Page | 003 Int. J. Environ. Res. Public Health 2016, 13, 1171 3 of 10
(Project ID: RMIT-RIF-FANGMAHMOUD). All of the participants gave written informed consent for
Int. J. Environ. Res. Public Health 2016, 13, 1171 3 of 10 the experiment.
2.2. Source of ELF-PEMF Exposure
2.2. Source of ELF-PEMF Exposure
The ELF-PEMF generation system used in this investigation was designed and is manufactured
The ELF-PEMF generation system used in this investigation was designed and is manufactured by
by MEDEC Ltd., Salter Point, Australia [28]. It has a Class II certificate (CQ041744-II) with the
MEDEC Ltd., Salter Point, Australia [28]. It has a Class II certificate (CQ041744-II) with the European European Medical Devices Directive 93/42/EEC. The ELF-PEMF generation system, which is a 1.5 m
Medical Devices Directive 93/42/EEC. The ELF-PEMF generation system, which is a 1.5 m × 0.9 m × 0.9 m rectangle sized foam mat with a plastic cover, has three pairs of different sized coils
rectangle sized foam mat with a plastic cover, has three pairs of different sized coils embedded inside
embedded inside (See Figure 1). The system has the flexibility to select different frequencies and
(See Figure 1). The system has the flexibility to select different frequencies and intensities. Our research intensities. Our research chose the ELF-PEMF fields setting for the top, middle, and bottom coils of the
chose the ELF-PEMF fields setting for the top, middle, and bottom coils of the mat to be 2.33 μT, mat to be 2.33 μT, 5.235 μT, and 6.45 μT, respectively, with a 16 Hz operating frequency. In this
5.235 μT, and 6.45 μT, respectively, with a 16 Hz operating frequency. In this setting, the effect of the setting, the effect of the electromagnetic fields for the top, middle, and bottom coils decreased at 15
electromagnetic fields for the top, middle, and bottom coils decreased at 15 cm, 30 cm, and 32 cm,
cm, 30 cm, and 32 cm, respectively. These distances were measured from the centre of each coil
respectively. These distances were measured from the centre of each coil above the mat where the
above the mat where the subject lay. The subject lies on his or her back with their body on the mat
subject lay. The subject lies on his or her back with their body on the mat and their head just off the
and their head just off the mat. The chest is over the coil with low intensity (2.33 μT), the waist lies
mat. The chest is over the coil with low intensity (2.33 μT), the waist lies over the coil with medium over the coil with medium intensity (5.235 μT), while the legs lie over the coil with higher intensity
intensity (5.235 μT), while the legs lie over the coil with higher intensity (6.45 μT). The exposure setting (6.45 μT). The exposure setting is illustrated in Figure 1. In this study, the magnetic flux density for
is illustrated in Figure 1. In this study, the magnetic flux density for the three coils was verified by the three coils was verified by direct measurement using an EFA-200 EMF analyser and external
direct measurement using an EFA-200 EMF analyser and external B-field probe with a diameter of
B-field probe with a diameter of 3 cm and a measurement accuracy of 6%. The ELF-PEMF generation
3 cm and a measurement accuracy of 6%. The ELF-PEMF generation system creates PEMF with four
system creates PEMF with four identical saw-tooth-like signal (0–100 Hz) bundles and delays, each
identical saw-tooth-like signal (0–100 Hz) bundles and delays, each lasting 20 ms. These saw-tooth-like
lasting 20 ms. These saw-tooth-like controlled signals oscillate between 0.4 V and −0.8 V.
controlled signals oscillate between 0.4 V and −0.8 V.
Figure 1. Exposure setup. The subject lies on their back on the mat with chest over Coil 1 (2.33 μT), Figure 1. Exposure setup. The subject lies on their back on the mat with chest over Coil 1 (2.33 μT),
waist over Coil 2 (5.235 μT), and legs over Coil 3 (6.45 μT). waist over Coil 2 (5.235 μT), and legs over Coil 3 (6.45 μT).
2.3. ECG Equipment
2.3. ECG Equipment
ECG is a vital human physiological signal that can be used to diagnose the condition of the heart.
ECG is a vital human physiological signal that can be used to diagnose the condition of the
The ECG time intervals, such as PR, RT, QT, and RR, are the main propagation characteristics that relate
heart. The ECG time intervals, such as PR, RT, QT, and RR, are the main propagation characteristics
directly to phases of the cardiac electric conduction. The P-wave is caused by atrial depolarisation, and
that relate directly to phases of the cardiac electric conduction. The P-wave is caused by atrial
its typical duration is normally less than 0.12 s. The PR interval is the portion of ECG wave from the
depolarisation, and its typical duration is normally less than 0.12 s. The PR interval is the portion of
start of P-wave (onset of atrial depolarisation) to the beginning of QRS-complex (onset of ventricular
ECG wave from the start of P-wave (onset of atrial depolarisation) to the beginning of QRS-complex
depolarisation). Its duration is normally 0.12 to 0.20 s. The RR interval is the duration between two
(onset of ventricular depolarisation). Its duration is normally 0.12 to 0.20 s. The RR interval is the
adjacent R waves, which is the reciprocal of the heart rate. The prominent QRS complex is caused by
duration between two adjacent R waves, which is the reciprocal of the heart rate. The prominent
the ventricle depolarisation and has a typical duration of 0.06 to 0.10 s. Within the period of the ELF
QRS complex is caused by the ventricle depolarisation and has a typical duration of 0.06 to 0.10 s.
range, those ECG time intervals have high diagnostic values for various cardiovascular diseases.
Within the period of the ELF range, those ECG time intervals have high diagnostic values for various
Lead-I ECG electrodes were connected to the BIOPAC systems (ECG Module). The ECG module
cardiovascular diseases.
consists of an instrumentation amplifier (IA) and a 50 Hz notch filter. The IA has a very high unwanted
Lead-I ECG electrodes were connected to the BIOPAC systems (ECG Module). The ECG
signal rejection capability and a variable gain (the gain was set to 1000). The sampling rate for ECG
module consists of an instrumentation amplifier (IA) and a 50 Hz notch filter. The IA has a very high
was set to 1000 samples/s. Lead-I ECG is the voltage between the left arm (LA) electrode (positive) and
unwanted signal rejection capability and a variable gain (the gain was set to 1000). The sampling rate
right arm (RA) electrode and is one of the three bipolar leads. Lead-I ECG provides a left lateral view
for ECG was set to 1000 samples/s. Lead-I ECG is the voltage between the left arm (LA) electrode
of the heart. Though Leads I, II, and III are often used simultaneously to monitor multiple regions of
(positive) and right arm (RA) electrode and is one of the three bipolar leads. Lead-I ECG provides a
the heart, we chose Lead I for this study because it is most often used for cardiac monitoring. Moreover,
left lateral view of the heart. Though Leads I, II, and III are often used simultaneously to monitor multiple regions of the heart, we chose Lead I for this study because it is most often used for cardiac monitoring. Moreover, we are interested in comparing the time intervals of ECG. Leads I, II, and III will provide the same information in this regard. The ECG data was recorded with AcqKnowledge software (v.3.7.1, BIOPAC Systems, Inc., Goleta, CA, USA) in ASCII text files and processed by
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