n Ergonomics SA : Journal of the Ergonomics Society of South Africa - The effects of posture and cognitive information processing from different sensory modalities on perceived musculoskeletal discomfort and work performance

Volume 25, Issue 2
  • ISSN : 1010-2728



Physical work exposures often include having to maintain awkward, static postures for sustained periods of time, which ultimately result in the onset of local muscle fatigue and accompanied symptoms of discomfort. Perceived discomfort has been suggested to trigger the realization for recovery of depleted resources. However, various authors predict that distraction, offered by concurrent cognitive engagement, causes perceptions of discomfort to be over-ridden. On the contrary, intense symptoms of discomfort/pain have been reported to disrupt cognitive processing and lower work performance. This study focused on the influence of time, awkward posture, and cognitive processing utilizing different senses (auditory and visual) on measured physical, perceptual and performance responses. The experimental procedure required participants (n=20) to carry out five conditions of four minutes each. Conditions involved; (1) either adopting a static 30° stooped trunk posture, or (2) performing a cognitive task (seated), utilizing either the visual or auditory senses, or (3) a combination of posture and cognitive task. Measured responses included; heart rate (HR), electromyography (EMG), heart rate variability (HRV), perceived discomfort, and performance (% error and reading speed). Results indicate that, apart from the percentage of error incurred, the influence of modality had no significant effect on any of the measured responses, irrespective of time and posture assumed. Exposure to an awkward posture, designed to induce muscular discomfort, had a significant impact on measured HRV during the visual condition. The addition of a stooped posture caused a significant improvement in auditory performance, during the first two minutes. Apart from this unexpected finding, which can be explained by the order of permutation, induced muscular discomfort caused no significant decrements in performance. Performance and HRV remained relatively unaffected by the influence of time. However, perceptions of body discomfort (BD) increased significantly from minute two to four.

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