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Four shoulder muscles (the supraspinatus, the infraspinatus, the anterior and middle portion of the deltoid, and the descending part of the trapezius) were examined with electromyography in abducted arm positions. By using feedback techniques, we found that the subjects could reduce the EMG activity voluntarily by 22-47% in the trapezius muscle while(More)
A method to investigate the rhythm of the human shoulder, i.e. the interplay between the motion of constituent parts of the shoulder, has been devised and tested. The method is based upon numerical evaluation of low dose roentgenstereophotogrammetric motion pictures of subjects equipped with radiation dense implantations in the bones. Evaluation of the(More)
In a first step of a biomechanical modelling of the human shoulder the points of application of muscle forces to the bones were determined in a dissection study on four human shoulder specimens. A kinematic description of the shoulder was presented employing bone fixed coordinate systems. Actions of the shoulder muscles were modelled as a system of forces(More)
The problem of the increasingly common shoulder pain syndromes in industry was investigated by biomechanic and epidemiologic methods. Rotator cuff tendinitis constitutes a major problem in people with arduous occupations, i.e., shipyard welders (prevalence ratio, 18.3%), and steel plateworkers (16.2%). Static work seems to induce symptoms at an earlier age.(More)
A three-dimensional biomechanical model of the shoulder is developed for force predictions in 46 shoulder structures. The model is directed towards the analysis of static working situations where the load is low or moderate. Arbitrary static arm postures in the natural shoulder range may be considered, as well as different kinds of external loads including(More)
For the first time it is clearly exhibited that synovial fluid (SF) is thixotropic. Although no hysteresis loops were observed for SF, not even at high shear rates, thixotropy may be exhibited by measuring the rate of recovery after extensive shearing. The rebuilding of the structure in a small-amplitude oscillatory state following the high-shear-rate state(More)
In ergonomic and biomechanic research, estimations of shoulder muscle load and evaluation of different measuring techniques are important. Intramuscular pressure (IMP), using the microcapillary infusion technique and bipolar intramuscular electromyography (EMG), was recorded from the same part of the supraspinatus muscle. In 12 subjects, IMP and EMG were(More)
In this study the fluid gradient chamber, a modified version of the Boyden chamber that enables mobile gradients, was used to study the migration of human granulocytes in gradients of fMLP. Temporal chemotactic gradients were created by moving density-stabilized spatial gradients at different velocities in relation to migrating cells. Random and directed(More)
Strength profiles of the shoulder joint are measured experimentally for two arm positions in "the scapular plane" in order to present quantitative data on the shoulder strength. Apart from yielding the actual force a subject can exert in various directions, these measurements also exhibit e.g. the strongest and weakest directions, in fact the relative(More)
Leukocyte migration in vitro has been studied extensively during many years without providing satisfactory theoretical models for the different migratory behaviors (chemotaxis and chemokinesis) of leukocyte populations. The present study utilized the fluid gradient chamber, which is a new method to study leukocyte migration in filters. Human neutrophils(More)
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