Protocol A included 10 participants and comprised measurements of blood flow velocity, blood pressure and heart rate, the functional near infrared spectroscopy (fNIRS) measurement, and the ECG measurement.
Protocol B included 16 participants (6 from protocol A) for flow-mediated dilation measurements.
Each crossover trial for each participant was performed twice on different days after a washout period of at least two days and the data were averaged for each individual in each test.
Exposure duration: 15 min
Exposure duration: 30 min
|Setup||two separate electromagnetic coils (inner diameter 20 mm, outer diameter 50 mm, and height 60 mm) were set horizontally inside the magnetic field exposure device and the distance between the centers of the double induction coils was 160 mm|
|Sham exposure||A sham exposure was conducted.|
|magnetic flux density||180 mT||maximum||calculated||-||on the surface of the magnetic field exposure device above the centers of the coils|
|magnetic flux density||127 mT||effective value||measured||-||-|
|magnetic flux density||13 mT||maximum||-||-||in the ulnary artery|
|magnetic flux density||8 mT||maximum||-||-||in the brachial artery|
|magnetic flux density||5 mT||maximum||-||-||in carotid artery|
|cf. remarks||-||-||-||-||induced peak electric field strength in the skin of the upper arm: 491.7 mV/m (additional values for different tissues are provided in the article)|
|Exposure duration||30 min|
|Additional info||protocol B|
In 50 Hz magnetic field and sham exposures, the heart rate values and diastolic blood pressure were not significantly changed from the baseline values and there was no significant difference between both conditions. However, participants who received three regional different magnetic field exposures had significantly increased ulnar arterial blood flow velocity compared to the sham exposures during and after exposures. Furthermore, after muscle loading exercise, magnetic field exposure recovered hemoglobin oxygenation index values faster and higher than sham exposure. Moreover, participants exposed to the magnetic field in the neck region had significantly increased parasympathetic high-frequency activity relative to the sham exposure during and after exposure. The magnetic field exposure in the upper arm region significantly increased the brachial artery flow-mediated dilation compared to the sham exposure.
This study provides the first evidence that a 50 Hz magnetic field can activate parasympathetic activity and thereby lead to an increased vasodilation and blood flow via a nitric oxide-dependent mechanism. The therapeutic implications of these findings require further preclinical and clinical investigations.