To study possible changes in heart rate and heart rate variability due to 50 Hz magnetic fields under conditions of provocation of the sympathovagal cardiac control system, being the conditions under which environmental effects may exert their maximal influence.
Passive tilting was used to obtain a situation wherein sympathetic neural control was increased and physiological disturbance was minimized. Passive tilt provides a non-invasive method for quantifying the sympathovagal balance as it involves a minimal engagement of central drive and muscular activity and is compatible with quite accurate stationary conditions suitable for spectral analysis.
The tilt procedure involves passively altering a subject's position from supine to a predefined angle (in healthy subjects passive tilt causes an increase in low frequency heart rate variability and an increase in sympathetic modulation of heart rate).
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
continuous for 15 min
|
|
| Frequency | 50 Hz |
|---|---|
| Type | |
| Waveform | |
| Polarization |
|
| Exposure duration | continuous for 15 min |
| Additional info | Power frequency magnetic field relevant to industrial exposure. |
| Exposure source |
|
|---|---|
| Setup | Subjects were loosely strapped to a table which was tilted at 60°. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 28 µT | unspecified | unspecified | - | - |
The sympathovagal balance during tilt remained the same during both sham exposure and magnetic field exposure (there were no significant differences in the measured parameters). The data suggest that situations of sympathetic dominance do not increase the sensitivity of sympathetic neural heart rate variablity control mechanims to magnetic field exposure in the conditions used in the current experimental protocol.
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