This study investigates how altering wrist posture influences the relationship between the time and frequency measures of the electromyography (EMG) signal of extensor digitorum communis (EDC) and flexor carpi ulnaris (FCU). Thirteen participants exerted handgrip force related to maximum voluntary contraction (MVC) in four tests: 20%MVC and 50%MVC in neutral wrist posture and 20%MVC in full wrist flexion and extension. EMG measurements from EDC and FCU were used to calculate normalized values of amplitude (nRMS) and mean and median frequency of the power spectrum (nMPF, nMF). During muscle shortening (wrist flexion for FCU and wrist extension for EDC) nRMS was approximately twofold higher than in neutral posture for FCU and fourfold for EDC. All measures obtained at 20%MVC in neutral posture were significantly different from 20%MVC in wrist flexion for FCU and 20%MVC in wrist extension for EDC (p<0.05). Differences between 50%MVC and 20%MVC at neutral posture (nRMS) were significant for both muscles, although in nMPF and nMF for EDC only. Muscle shortening changed the pattern of statistical significance when the time and frequency domain measures were compared, whereas muscle lengthening did not. It can be concluded that muscle shortening caused by altering wrist posture influences the relationship between the time and frequency measures in both muscles. This suggests that in studies using EMG in different wrist postures, changes in the relationship between the time and the frequency measures should be considered.

The aim of the study was to investigate the possibility of using infrared (IR)

Objectives. The aim of this study was to identify major determinants for neck and lower back pain (LBP) among office workers of different ages. Methods. Computer workers (N = 2000) responded to a questionnaire on demographics, musculoskeletal disorders (MSDs), lifestyle characteristics, ergonomics of computer work and psychosocial and physical job characteristics. Results. Over 48% of respondents complained of MSDs last year, in particular neck pain and LBP. The results of logistic regression analysis revealed that prolonged computer time (odds ratio [OR] 1.92) and increased job demands (OR 1.06) were likely to increase the risk of neck pain, while social support (OR 0.96) and the use of seat-plate height adjustment (OR 0.64) would help to reduce the risk. Risk factors for LBP included smoking more than 14 cigarettes a day (OR 2.21), long hours spent working with a computer (OR 1.94), increased physical exertion at work (OR 1.29), increased work demands (OR 1.03) and older age (OR 1.03). Conclusions. The most effective way to eliminate MSD hazards in the workplace is to develop health programmes aimed at advocating healthy lifestyle behaviours and raising workers' awareness of workstation ergonomics and work organization, especially for women and older workers.

We focused on physiological and muscle tension measures differentiating work according to the level of mental demands. Differences in sustained attention, vigilance and maintaining posture only proved that mental demands were mostly reflected by tension in arm and shoulder girdle muscles and, to a lesser degree, in forearm muscles.

The aim of this study was to analyse the electromyographic (EMG)