Efficacy of a chair with magnets in the prevention of musculo-skeletal disorders caused by prolonged sitting.
Capodaglio P, Vicenzi G.
Centro Studi Attivita Motorie (CSAM), Fondazione S. Maugeri, IRCCS, Pavia.
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
G Ital Med Lav Ergon 2000 Oct-Dec;22(4):332-6