ABSTRACT
Musculoskeletal disorders (MSDs) are widespread and occur in all kind of jobs. The most strenuous tasks, which are the cause of MSDs are those characterized by static load of muscles and those which involve repetitive tasks performance. Data related to musculoskeletal load in work conditions as well as tools aimed at musculoskeletal load assessment provides occupational biomechanics. Methods, which serve to musculoskeletal load assessment can refer to external or internal load of musculoskeletal system. For internal load assessment well established and widespread method is electromyography. Fatigue assessment at low level force meets difficulties. An algorithm based on approximation function, which can be applied in fatigue analysis of EMG signal registered at low level of muscle contraction. Since there is a strong link between MSDs rate and occupational involvement in repetitive tasks of upper limbs, method dedicated especially to repetitive tasks, has been developed on the basis of seven degrees of freedom model of upper limb model and parameters, which characterize cycle load. In conclusion it
Keywords: occupational biomechanics, electromyography, repetitive tasks, muscle forces
Epidemiological studies seek to identify association between the development of MSDs and musculoskeletal load during performing work tasks. Numerous studies are conducted in Europe and worldwide to investigate potential interactions between physical and psychosocial risk factors in the workplace with symptoms of musculoskeletal disorder of the back, neck, lower and upper limbs. The main role in providing data related to musculoskeletal load in work conditions as well as tools aimed at musculoskeletal load assessment plays occupational biomechanics. One of the most strenuous tasks, which arc the cause of MSDs are those characterized by static load of muscles and those which involve repetitive tasks performance. Many studies proved that performing such tasks at even very low levels of load can be crucial factor in MSDs development. Solutions regarding optimum load of the human musculoskeletal system in occupational conditions are obtained as a result of research with application of various methods. Musculoskeletal load can be referred to as extemal or internal load. External load is assessed as dependant on parameters related to body posture, exerted forces and time sequences. Intemal load measures reflect reaction of human body on the exerted external load. It means that the later expresses both external load related to work place and individual characteristic of the worker including age, gender or health. External load is assessed using various methods which assess load based on the parameters describing positions of separate body clements, force exerted by a worker and time sequences of load. Intemal load and worker's fatigue may be assessed using such methods as the analysis of blood pressure, energy expenditure or the analysis of an electric signal characterising muscle contraction, namely surface electromyography.
