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Medical/biological study (experimental study)

Effect of a low intensity magnetic field on human motor behavior.

Published in: Bioelectromagnetics 2005; 26 (8): 657-669

Aim of study (acc. to author)

To determine the effect of a 50 Hz magnetic field (1000 µT) centered at the level of the head on human motor behavior (physiological tremor).
Background/further details: Physiological tremor can be defined as an involuntary, irregular, and continuous movement of body's extremities. It is characterized by its amplitude and by its frequency. Tremor occuring while people have to maintain a posture (postural tremor) and tremor occuring during a goal-directed movement (kinetic tremor) seem to imply different neural pathways.
24 men recruited among the personnel of the French company, Electricité de France, completed the experiment.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 50 Hz
Exposure duration: 4 times 14 min with a 3 min interval between them = 65 min; 4 on/off transitions during each 14 min sequence
General information
the following conditions were tested: i) postural tremor under real exposure ii) postural tremor under sham exposure iii) kinetic tremor under real exposure iv) kinetic tremor under sham exposure.
Exposure 1
Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration 4 times 14 min with a 3 min interval between them = 65 min; 4 on/off transitions during each 14 min sequence
Exposure setup
Exposure source
  • two parallel 1.6 m side square coils, 1.1 m apart
Setup A subject sat on a plastic chair placed in the middle of the MF generating device which generated a continuous and homogeneous MF centered at the level of the head, but the trunk and arms were also exposed.
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1 mT unspecified calibration - -
Exposed system:
  • human
  • partial body: head (trunk and arms)

Methods Endpoint/measurement parameters/methodology

Investigated material:
Time of investigation:
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

No effect of the magnetic field was revealed for kinetic tremor.
Concerning postural tremor, the proportion of oscillations at low frequencies (between 2 and 4 Hz) was higher during the real exposure than during the sham exposure sequence.
It is suggested that magnetic field could have a subtle delayed effect on human behavior, which is clearly not pathological. These findings should be taken into account for the establishment of new exposure limits.
Study character:

Study funded by

  • Hydro-Québec, Canada

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