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Comparison of four specific dynamic office chairs with a conventional office chair: Impact upon muscle activation, physical activity and posture

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Author: Ellegast, R.P. · Kraft, K. · Groenesteijn, L. · Krause, F. · Berger, H. · Vink, P.
Source:Applied Ergonomics, 2, 43, 296-307
Identifier: 442915
doi: doi:10.1016/j.apergo.2011.06.005
Keywords: Workplace · Dynamic office chairs · EMG · Physical activity · Posture · VDU/computer workplace · Dynamic elements · EMG · Erector spinae · Muscle activation · Office chair · Physical activity · Posture · Risk factors · Sitting posture · Structural elements · Activation analysis · Muscle · Dynamics · adult · article · biomechanics · body posture · chair · controlled study · electromyogram · equipment design · erector spinae muscle · ergonomics · female · human · human experiment · job performance · joint angle · male · muscle contraction · musculoskeletal system parameters · normal human · office chair · physical activity · sitting · skeletal muscle · trapezius muscle · Work and Employment · Healthy Living · Organisation · SP - Sustainable Productivity · BSS - Behavioural and Societal Sciences


Prolonged and static sitting postures provoke physical inactivity at VDU workplaces and are therefore discussed as risk factors for the musculoskeletal system. Manufacturers have designed specific dynamic office chairs featuring structural elements which promote dynamic sitting and therefore physical activity. The aim of the present study was to evaluate the effects of four specific dynamic chairs on erector spinae and trapezius EMG, postures/joint angles and physical activity intensity (PAI) compared to those of a conventional standard office chair. All chairs were fitted with sensors for measurement of the chair parameters (backrest inclination, forward and sideward seat pan inclination), and tested in the laboratory by 10 subjects performing 7 standardized office tasks and by another 12 subjects in the field during their normal office work. Muscle activation revealed no significant differences between the specific dynamic chairs and the reference chair. Analysis of postures/joint angles and PAI revealed only a few differences between the chairs, whereas the tasks performed strongly affected the measured muscle activation, postures and kinematics. The characteristic dynamic elements of each specific chair yielded significant differences in the measured chair parameters, but these characteristics did not appear to affect the sitting dynamics of the subjects performing their office tasks. © 2011 Elsevier Ltd and The Ergonomics Society.