| Assessment |
| Primary outcomes |
Measurement of blood flow velocity was conducted under one of three types of regional exposures, i.e., forearm exposure, upper arm exposure and neck exposure to a 50 Hz MF at Bmax 180 mT/Brms 127 mT on the surface of the MF exposure device. The MF or sham exposure was performed continuously for 15 min. In all cases of exposures, an ultrasound probe was positioned on the ventral skin surface of the bared left forearm to assess the blood flow velocity in an ulnar artery. In the case of forearm exposure, after putting on the dorsal side of the left forearm on the MF exposure device for about 5 min, the blood flow velocity (peak systolic velocity [PSV] in pulsed wave [PW] mode) in an ulnar artery was measured noninvasively from the ventral side of the forearm at 5-min intervals for 25 min by using a potable digital color Doppler ultrasound system (JS2 with a linear probe L741, 5-12 MHz, Medicare Co., Ltd., Shenzhen, China).
The forearm was positioned on an MF exposure device for about 30 min to keep the arm motionless as long as possible during the clinical trial in each subject. At each time point, the PSV was measured in triplicate for the blood flow velocity and the mean values was calculated. For upper arm exposure, an additional second MF exposure device was positioned to the dorsal side of the upper arm. For neck exposure, an additional third MF exposure device was positioned laterally to the dorsal side of the neck. In the cases of upper arm and neck exposure experiments, the MF exposure device for forearm exposure was used to keep posture the same as in the case of forearm exposure experiment without turning on the power. Each crossover trial for each participant was performed twice on different days after a washout period of at least two days and the duplicate data were averaged for each individual in each test. Therefore, the mean value of two trials in MF or sham exposure was used for statistical analysis. |
| Key secondary outcomes |
The ECG monitoring was conducted under neck exposure alone. ECG was recorded continuously for 25 min using a multi-channel telemetry system (WEB-1000, Nihon Kohden Co., Ltd., Tokyo, Japan). The MF or sham exposure was conducted continuously for 15 min. RRI was extracted and used in this analysis. A power spectral analysis of RRI by fast Fourier transformation was performed to obtain the low-frequency (LF) and high-frequency (HF) components and the HF component and the LF/HF ratio were analyzed.
FMD is an index of artery endothelium-derived nitric oxide function. The brachial artery FMD measurement was performed using an FMD monitoring device (UNEXEF18G; UNEX Co., Ltd., Nagoya, Japan). Exposure of the dorsal side of the left upper arm was performed with the subject lying on a bed in the supine position. The brachial artery FMD values in the left upper arm was monitored at the baseline (pre-exposure) and post-exposure. After putting on the dorsal side of the left upper arm on an MF exposure device and attaching the cuff around the left forearm, the FMD values were monitored before and immediately after exposures. FMD test was repeated with an interval of 30 min and the MF or sham exposure was conducted continuously for 30 min.
After the muscle loading exercise, hemoglobin oxygenation index values were measured and analyzed using a functional near-infrared spectroscopy (fNIRS) device (Pocket NIRS Duo, DynaSense, Hamamatsu, Japan).
To conduct muscle loading exercises, the participants in sitting position performed the wrist curl exercise (3 sets of 20 repetition cycles) in their left hand using a 3kg dumbbell.
MF exposure to the left forearm was carried out for 15 min.
|
| Intervention |
| No. of arms |
6 |
| Purpose of intervention |
Treatment |
| Type of intervention |
|
| Interventions/Control_1 |
Effects of forearm exposure to magnetic field (MF) on ulnar arterial blood flow velocity. The MF or sham exposure is conducted continuously for 15 min. |
| Interventions/Control_2 |
Effects of upper arm exposure to MF on ulnar arterial blood flow velocity. The MF or sham exposure was conducted continuously for 15 min.
|
| Interventions/Control_3 |
Effects of neck exposure to MF on ulnar arterial blood flow velocity. The MF or sham exposure was conducted continuously for 15 min. |
| Interventions/Control_4 |
Effects of neck exposure to MF on ECG. The MF or sham exposure was conducted continuously for 15 min. |
| Interventions/Control_5 |
Effects of upper arm exposure to MF on brachial artery flow-mediated dilation (FMD). The MF or sham exposure was conducted continuously for 30 min. |
| Interventions/Control_6 |
Effects of forearm exposure to MF on hemoglobin oxygenation index after muscle loading exercise in forearm. The MF or sham exposure was conducted continuously for 15 min. |
| Interventions/Control_7 |
|
| Interventions/Control_8 |
|
| Interventions/Control_9 |
|
| Interventions/Control_10 |
|
| Result |
| URL related to results and publications |
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0255242 |
| Number of participants that the trial has enrolled |
20 |
| Results |
1)Forearm, upper arm, or neck exposure, had significantly increased ulnar arterial blood flow velocity compared to the sham exposures.
2)After muscle loading exercise, MF exposure recovered hemoglobin oxygenation index values faster and higher than sham exposure.
3)MF exposure in the neck region had significantly increased parasympathetic high-frequency activity relative to the sham exposure.
4)The MF exposure in the upper arm region significantly increased the FMD compared to the sham exposure. |
| Results date posted |
| 2021 |
Year |
12 |
Month |
10 |
Day |
|
| Results Delayed |
|
| Results Delay Reason |
|
| Date of the first journal publication of results |
| 2021 |
Year |
08 |
Month |
05 |
Day |
|
| Baseline Characteristics |
The inclusion criteria were as follows:
1) participants have not used any form of physical therapy and have not taken any vasoactive medication during the study period;
2) subjects' body temperature, heart rate (HR), systolic and diastolic blood pressures (BP) were within normal ranges.
|
| Participant flow |
First, 18 healthy right-handed adult male volunteer students were recruited by e-mail from Saitama University. We asked them to participate in face-to-face interview. A response was obtained from 14 men, of whom 12 were eligible and then enrolled in protocol A including the measurements of blood flow velocity, blood pressure and heart rate, the functional near infrared spectroscopy (fNIRS) measurement, and the ECG measurement. Two subjects were excluded as they did not meet inclusion criteria. Eventually, recruitment and enrollment of 10 participants in protocol A was conducted from October 2017 to April 2020. Thus, protocol A was completed in 10 participants
Second, 16 healthy right-handed adult male volunteer students were recruited and enrolled in protocol B for FMD measurement alone using the same criteria. Protocol B included 6 participants from protocol A. Recruitment and enrollment in protocol B was conducted from February 2018 to March 2020.
|
| Adverse events |
None |
| Outcome measures |
1) Ulnar arterial blood flow velocity
2) Hemoglobin oxygenation index, oxyhemoglobin (oxyHb), deoxyhemoglobin (deoxyHb) and total hemoglobin
3) Electrocardiogram(ECG), RRI, HF, LF/HF
4) Flow-mediated dilation(FMD) |
| Plan to share IPD |
|
| IPD sharing Plan description |
|
| Progress |
| Recruitment status |
Completed |
| Date of protocol fixation |
| 2017 |
Year |
02 |
Month |
07 |
Day |
|
| Date of IRB |
| 2017 |
Year |
10 |
Month |
24 |
Day |
|
| Anticipated trial start date |
| 2017 |
Year |
10 |
Month |
25 |
Day |
|
| Last follow-up date |
| 2021 |
Year |
07 |
Month |
11 |
Day |
|
| Date of closure to data entry |
| 2021 |
Year |
07 |
Month |
11 |
Day |
|
| Date trial data considered complete |
| 2021 |
Year |
07 |
Month |
11 |
Day |
|
| Date analysis concluded |
| 2021 |
Year |
07 |
Month |
17 |
Day |
|
UMIN-CTR Clinical Trial