: Physical irritants (friction, abrasive grains, occlusion) and detergents such as SLS represent a significant irritation risk and should be minimized, especially when acting together, as shown in our TRIT model.

Air flow at different temperatures increases sodium lauryl sulphate-induced barrier disruption and irritation in vivo.

BACKGROUND: Combined exposure to dry climatic conditions and local heat sources together with detergents represents a common workplace situation. These conditions may support the induction of chronic barrier disruption leading subsequently to irritant contact dermatitis (ICD). OBJECTIVES: To test the irritant and barrier disrupting properties of air flow at different temperatures and velocities. METHODS: Using noninvasive biophysical measurements such as transepidermal water loss (TEWL) (TM 210; Courage & Khazaka, Cologne, Germany) we assessed the effects of short-term exposure to air flow at different temperatures (24 degrees C and 43 degrees C) in combination with sodium lauryl sulphate (SLS) 0.5% on the skin of 20 healthy volunteers in a tandem repeated irritation test. Chromametry was used to control the accuracy of the SLS irritation model. RESULTS: In our study air flow alone did not lead to a significant increase in TEWL values. Sequential treatment with air flow and SLS led to an impairment of barrier function and irritation stronger than that produced by SLS alone. The two different air flow temperatures led to different skin temperatures but had no influence on permeability barrier function. CONCLUSIONS: Warm air flow has an additional effect on the SLS-induced barrier disruption in a tandem irritation test with sequential exposure to SLS/air flow. This combination is suspected to promote ICD in workplace and household situations, especially in short-term applications as tested in our model.

Sequential application of cold and sodium lauryl sulphate decreases irritation and barrier disruption in vivo in humans.

BACKGROUND: Irritant contact dermatitis (ICD) is one of the most frequent types of occupational dermatitis. Different factors are involved in the development of contact dermatitis. In the food-processing industry, the combined exposure to different irritants may be involved in the development of ICD. Few data have been published regarding the irritant potential of sodium lauryl sulphate (SLS) in combination with cold. OBJECTIVES: The present study was intended to analyse whether cold exposure and low skin temperature influence the development of ICD. METHODS: Twenty (part I) and 12 (part II) healthy volunteers were exposed twice daily for 4 days to SLS alone, different low temperatures alone (4 degrees C six times for 90 s with an interval of 20 s or 15 degrees C for 10 min) or a combination of cold and SLS (19.6 microL SLS 1% cm(-2), part I; or 52.6 microL SLS 0.5% cm(-2), part II) using the tandem repetitive irritation test. Irritant cutaneous reactions were measured by noninvasive biophysical methods with transepidermal water loss as a parameter for permeability barrier function and skin colour reflectance together with visual scoring as parameters for inflammatory reactions. RESULTS: Cold alone caused no significant skin reaction compared with untreated control. Exposure to SLS alone and SLS together with cold (independent of the applied temperature of 4 or 15 degrees C) twice daily induced a clear irritant reaction and barrier disturbance. Reactions did not differ whether SLS was applied before or after cold. Furthermore, 'tandem application' of cold and SLS diminished the barrier disruption and irritant reaction compared with SLS alone. CONCLUSIONS: We conclude that the application of cold may have a protective effect on the development of ICD, at least in our short-term model.

[The skin prick test and nasal provocation test with individually prepared flour extracts in patients with bakers' rhinitis and asthma]. / Prick-Test und nasaler Provokationstest mit individuellen Mehlextrakten bei Bäckerrhinitis.

The reliability of skin prick tests (SPT) may be insufficient for the screening of occupational inhalant allergies. The influence of different flour extracts on the SPT in flour allergic subjects has not been compared previously. In this study, SPT reactions against two commercially available rye and wheat flour extracts and individually prepared extracts from flour samples were compared in 35 patients with known bakers' rhinitis. Flour sensitization was confirmed by a positive nasal provocation test (NPT) and/or serum-specific IgE. The sensitivity of NPT with a combination of rye and wheat flour extracts of individual flour samples was 94%. Wheat and/or rye flour specific IgE (RAST>/=2) was true positive in 86%. The sensitivity of the SPT was 94% for individual rye flour extracts compared to 38% and 59% for two commercially available rye flour extracts and 88% for individual wheat flour extract compared to 53% and 48% for commercially available wheat flour extracts. SPT and sIgE did not reveal a significant difference in prevalence between rye and wheat flour sensitization. Thirty healthy volunteers served as the control group. Three control subjects with histamine equivalent SPT reactions to grass pollen had a positive SPT reaction against individual flour extracts, whereas NPT with undiluted individual flour extracts was negative in all controls. SPT with individually prepared flour extracts appears to be sensitive for the demonstration of inhalant flour allergy. Our findings show that extracts of individual flour samples rather than commercially available extracts should be used for both SPT and NPT if flour allergy is suspected.

Surface EMG of shoulder and back muscles and posture analysis in secretaries typing at visual display units.

OBJECTIVE: A study was carried out to investigate temporal changes of activation of shoulder and back muscles in workers at visual display units by means of surface EMG. Moreover, postural parameters were recorded to distinguish fatigue-related from posture-related changes of the myoelectrical activity. METHODS: Nine healthy female office workers typed texts spoken from tape during three 1-h-long sessions. After the first and again after the second hour there was a break of 15 min. Sixteen-channel surface EMG was bipolarly recorded from the erector spinae, trapezius, deltoid and sternocleidomastoid muscles. Root mean square (RMS) and power spectrum median frequency of the EMG were calculated. Sitting posture was assessed using an eight-channel movement analysis system with ultrasound markers. The position of the seventh cervical spinous process and the left and the right acromion were analysed synchronously with the EMG characteristics using regression analysis. RESULTS: The normalised RMS of the left and right trapezius muscle increased, while the median frequency did not change. The increase of the normalised RMS was significantly lower when the linear influence of posture was excluded. On average, the distance between C7 and the left and right acromion decreased within each working an hour. C7 became lower on average by 5.5 mm within an hour, whereas the acromions became lower by only 1.7 mm (left) and 3.3 mm (right). CONCLUSION: The increase in trapezius muscle activity was partly related to a lifting of the shoulders to compensate a slight slumping of the back. Another part of the EMG activity increase has to be attributed to fatigue, to attention-related activity or to the combination of both. Therefore, training of the back muscles and a varied organisation of work might have a preventive effect with respect to musculoskeletal complaints in VDU workers.

Development of occupational skin diseases during vocational training in baker and confectioner apprentices: a follow-up study.

Baker and confectioner apprentices have been included in a prospective follow-up study in the region of East Thuringia, to evaluate risk factors for the development of hand dermatitis. Starting in August 1996, the apprentices have been interviewed and examined in a standardized way right at the beginning (n=91) of their vocational training, 6 (n=79) and 12 months (n=63) later. To gain objective data, TEWL score was also assessed at 3 standardized sites on the hands. In their case histories, 3.3% (n=3) of the apprentices reported hand dermatitis. The 1st assessment after 2 to 4 weeks vocational training revealed hand eczema in 17.5% (n=16) of the individuals. At the follow-up after 6 months of training 29.1% (n=23), and after 12 month of training 27.0% (n=17), of the apprentices had hand dermatitis of mild to moderate severity. Within 6 months, the TEWL score rose significantly (p<0.001) from 11.9 g m(-2) h(-1) (-/+5.4) to 16.8 g m(-2) h(-1) (-/+9.5). After 12 months, the TEWL score was 14.9 g m(-2) h(-1) (-/+4.6). For the atopic skin diathesis (>10 points of Diepgen's atopy score), there was a significant tendency to be a predictive factor for the development of occupational hand dermatitis. TEWL score failed to correlate with the development of skin damage in our study. The same was true for respiratory atopy and metal sensitization.

[Effectiveness of secondary preventive programs for patients with asthma and rhinitis in the baking industry]. / Effektivität eines Sekundär-Präventionsprogramms für asthmatisch und rhinitisch Erkrankte im Bäckerhandwerk.

Since 1992 the German industrial professional association for the food industry and gastronomy (Berufsgenossenschaft Nahrungsmittel und Gaststätten), which is responsible for statutory accident insurance has been offering a specific patient education programme to bakers suffering from occupationally induced obstructive pulmonary disease or allergic rhino-conjunctivitis, who do not quit their jobs and wish to continue working as bakers. The programme aims at preventing aggravation of the disease 74 male bakers with a mean duration of illness of 10 years on entering the programme were examined between 1 and 5 years (mean: 2.9) after participating in the patient education seminar. For a subpopulation of 55 of these patients spirometric measurements were available for the time before programme entry and at follow-up. Data on time spent at the bakehouse, prevalence of symptoms, frequency of symptoms at the site of working and during leisure hours, sleep disturbances and emergency situations were collected at the follow-up examination both for the time before programme entry and at follow-up, respectively. Direct ratings of the amount of changes in distress caused by the disease and of the quality of life were also obtained. The prevalence of 8 of the 9 most frequently reported symptoms decreased significantly, e.g. dysponoea from 70% to 42% and fear of suffocation from 30% to 3%. Participants reported on highly significant reductions in the frequency of disease-specific complaints during work and outside the working place, sleep disturbances and situations requiring immediate medical intervention. Between 64% and 85% of the patients experienced improvement of distress, physical and work performance, private and family life, and ability for self-management. Lung function did not deteriorate: mean FEV1 was 88% (+/- 23) at first and 90% (+/- 19) at second measurement. These results could not be explained by changes in medication. It is concluded that the programme is effective in reducing symptoms and distress and in improving quality of life in bakers with occupational respiratory disease who voluntarily continue to work as bakers.

[Contractile reserve as a new parameter for determining the performance of the heart muscle using a noninvasive measuring method]. / Kontraktile Reserve als neuer Parameter zur Bestimmung der Leistungsfähigkeit des Herzmuskels mit Hilfe eines nichtinvasiven Messverfahrens.

Chronic cardiac insufficiency is an illness with increasing epidemiological importance and mortality. Therefore different invasive and non-invasive investigation methods for early recording were developed. The left ventricular ejection fraction (LVEF) has played a special role in this direction. The determination of the contractile reserve by means of non-invasive measurement of blood pressure and flow through the aortic valve is a new and up to now widely unknown method for recording the capability and power reserve of the of myocardium. Since no comparative investigations are known from literature and results from a follow-up are not available yet, we tested whether, by means of contractile reserve, the discrimination of subjects with different cardiac power is possible or not. Forty-two men between 44 and 62 years of age belonging to three groups with different cardiac power (persistence trained, healthy subjects and patients with CHD) were examined non-invasively. The main result of the study is that it is possible to distinguish between the three groups significantly by means of the contractile reserve. The largest value (15.25 W +/- 3.46 W) was found in the "persistence trained" group, followed by the "healthy subjects" (10.85 W +/- 4.19 W). The smallest values were from the "patients" group (7.88 W +/- 2.95 W). The differences between the mean values of the CHD "patients" and the "persistence trained" were significant (p < 0.001). Similar comparisons of the groups of "healthy subjects" and "trained persons" and "healthy subjects" and "patients", respectively, yield p values of p = 0.007 and p = 0.040. These differences are also significant. This study is a first investigation and description of the method. A validation only can be achieved by follow-up investigations.

Natural vegetable fats in the prevention of irritant contact dermatitis.

Chronic irritant contact dermatitis (ICD) is one of the most pressing problems in occupational medicine and is common in the food processing industry. To date, protective creams that fulfil the special requirements in the foodstuffs industry have not been available. Therefore, we studied the efficacy of pre-exposure application of natural vegetable fats in the prevention of experimentally induced ICD. A panel of 20 healthy volunteers was tested with a repetitive irritation test using sodium lauryl sulfate (SLS) as a standard irritant in a randomized study. Application sites were assessed clinically and by the use of bioengineering techniques (evaporimetry, chromametry, and corneometry). Rape seed and palm fats showed significant protective potential. Gas-chromatographic analysis revealed differences in the fatty acid composition of the vegetable. Higher content of linoleic acid and lower content of oleic acid was associated with beneficial effects. Our results are a new approach in the prevention of ICD and towards the development of new protective preparations for workplaces in the foodstuffs industry.

Fruit acids and sodium hydroxide in the food industry and their combined effect with sodium lauryl sulphate: controlled in vivo tandem irritation study.

BACKGROUND: Cutaneous exposure to a variety of irritants has been extensively studied in recent years. Nevertheless, knowledge of the induction of irritant dermatitis, especially by mild irritants at low doses and for a short duration of exposure, is still incomplete. OBJECTIVES: To quantify the irritant effects and barrier disruption properties of ascorbic acid (ASC), acetic acid (ACA) and sodium hydroxide (NaOH), particularly in combination with an anionic detergent, sodium lauryl sulphate (SLS). METHODS: In a tandem repeated irritation test, the irritants were applied for 30 min twice daily for 4 days to the skin of the mid-back of 19 healthy volunteers of both sexes. We used bioengineering techniques for measurement of transepidermal water loss (TEWL) and skin colour reflectance, as well as visual scoring. RESULTS: Repeated application of ASC and ACA caused a moderate increase in TEWL and erythema. The sequential application of ASC or ACA and SLS enhanced these effects. NaOH induced a strong reaction when applied both occlusively and nonocclusively as well as in combination with SLS, with an early onset of the inflammatory signs, leading to discontinuation of the application on the third day in most of the test fields. Notably, the irritant effect of NaOH was not as marked when applied sequentially with SLS. CONCLUSIONS: Our results demonstrate that concurrent application of an anionic detergent and a mild acidic irritant can lead to disruption of the barrier function which, although not additive, is still considerable. The combined application of SLS and mild acids does not prevent SLS-induced irritation. Furthermore, we showed that NaOH in low concentrations may also act as a potent irritant but that its effect is not enhanced by SLS. The necessity of adequate skin protection and reduction of contact with substances that are potentially barrier disruptive and irritant, e.g. in the food industry, is emphasized, not only when handling detergents, but also when processing food products.