[Efficacy of a chair with magnets in the prevention of musculo-skeletal disorders caused by prolonged sitting].
The aim of the present paper was to evaluate the effectiveness of a sitting system based on the application of magnetic fields in the prevention of posture-related musculoskeletal disorders. We studied 5 healthy male volunteers during laboratory simulation tests including 60-minute sessions of "driving" and computer-work. Two subjects performed a 60-minute driving test on an isotonic dynamometer with a steering wheel, in which they had to steer for 2 min and drive normally for 3 min, alternatively. They repeated the test with and without the magnet-based sitting system. Three subjects performed a 60-minute computer-work test in a seated position with and without the magnet-based sitting system. EMG activity was registered in the trapezius muscles and at L1 and L5 lumbar level bilaterally with surface electrodes. The EMG trapezius activity continuously recorded was analysed with the APDF method, as proposed by Jonsson. Before and after the tests, the subjects performed a 60-sec isometric back extension at 60% MVC with a specific back dynamometer, while paraspinal EMG was recorded. The slope of decay of the median frequency of the EMG power spectrum was then calculated as an index of localised muscle fatigue. The results showed a decreased myoelectric activity both at shoulder and lumbar level by using the magnet-based sitting system for prolonged seated work tasks. Thus, the system appears to be an effective tool in preventing muscle contractures secondary to prolonged, constrained positions.
Centro Studi Attività Motorie (CSAM), Fondazione S. Maugeri, IRCCS, Pavia.
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D000328:Adult; D004576:Electromyography; D006801:Humans; D008280:Magnetics / Q000627:therapeutic use*; D009140:Musculoskeletal Diseases / Q000209:etiology* / Q000517:prevention & control*; D009784:Occupational Diseases / Q000209:etiology* / Q000517:prevention & control*; D011187:Posture; D013997:Time Factors