Relaxation is becoming increasingly important in modern stressful times. Besides special psychological practices or consuming pharmaceuticals, one can achieve a more relaxed state also by applying an appropriate magnetic field stimulation of the head (low-intensity rTMS). Following the entrain-ment model, we did the research using carefully chosen frequencies of modest MF intensity that followed the principles of clinical trials. Besides the situations of blind verum stimulation and the sham one, we tested also the situation that included expectations of the applied stimulation. The testing was done by electrophysiological methods and VAS. The results demonstrated an objective relaxing effect of MF stimulation, where drowsiness was not stimulated. This outcome is much more evident from electrophysiological data than from the VAS ones. From the latter results, we noticed even a slightly negative reaction to expectations.
There are many different non-invasive methods of how to achieve a relatively satisfying relaxed state that is increasingly needed in our stressful times. Some of them are based on psychological methods, like Shultz’s autogenic training including progressive reduction of muscle tension; others on special practices, like meditation or (self) hypnosis. The state of relaxation is a state devoid of tension and anxiety; the deeper the relaxation the lesser tension and anxiety. Relaxation, therefore, brings calmness and diminishes the level of stress hormones like adrenaline and cortisol [
In modern times, however, one may need a deep relaxation, when he/she is not in a position to perform any relaxation practice, while, for instance, driving a car. In such a situation, it would be utterly inadvisable to take medication for deep relaxation in the form of an anxiolytic pill. The latter may have long and undesired negative side effects like drowsiness, as well as slower and less coordinated reactions. A completely different method should be used in such cases, the one that would enable one to simultaneously perform a task without drowsiness and with no mentioned negative side effects. One such possibility is to use pulsed magnetic stimulation (PEMF) in the region of the head.
Magnetic stimulation of the head region is known also under the name repetitive transcranial magnetic stimulation (rTMS). Usually, it uses relatively high intensities of magnetic fields of low frequencies. There are many positive reports concerning this treatment. A comprehensive study published as a review article concludes that although the interpretation of the results is difficult because of different treatment protocols and the lack of a placebo-controlled design in the majority of studies, there is evidence for anxiolytic action of rTMS [
Besides reports concerning high-intensity rTMS that have clear physiological effects through magnetic induction of electric fields, some studies claim also biological influences of MF stimulation of low intensities. The latter cannot evoke action potentials; neither do they have thermal effects. Therefore, lacking a general theory of bioelectromagnetics, the mechanism of their bioeffects is still an object of scientific debate. Various models are proposed, some of them with empirical confirmations; nevertheless, no one has been universally recognized (see also [
When we come to a possibility of influencing relaxation, we may assume the incidental magnetic stimulation will enhance the proportion of brainwaves that are in resonance with the frequency of the stimulating magnetic field (MF). This may not necessarily mean only the same frequency matching but may entail also relations between a frequency and its subharmonics or its higher harmonics. The principle, where an exogenous vibration (not necessarily electromagnetic by nature, see also [
An interesting study was performed by Ghione and colleagues [
Since there is a controversy concerning the EEG measurements and entrainment expectations, we intended to check what is the effect of a transcranial low-intensity MF stimulation following the entrainment model on various physiological parameters and self-perception of volunteers, in addition to examine only brainwaves. As evident from the previous subchapter for the targeted physiological state, we chose relaxation since it is relatively easy to identify it using electrophysiological and brainwave measurements. Having learned that even subharmonics may have an important influence on brainwaves, we chose two frequencies: a leading one from the alpha region that should be in direct resonance with the targeted brainwave enhancement and a supporting one of a lesser intensity representing a subharmonic from the high delta region (see also
・ Brainwaves: Enhancing the proportion of alpha and delta waves during stimulation, sleep should not be induced;
・ General electrophysiological parameters: Enhancing the parasympathetic activity, although Ghione et al. [
・ Self-perception: Identification of a more relaxed state.
In the research we wanted to check also the influence of expectation in combination with MF stimulation on all three above listed groups of parameters, so in addition to the sham-exposed volunteers (control) and the stimulated ones (verum), we examined parameters of volunteers who 1) were stimulated, 2) knew that they were stimulated and 3) were told what should they expect from the stimulation―the informed situation. Our hypothesis here was that the intentionally provoked expectations in the anticipated direction (relaxation) would enhance the influence of MF stimulation.
Although the majority of research in bioelectromagnetics is performed by using a homogenous MF, such field is only very rarely applied in practical situations where an MF stimulation may have some practical or therapeutic use. Namely, on the market devices producing highly non-homogenous MFs are mostly offered, which shaped our decision to apply a highly inhomogeneous field to volunteers. The MF was produced by five different coils arranged around the head (see
Frequency (Hz) | Magnetic field intensity (B) | Location | Role |
---|---|---|---|
10.12 | 2.5 mT | occiput (1 coil) | direct entrainment frequency |
3.375 | 0.25 mT | occiput (1 coil), temporal lobes: left (2 coils) and right (2 coils) | supportive subharmonic frequency |
The research was performed in May 2019 in the laboratories of the Institute for Bioelectromagnetics and New Biology (BION Institute) in Ljubljana, Slovenia, EU. In the research, 25 volunteers aged from 29 to 76 years (13 women and 12 men) were subject to three different experimental situations:
1) Double blind sham stimulation (Control situation),
2) Double blind true stimulation (Verum situation),
3) Informed true stimulation as explained in the Introduction (Informed situation).
In the first two situations, the volunteers were treated in conformity with the clinical trials conditions:
・ Prospectiveness (general criteria for the effectiveness of the device’s activity were determined in advance);
・ Placebo effect ruled out (volunteers did not know whether they were stimulated or not);
・ Double blind (neither the volunteer nor the research assistant knew whether MF stimulation was applied or not);
・ Randomized (the decisions about sham or true exposure were made randomly).
The volunteers in the Informed situation were intentionally informed about the stimulation; the situation was always applied after the Control and the Verum situations since the volunteers were the same in all three situations.
The volunteers signed an informed consent in which they agreed to cooperate as subjects in this non-invasive scientific research in bioelectromagnetics.
We applied MF stimulation in the region of the head as can be seen in
During the research, we constantly measured the environmental EM fields and found no significant variation in the frequency range from 5 Hz to 2 GHz between different days. The geomagnetic field varied from 47,946 to 48,003 nT (data from the nearest INTERMAGNET [
Each volunteer attended the measurements thrice at the same hour of the day. At the arrival, he/she filled out the questionnaire and completed the visual analog scale (VAS) test (see chapter 2.2 for more detail). After that research assistant placed the device on his/her head in an appropriate position (
With every volunteer, we calculated thirty-second medians for the whole measurement period. Based on these data, we calculated aggregated thirty-second medians for all 25 volunteers and used this data to draw graphs for each measured parameter and further statistical analysis. For the sake of analysis and interpretation of the results, 30 minutes of measurements were split into three parts (each consisting of 20 data points with calculated 30-second median):
・ first part―from 0 to 10 minutes,
・ second part―from 10 to 20 minutes,
・ third part―from 20 to 30 minutes.
For calculating statistically significant differences between any of the three experimental situations, we used the Friedman test. With a post-hoc test (Wilcoxon Signed-Rank test) we determined which comparison demonstrated these differences. The outcome of the results for all tests was corrected by the Holm-Bonferroni correction for multiple comparisons [
The Visual Analogue Scale (VAS) has been in use for the measurement of subjective parameters that are impossible to measure by any physical method, like pain, anxiety, quality of sleep, etc. since the 1920s [
We used the VAS scale for evaluation of the subjective perception of five different parameters: relaxation, energy level, tension, concentration, and fatigue/tiredness. VAS scale was included in online survey volunteers completed before and after each measurement. The online open-source application for web surveys [
Besides VAS testing, a question as to when a volunteer expected to be under the true stimulation as well as when they felt better was asked after the second testing (
Results concerning electrophysiological measurements demonstrate statistically significant differences between three experimental situations for the following parameters: skin conductance, respiration rate, heart rate, the proportion of beta, alpha, theta, and delta waves and thorax expansion depth (
A post-hoc test (see
Parameter | Question | Anchor descriptors |
---|---|---|
Relaxation | How relaxed do you feel at the moment? | Very unrelaxed―very relaxed |
Energy | How full of energy do you feel at the moment? | Complete lack of energy―full of energy |
Concentration | How focused do you feel at the moment? | Very unfocused―very focused |
Fatigue/ tiredness | How tired do you feel at the moment? | Not tired―very tired |
Tension | How tense do you feel at the moment? | Very tense―not tense |
0 - 10 min | 10 - 20 min | 20 - 30 min | |
---|---|---|---|
SC | 0.000 | 0.000 | 0.000 |
RR | 1.000 | 0.024 | 1.000 |
HR | 0.000 | 0.000 | 0.000 |
TMP | 1.000 | 1.000 | 0.056 |
beta | 0.000 | 0.000 | 0.000 |
alpha | 1.000 | 0.000 | 1.000 |
theta | 0.024 | 1.000 | 1.000 |
delta | 0.003 | 0.000 | 0.000 |
HRV | 0.949 | 1.000 | 1.000 |
TED | 0.268 | 0.000 | 0.000 |
0 - 10 min | 10 - 20 min | 20 - 30 min | ||||||||
---|---|---|---|---|---|---|---|---|---|---|
comparison pair | Verum | Informed | Verum | Verum | Informed | Verum | Verum | Informed | Verum | |
Control | Control | Informed | Control | Control | Informed | Control | Control | Informed | ||
SC | 0.008 | 0.017 | 1.000 | 0.008 | 0.128 | 0.008 | 0.008 | 1.000 | 0.008 | |
RR | 1.000 | 1.000 | 1.000 | 0.227 | 1.000 | 0.070 | 1.000 | 1.000 | 1.000 | |
HR | 0.008 | 0.008 | 1.000 | 0.010 | 0.008 | 0.078 | 0.008 | 0.011 | 1.000 | |
TMP | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 0.747 | 1.000 | 0.687 | |
beta | 0.008 | 0.008 | 0.631 | 0.008 | 0.008 | 0.036 | 0.008 | 0.008 | 1.000 | |
alfa | 1.000 | 1.000 | 1.000 | 0.009 | 0.008 | 1.000 | 1.000 | 1.000 | 1.000 | |
theta | 0.022 | 1.000 | 0.128 | 0.579 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | |
delta | 0.878 | 0.010 | 1.000 | 0.008 | 0.008 | 1.000 | 0.025 | 0.028 | 1.000 | |
HRV | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | |
TED | 0.246 | 0.227 | 1.000 | 0.008 | 0.747 | 0.530 | 0.022 | 0.032 | 1.000 | |
Skin conductance was lower for the Verum situation than for the Control one during the entire measurements while it was lower only during the first 15 minutes for the Informed situation (
Relative thorax expansion difference was in many ways similar to skin conductance. Again, values for the Verum situation were lower when compared to the Control for most of the measurements (
Heart rate was lower for both the Verum and the Informed situations than for the Control during most of the measurements (
The proportion of alpha waves demonstrated statistically significant differences from the Control situation for both the Verum and the Informed situations only in the second part of the measurements (
more long-lived. Higher alpha waves for the Verum and the Informed situations indicate slightly increased relaxation. Expectation does not seem to have any effect on brainwaves for the alpha spectra as both the Verum and Informed situations followed very similar courses.
Opposite to the proportion of alpha waves, the beta ones demonstrated significant differences from the Control with both the Verum and the Informed situations during the whole length of measurements (
Opposite to the proportion of beta waves, the theta ones demonstrated significant differences between the Verum and the Control situation only in the first part of measurements (
After surveying all VAS measurements, we estimated that only the scores from 20 volunteers were suitable for analysis. Results from five volunteers were excluded due to high initial VAS scores, which did not allow a reliable evaluation of changes during the treatments. Compared to their initial state, volunteers felt more relaxed, energized and focused, and less fatigued and tense after the measurements within any test situations (
0 - 10 min | 10 - 20 min | 20 - 30 min | |||||||
---|---|---|---|---|---|---|---|---|---|
Verum | Informed | Control | Verum | Informed | Control | Verum | Informed | Control | |
SC | 16.732 ± 0.145 | 14.251 ± 0.372 | 20.63 ± 0.217 | 15.129 ± 0.233 | 14.528 ± 0.26 | 20.131 ± 0.086 | 14.704 ± 0.153 | 12.157 ± 0.163 | 20.175 ± 0.186 |
RR | 17.688 ± 0.108 | 17.239 ± 0.121 | 17.552 ± 0.155 | 17.098 ± 0.094 | 16.511 ± 0.172 | 17.183 ± 0.121 | 16.615 ± 0.121 | 16.176 ± 0.175 | 16.704 ± 0.173 |
HR | 72.012 ± 0.186 | 70.778 ± 0.296 | 73.13 ± 0.248 | 71.691 ± 0.176 | 71.668 ± 0.277 | 73.639 ± 0.317 | 70.263 ± 0.228 | 71.39 ± 0.314 | 72.916 ± 0.342 |
TMP | 34.781 ± 0.084 | 34.959 ± 0.041 | 34.447 ± 0.046 | 35.03 ± 0.031 | 35.078 ± 0.018 | 34.583 ± 0.032 | 34.851 ± 0.02 | 35.035 ± 0.022 | 34.735 ± 0.019 |
beta | 25.607 ± 0.326 | 25.644 ± 0.324 | 25.585 ± 0.324 | 26.797 ± 0.344 | 26.74 ± 0.343 | 27.01 ± 0.357 | 25.396 ± 0.587 | 25.314 ± 0.565 | 25.316 ± 0.57 |
alpha | 21.267 ± 0.306 | 21.306 ± 0.303 | 21.397 ± 0.295 | 20.694 ± 0.271 | 20.804 ± 0.275 | 20.925 ± 0.245 | 19.53 ± 0.25 | 19.583 ± 0.25 | 19.495 ± 0.219 |
theta | 23.052 ± 0.149 | 23.07 ± 0.15 | 23.184 ± 0.15 | 23.283 ± 0.173 | 23.304 ± 0.173 | 23.262 ± 0.176 | 24.435 ± 0.256 | 24.489 ± 0.242 | 24.432 ± 0.24 |
delta | 30.073 ± 0.321 | 29.98 ± 0.31 | 29.834 ± 0.297 | 29.226 ± 0.344 | 29.152 ± 0.345 | 28.802 ± 0.254 | 30.639 ± 0.346 | 30.614 ± 0.339 | 30.756 ± 0.313 |
HRV | 10.808 ± 0.436 | 10.844 ± 0.348 | 11.57 ± 0.56 | 12.889 ± 0.373 | 12.42 ± 0.372 | 11.826 ± 0.4 | 12.594 ± 0.68 | 12.075 ± 0.499 | 13.431 ± 0.488 |
TED | 2.678 ± 0.043 | 2.51 ± 0.045 | 3.681 ± 0.108 | 2.828 ± 0.08 | 2.797 ± 0.124 | 3.33 ± 0.139 | 3.05 ± 0.109 | 2.92 ± 0.157 | 2.919 ± 0.104 |
VAS parameter | p-value (paired t-test) | p-value corrected after Holm-Bonferroni correction |
---|---|---|
Relaxation | 0.770 | 1.000 |
Energy level | 0.018* | 0.090 |
Concentration | 0.598 | 1.000 |
Fatigue/tiredness | 0.795 | 1.000 |
Tension | 0.434 | 1.000 |
After completed Control and Verum situations, volunteers were asked to evaluate which measurements made them feel more relaxed. As the research was double-blind and randomized, the possible answers were (A) today’s measurement made me feel more relaxed, (B) the previous measurement made me feel more relaxed, (C) both were equally relaxing, (D) I haven’t noticed any differences. Results showed that 56% of volunteers felt more relaxed after the Verum, and 28% after the Control situation (
If we take the results of physiological measurements first, we may observe some discrepancies between the parameters concerning the working of the autonomic nervous system and brainwaves. Namely, while the parameters SC, HR, and TED for Verum and Informed situations demonstrate that the physiological balance inclines towards parasympathetic stimulation, which conforms to relaxation, the beta waves demonstrate a rise of the median amplitude, which indicates a more attentive state. A significant rise of beta waves during stimulation together with enhancing the alpha waves (at least in the middle period) is a surprise that demands further consideration and research. Enhancing the attentive state is corroborated also by a diminution of theta and delta waves, significantly with the Verum situation. And as already addressed, it is interesting that at least in the middle period (10 - 20 min) the median power of alpha waves also increased.
These apparently contradictory results may be interpreted in the sense that the deep effect on the vegetative nervous system of the MF stimulation exhibits the expected calming or anti-stress effect in conformity with the entrainment model expectation. However, it did not convey more sleepiness, but even more vigilance and diminished tendency to fall into sleep. Thinking in terms of usability of such stimulation, it seems it could be very applicable to situations that demand vigilance (like driving a car) and may at the same time tend to provoke stress.
From the results we may also see that all statistically significant results of Verum and Informed situations are of the same sign and very similar; the differences (vs. Control) with the Verum situation tend to be a little more pronounced than with the Informed one. This indicates that acquainting volunteers with the expected influence did not enhance the physiological response, but worked even slightly inhibitory, like a nocebo, which may be seen especially in the results of skin conductance. This difference, small as it is, again corroborates the objective influence of the stimulation regime.
Regarding the VAS testing results, they are not prominent, though there was a tendency to feel a lesser energy level after the Verum stimulation vs. Control. We interpret this in the sense that the volunteers associated a more relaxed and less tense state as the one of a lower energy level, in conformity with the perception of a higher energy level when the concentration of adrenaline in the blood increases. Also worthy of consideration is the direct response of volunteers that in the majority correctly distinguished the difference between Verum and Control and the fact that a significant proportion of volunteers recognized the Verum stimulation as more pleasant.
The discrepancy between the results of electrophysiological and VAS measurement may reflect two circumstances. The first concerns our long experience that there is a huge hiatus between registrations of deep subconscious levels (autonomous nervous system) and consciousness. Accordingly, subtle influences that are registered by the autonomic nervous system remain largely unregistered on the level of normal waking consciousness; and VAS concerns the latter. The second tackles VAS itself. Namely, it is normally used in situations, where it is very clear, what the measured parameter means, like for instance pain. It has a special meaning for volunteers since it tackles one of their most prominent problems. In our testing, the volunteers did not have a general issue to be cured or ameliorated. On average, they did not have a clear relation towards any of the five parameters and therefore they might have not succeeded to connect subtle differences that may have appeared in their minds to VAS questions. In the future, researches concerning MF stimulation, one should try to find parameters that may have a clearer meaning for an average volunteer.
A slight negative (nocebo) effect observed with some physiological and VAS parameters may be interpreted as a psychological reaction of volunteers to expectations. According to our assumption it tackles the psychological level of volunteers and tells that expectancy of relaxation can hinder objective stimulatory effects of the pulsed MF.
・ A much higher number of statistical differences (after Holm-Bonferroni corrections) between either Verum and Control or Informed and Control in comparison to Verum vs. Informed strongly confirm the objective effect of the stimulating field of the device.
・ The expectation that the autonomous nervous system will be stimulated in the parasympathetic direction was also confirmed (especially SC and HR parameters).
・ The expected entrainment in alpha waves was only partially confirmed since it showed itself only in the middle period of both situations involving MF stimulation.
・ The hypothesis that the passage to sleep will not be stimulated was also confirmed.
・ Relatively small differences between Verum and Informed situations speak that
² they felt better after it,
² the stimulating magnetic field effect on human physiology is much stronger than psychological influences based on expectancies.
・ It seems that in this research situation expecting relaxation brings a measure of stress, which was reflected in a frequent lowering of Informed values in comparison to the Verum ones.
・ From VAS and queries after testing, we may conclude that
² the volunteers predominantly recognized the true stimulation and
² they felt better after it.
・ Much stronger results (statistically regarded and in the magnitude of differences) in the physiological part of the research than VAS and queries confirm our already known experiences that physiology is a much better detector of various fields’ influences than psychology (awareness).
The future research on this line should include
・ duration of the physiological changes after the end of stimulation,
・ some other combinations of frequencies regarding optimization of entrainment,
・ inclusion of a positive control into research,
・ research of pure placebo (no stimulation, but informed as if stimulated) influence,
・ optimization of VAS testing,
・ researching the best intensity windows for stimulating relaxation in the direction of lower intensities.
This work was supported by MDCN Technologies Inc. New York, USA. and MDCN Tech Ltd. Slovenia, EU. We would like to thank Vesna Periček Krapež and Mateja Senica for reviewing and correcting the manuscript.
The authors declare no conflicts of interest regarding the publication of this paper.
Jerman, I., Dovč, P. and Ratajc, P. (2019) Influencing Relaxation by a Low Intensity Transcranial Pulsed Magnetic Stimulation Applying the Entrainment Model. Open Access Library Journal, 6: e5741. https://doi.org/10.4236/oalib.1105741