STUDY DESIGN In vivo feline model subjected to variable number of repetitions of a short static lumbar flexion followed by an equally long rest period. OBJECTIVES The purpose of this study was to determine the influence of the number of repetitions as a risk factor in promoting a cumulative low back disorder in the feline model. SUMMARY OF BACKGROUND DATA Epidemiologic data point out that t...

The purpose of the study was to analyse the influence of the precision of a task on tension and fatigue of the trapezius and deltoid muscles. Ten young men took part in experiments. Different levels of force and different frequencies of pressing a button defined the precision of the task. Surface electromyography (EMG) was used. Muscle tension and fatigue were reflected by 2 parameters of the E...

We study the existence of distinct failure regimes in a model for fracture in fibrous materials. We simulate a bundle of parallel fibers under uniaxial static load and observe two different failure regimes: a catastrophic and a slowly shredding. In the catastrophic regime the initial deformation produces a crack which percolates through the bundle. In the slowly shredding regime the initial def...

background: work-related musculoskeletal disorders are the most important problems in the health workforce. these discomforts cause many working days losses, increase absenteeism from work, and impose annual economic costs. awkward posture is the most important factor among the risk factors for work-related musculoskeletal disorders. this study aimed at implementing an interventional ergonomic ...

in the current engineering practices, buildings are commonly designed for an effective lifetime of 50 years. this lifetime can increase the cost of buildings with short lifetimes and can reduce the safety level of buildings with large lifetimes. in this paper, a “service-life factor” has been defined. applying this factor into the nominal values of live, earthquake, wind, and snow loads, the ef...

Spring-mass models have been used to characterize running mechanics and leg stiffness in a variety of conditions, yet it remains unknown how running while carrying a load affects running mechanics and leg stiffness. The purpose of this study was to test the hypothesis that running with a load increases leg stiffness. Twenty-seven subjects ran at a constant speed on a force-measuring treadmill w...

AIMS (1) To find a universal strategy for the identification of specific demands of a job or task, focusing on occupations in which there may be an increased risk for health complaints owing to these specific demands. (2) To select reliable and valid tests concerning lifting, pushing, and pulling, which consider the relation between occupational work demands and the assessment of the maximally ...

The estimation of muscle forces in musculoskeletal shoulder models is still controversial. Two different methods are widely used to solve the indeterminacy of the system: electromyography (EMG)-based methods and stress-based methods. The goal of this work was to evaluate the influence of these two methods on the prediction of muscle forces, glenohumeral load and joint stability after total shou...

Although it is generally assumed that mental stress induces muscular tension, the experimental data have, so far, been inconclusive. Likely explanations for these inconsistent findings are (a) too small subject samples in some experiments, (b) the use of only one type of stress stimulation, and (c) the lack of objective (physiological) measurements documenting the stress-inducing properties of ...

BACKGROUND Schoolchildren usually use school bags to carry their school materials. Carry-ing heavy school bags can cause several problems such as musculoskeletal problems among schoolchildren. The aim of this study was to investigate the association between the weight of school bags and the occurrence of low back, shoulder and hand/wrist symptoms among pri-mary school children. METHOD This cr...