Repetitive and monotonous work is frequently associated with neck and shoulder pain and negative psychosocial factors inducing stress reactions. The present thesis concerns the relations between psychophysiological and subjective stress reactions, muscle activity measured by surface electromyography (SEMG) in the trapezius muscle, and neck and shoulder pain in women performing repetitive and monotonous work. In Study I cardiovascular and subjective stress reactions were investigated during computer work in a laboratory setting. The findings indicated that heart rate variability is a more sensitive and selective measure of mental stress compared with blood pressure recordings. Study II explored the relations between stress reactions and muscle activity during supermarket work. The results showed that perceived negative stress reactions may have a specific influence on muscle activity in the neck and shoulder region, which can be of importance for work-related musculoskeletal disorders in repetitive and monotonous work. In Study III the association between SEMG activity patterns and neck and shoulder pain was investigated during cash register work. It was found that pain-afflicted women had a different muscle activation pattern (more static, more co-contraction, less muscle rest) compared with pain-free women. Study IV was a follow-up study evaluating the introduction of job rotation among female cashiers. The results indicated positive effects on diastolic blood pressure, muscle activity, and partly on neck and shoulder pain, although perceived stress was unchanged. It was concluded that job rotation seems to have a limited effect on chronic neck and shoulder pain, but may be an effective preventive measure. The empirical findings are particularly relevant for women who, compared with men, more often perform repetitive and monotonous work and are also more often affected by neck and shoulder pain.

Submitted by Nadir Basilio (nadirsb@uninove.br) on 2018-06-19T13:41:01Z No. of bitstreams: 1 Fabiana Sarilho de Mendonca.pdf: 960484 bytes, checksum: be95fe89cc95556dccc9a63e7868ac13 (MD5) / Made available in DSpace on 2018-06-19T13:41:01Z (GMT). No. of bitstreams: 1 Fabiana Sarilho de Mendonca.pdf: 960484 bytes, checksum: be95fe89cc95556dccc9a63e7868ac13 (MD5) Previous issue date: 2015-12-15 / Although the low level light therapy (LLLT) irradiation is indicated for a variety of musculoskeletal disorders like muscle fatigue, tissue repair and as anti-inflammatory agent, its effects on muscle activity are still poorly understood. The objective of this study was to evaluate the immediate effect of LLLT of irradiation on the nerve conduction velocity and electromyographic activity of the muscle upper trapezius (UT) in healthy subjects. Twenty healthy women (mean age 23.54  2.51) were included in this study, cross-over, controlled, randomized, double blind. Each volunteer has received two types of treatment with continuous LLLT (LLLT) and the other one with LLLT placebo (LLLTP). The treatment order was randomized by raffle, being included an interval of 7 days between each laser intervention (wash-out) to prevent residual effects. The surface electromyography (EMG) was used to verify the nerve conduction velocity (CV) and muscle activity UT during shoulder elevation in isometric contraction to 5 different levels of contraction (10, 15, 20, 25, 30% of maximum voluntary contraction), via visual feedback provided through a driving line. The collects of the EMG signal were performed before and after 30 minutes of treatment (LLLT or LLLTP). In the analysis of variance for repeated measures (ANOVA) it was possible to observe a significant decrease in the amplitude of the EMG signal to treatment with LLLT (p = 0.0001) but not to the placebo treated group (p < 0.05). Regarding of the CV, no change was observed for both treatments (LLLT: p > 0.05; LLLTP: p > 0.05 - ANOVA). In this study it could be observed an immediate effect of LLLT irradiation on the amplitude of the electromyographic signal of the trapezius muscle descending fibers in healthy individuals, but not on the nerve conduction velocity. / Embora a irradiação com laser de baixa potência (LBP) seja indicada para vários tipos de disfunções musculoesqueléticas como fadiga muscular, reparo tecidual e como agente anti-inflamatório, seus efeitos sobre a atividade muscular ainda são pouco conhecidos. O objetivo desse estudo foi avaliar o efeito imediato da irradiação do LBP sobre a velocidade de condução nervosa e a atividade eletromiográfica do músculo trapézio fibras descendentes (TFD) em indivíduos saudáveis. Vinte mulheres saudáveis (idade média: 23,54  2,51) foram incluídas nesse estudo, cruzado, controlado, randomizado duplo cego. Cada voluntária recebeu 2 tipos de tratamento com LBP (LBP) contínuo e outra com LBP placebo (LBPP). A ordem de tratamento foi randomizada por sorteio, sendo incluído um intervalo de 7 dias entre cada intervenção de laser (wash-out) para evitar efeitos residuais. A eletromiografia (EMG) de superfície foi utilizada para verificar a velocidade de condução nervosa (VC) e atividade no músculo TFD durante a elevação do ombro em contração isométrica em 5 diferentes níveis de contração (10, 15, 20, 25, 30% da contração voluntária máxima), por meio de feedback visual proporcionado por uma linha de treino. As coletas do sinal EMG foram realizadas antes e após 30 minutos do tratamento (LBP ou LBPP). Na análise de variância para medidas repetidas (ANOVA) foi possível observar diminuição significativa na amplitude do sinal EMG para o tratamento com LBP (p = 0,0001) porém não para o grupo tratado com LBPP (p < 0,05). Em relação à VC, nenhuma alteração foi observada para ambos os tratamentos (LBP: p > 0,05; LBPP: p > 0,05 - ANOVA). Nesse estudo foi possível observar um efeito imediato da irradiação com LBP sobre a amplitude do sinal eletromiográfico do músculo trapézio fibras descendentes em indivíduo saudáveis, porém, não sobre a velocidade de condução nervosa.