Veerle Hermans

Lipoatrophia semicircularis and the relation with office work

The relation between lipoatrophia semicircularis (LS--band-like circular depressions and isolated atrophy of the subcutaneous fatty tissue on the anterior thighs and sitting posture or pressure on the seat surface of office chairs was investigated in an office environment. A questionnaire was presented to 21 subjects and electromyographic measurements, video analysis and pressure measurements were performed. Remarkable posture differences between the LS group and the group without LS were found: less use of the lumbar support of the chair, static sitting postures and a too high seat surface of the office chair were characteristics of the subjects with LS. These observations were confirmed by higher pressure measurements for the subjects with LS. In addition, highly significant pressure differences were found between different chairs.

Influence of electrode position on changes in electromyograph parameters of the upper trapezius muscle during submaximal sustained contractions

Abstract The purpose of the present study was to evaluate whether differences could be found in the changes in mean power frequency (MPF) and root-mean-square (rms) due to electrode positions on the upper trapezius muscle during a sustained submaximal task. A group of 25 healthy subjects performed a continuous forward flexion of the right arm at 20% of their maximal voluntary contraction (MVC). Three pairs of bipolar surface electrodes were positioned on a straight line between the spine of the seventh cervical vertebra (C7) and the lateral edge of the acromion. The fourth pair (the caudal position) was placed 2 cm below the midpoint of this line. The analysis of variance revealed significant differences between the electrode positions during the short 20% MVC and during MVC (P ≤ 0.01). Furthermore, lower rms values were found when the electrodes were placed symmetrically around the midpoint of the reference line, which confirms previous studies. A statistical model has been developed to discriminate additionally the very small changes in the electromyogram parameters due to electrode position during the sustained 20% MVC. It was found that the slope coefficients of rms and MPF were significantly different from 0 (P ≤ 0.01), although to a lesser degree for rms and more clearly for MPF of the caudal position (P ≤ 0.05). Furthermore, significant differences were found between several combinations of the uppermost electrodes and the caudal position (P ≤ 0.01). From this study, it is concluded that it is important to evaluate several electrode positions on the upper trapezius muscle to be able to represent the behaviour of this muscle accurately during a sustained contraction.

Perceived Discomfort and Electromyographic Activity of the Upper Trapezius While Working at a VDT Station

Ten female participants performed work at a video display terminal (VDT) station over a whole working day. Subjective local muscular fatigue was evaluated by means of the Category Ratio 10 scale. Electromyographic activity of the upper right and left trapezius was measured. A comparison was made between 5 participants who had previous complaints and 5 participants who reported no musculoskeletal problems in the shoulder-neck region. The subjective scores for the shoulder differed significantly between the two groups, being higher for the group with complaints. Both groups showed a decrease in discomfort after the lunch break. The activity of the trapezius increased significantly for both groups, in a more pronounced way for the group with disorders. Although it is found in literature that VDT work is a task with very low static loads, it seems from this study that the EMG activity increase can be an indication of muscle fatigue: More effort was required to accomplish the same VDT task at the end of the day.

Relation between differences in electromyographic adaptations during static contractions and the muscle function

This study determines whether changes in the EMG values of two important muscles of the shoulder and neck region, the anterior deltoid and the upper trapezius, are due to changes in torque production or due to fatigue processes during sustained activity. Contractions at 20, 40, 60, 80 and 100% MVC were performed during a flexion of the arm in the sagittal plane at 90 degrees, to examine the relation between torque and EMG. A sustained contraction at 20% MVC was performed to endurance point in the same position. RMS, a new parameter called activity, (ACT), and MPF of the deltoid anterior and the upper trapezius were analysed. The amplitude values correlated highly with increasing torque production, both for the deltoid muscle (range r = 0.95-0.96), and the trapezius muscle (range r = 0.83-0.87), whereas no significant difference was found for MPF. For the endurance task, the decrease in MPF was far more pronounced for the deltoid than for the trapezius, whereas the opposite occurred with RMS (P < or = 0.01). Furthermore, there was no significant difference over time for the ACT values of the deltoid, whereas there were significant increases in ACT for the trapezius (P < or = 0.01). The RMS/ACT ratio correlated highly (r = 0.81) with the MPF. Regression coefficients of these parameters differed significantly for the trapezius muscle but not for the deltoid muscle. Therefore, the RMS/ACT ratio may be extremely important in analysing the fatigue effects during sustained efforts, independent of torque variations, which can influence indicators of fatigue.

Influence of material handling devices on the physical load during the end assembly of cars

Abstract The effect of using a mechanical device on physical load was analysed during the end assembly of cars. Five tasks, further sub-divided into lifting and positioning, were performed by someone experienced in working with and without the mechanical tool. A practical methodology was used: the subjective walk and talk through method, the NIOSH equation (1991), a three-dimensional goniometer (Back Tracker) and surface electromyography (EMG) of the relevant muscle groups. According to the NIOSH equation, 8 out of 10 of the tasks should only be performed by trained workers and preferably with tools. The Back Tracker revealed that the mechanical tools reduced posture angles significantly ( p ⩽0.05) for installing the windows, but not for left lateroflexion during pre-assembly of windows. It was clear from the EMG analysis that using tools did not always decrease muscular activity significantly. In general, the appropriateness of each tool needs to be evaluated separately taking the subjective criteria into account. Relevance to industry In this study, the relevance of using a mechanical device to reduce the physical load during car assembly, is evaluated. As the tools are expensive, it is important to the industry whether they are being used and how efficient they are.

Effectiveness of Specific Lifting Techniques and Tools on Workload in a Lifting Situation – A Case Study

A lot of workers complain of backache, muscular pains and working in painful or tiring postures [1]. To reduce workload and consequently the drop out of workers due to these complaints, companies adapt the work place, provide tools and/or give training. The objective of this study is to investigate in a real working environment during picking of boxes, the effect of using good lifting techniques and/or work height adjustments on the physical workload.

Hoe interventies ter preventie van musculoskeletale aandoeningen en psychosociale risico’s opzetten?

SamenvattingIn het kader van een onderzoek naar interventies om psychosociale risico’s en musculoskeletale aandoeningen aan te pakken, werd een studie uitgevoerd in 24 Belgische organisaties. Volgende aandachtspunten worden besproken: het belang van algemene risicoanalyses, soorten van interventies, betrokkenen in de interventie, effectiviteit en efficiëntie en bevorderende en belemmerende factoren voor het doorvoeren van een succesvolle interventie. De resultaten van deze studie kunnen niet als volledig representatief beschouwd worden, maar toch kunnen belangwekkende aanbevelingen voor de praktijk getrokken worden vermits de gevalstudies uit diverse bedrijfsgrootten en sectoren komen: een beleidsmatige aanpak kan groeien uit concrete interventies; meerdere interventies worden doorgevoerd om tot preventie te komen; management is belangrijk als initiatiefnemer; participatieve inbreng van werknemers is cruciaal; kosten-baten analyses worden te weinig doorgevoerd.SummaryWithin the framework of a research project on interventions for the prevention of psychosocial risks and musculoskeletal disorders, a study was performed in 24 Belgian organisations. The following topics are addressed: the importance of general risk analysis, types of interventions, stakeholders in the intervention, efficacy and efficiency, barriers and facilitators of a successful intervention. The results of this study cannot be considered as completely representative, but important conclusions can be drawn since the case studies are drawn from companies of different sizes and sectors: a global policy approach can result from specific interventions; a mix of interventions can be organized for reaching prevention; management as initiator is a key point; participation of employees is crucial; cost-benefit analysis is missing in practice.

Participatieve managementstrategie voor het beheer van gezondheids-, veiligheids- en welzijnsrisico’s

SamenvattingDit artikel beschrijft een strategie voor een coherent en efficiënt preventieprogramma op het vlak van welzijn op het werk vanuit een participatieve benadering. Deze globale benadering is niet alleen noodzakelijk op één werkplek, maar ook voor het geheel van de arbeidsomstandigheden op het werk.