
Frequency, measured in Hertz (Hz), is a fundamental concept in Pulsed Electromagnetic Field (PEMF) therapy, representing the number of cycles a wave completes per second. However, the term “frequency” in PEMF often encompasses a broader meaning, relating to the pulsing of the electromagnetic field. Understanding this distinction and the different aspects of frequency is crucial for both grasping how PEMF works and choosing an appropriate device.
Pulses vs. Frequencies: Unpacking the Core Concepts
While technically referring to the wave cycle rate, “frequency” in PEMF parlance often describes the rate of change of the pulse, or how often the magnetic field is switched on and off. This “pulsing” is the defining characteristic of PEMF and differentiates it from static magnetic fields (Pilla, 2013). The constant change of intensity creates motion, which induces the movement of ions and electrolytes, in turn stimulating the cell membrane, and ultimately leading to the positive effects of PEMF therapy (Adey, 1993). This is also the reason intensities are kept relatively lower in PEMF therapy.
Carrier Frequencies and Waveforms: The Foundation of PEMF Signals
A pure, unmodulated electromagnetic field isn’t typically used in PEMF. Instead, a carrier frequency is employed, often in the Extremely Low Frequency (ELF) range or higher, typically below 10,000 Hz. This carrier frequency is then modulated, meaning its amplitude or other characteristics are varied according to a specific waveform (Bassett, 1989).
Here are the common waveform varieties used in PEMF:
- Sine Wave: The most common waveform, sine waves create smooth, gradual changes in the magnetic field. Research has shown their effectiveness in bone healing, particularly in early bone growth stimulators (Bassett et al., 1982). Most PEMF devices that are able to create higher intensities, typically employ sine waves for their stimulation pattern.
- Square Wave: This waveform involves abrupt on-off transitions, creating rapid changes in the magnetic field. While commonly used in higher intensity PEMF systems, whether or not the use of square wave patterns provides any additional health benefits beyond that of sine waves is still being investigated (Markov, 2007).
- Sawtooth Wave: This waveform features a gradual rise followed by a sudden drop, or vice versa. These are found more often in lower intensity devices. While some clinical data exists, more research is needed to confirm its benefits.
- Custom Waveforms: Some devices utilize proprietary waveforms, designed with specific therapeutic goals in mind. These custom waveforms are often based on extensive research and development, aiming to optimize the biological effects of the PEMF signal.
Harmonics: The Unseen Frequencies
An important aspect of PEMF signals, especially those using square or sawtooth waves, is the presence of harmonics. Harmonics are multiples of the fundamental frequency. For example, a 10 Hz square wave will also produce harmonics at 20 Hz, 30 Hz, 40 Hz, and so on, although typically only the odd harmonics, with frequencies of 30 Hz, 50 Hz, 70 Hz and so on are present.
These harmonics can extend into very high-frequency ranges, even if the fundamental frequency is low. This is because the sharp transitions in these waveforms contain a wide spectrum of frequencies. While the intensity of these harmonics is usually much lower than the fundamental frequency, their presence should be considered, especially when using high-intensity PEMF devices, since even the most effective PEMF devices use very low intensities. More is not necessarily better.
The biological effects of harmonics are not yet fully understood. Some researchers believe they may contribute to the overall therapeutic effect, while others caution that they could potentially have unwanted effects. More research is needed to clarify the role of harmonics in PEMF therapy. It is always recommended to use the lowest possible intensity for the shortest amount of time to get the maximum benefits from PEMF therapy.
The Importance of Pulse Packages: Bursts of Therapeutic Energy
Many PEMF systems, especially those using lower frequencies, deliver the electromagnetic field in “pulse packages” or “bursts.” This means that instead of a continuous stream of pulses, the pulses are grouped together with gaps in between. These gaps can be longer than the bursts themselves.
For example, a 2 Hz pulse package might consist of a short burst of pulses delivered at a higher frequency (e.g., 100 Hz) repeated twice per second. This approach is believed to be more biologically effective than continuous pulses at the same low frequency because it mimics natural biorhythms and allows for cellular “rest” periods (Pilla, 2013).
Frequency Range and Specificity: Tailoring the Signal to the Need
Different frequency ranges are associated with different therapeutic effects:
- Low Frequencies (1-50 Hz): Often used for bone healing, relaxation, and sleep improvement. Devices focusing on these benefits should offer a range of low frequencies (McLeod & Rubin, 1992).
- High Frequencies (50 Hz and above): May be more effective for pain relief, inflammation reduction, and circulation enhancement (Vallbona et al., 1996).
Most PEMF systems have frequencies below 500 Hz, and higher frequencies are thought by many to be unnecessary, and potentially less safe.
Resonance: Tuning into Cellular Frequencies

Within these frequency ranges, the concept of resonance may play a significant role. Resonance occurs when an object is exposed to a frequency that matches its natural frequency, causing it to vibrate more intensely. Think of pushing a child on a swing: if you push at the right time (matching the swing’s natural frequency), the swing goes higher with less effort. Similarly, specific frequencies may resonate with certain cellular structures or processes, potentially amplifying the therapeutic effects. For instance, certain frequencies might resonate with cell membrane receptors, enhancing their responsiveness to the PEMF signal, and leading to more efficient cellular communication and repair. While the exact resonant frequencies of different cellular components are still being researched, the principle suggests that using frequencies that resonate with the target tissue or process could enhance the efficacy of PEMF therapy.
Key Considerations Based on Frequency and Pulses
When selecting a PEMF device, consider the following:
- Frequency Range: Does it offer the frequencies relevant to your needs?
- Pulse Characteristics: Does it use pulse packages or continuous pulses? Are the pulse patterns adjustable?
- Carrier Waveform: What type of waveform does it employ (sine, square, sawtooth, or custom)?
- Harmonics: Is the device designed to minimize unwanted harmonics, particularly if it uses higher intensities? This information may not always be readily available from manufacturers but can be inferred from the waveform and intensity characteristics.
- Intensity Control: Can you adjust the intensity independently of the frequency? This is important because lower intensities are generally recommended when using higher frequencies.
- Scientific Evidence: Does the manufacturer provide information about the research supporting their chosen frequencies and pulse patterns?
Demystifying Frequency
Understanding the nuances of frequency, pulses, carrier waves, waveforms, and harmonics in PEMF therapy is crucial for making informed decisions. By considering these factors, you can choose a device that aligns with your specific needs and maximizes the potential benefits of this powerful technology. Remember that the ideal PEMF device is one that offers a range of frequencies, flexible pulse settings, a solid foundation in scientific research, and a design that minimizes potentially unwanted harmonics while maximizing therapeutic efficacy.
References
- Adey, W. R. (1993). Biological effects of electromagnetic fields. Journal of Cellular Biochemistry, 51(4), 410-416.
- Bassett, C. A. (1989). Fundamental and practical aspects of therapeutic uses of pulsed electromagnetic fields (PEMFs). Critical Reviews in Biomedical Engineering, 17(5), 451-529.
- Bassett, C. A., Mitchell, S. N., & Gaston, S. R. (1982). Pulsing electromagnetic field treatment in ununited fractures and failed arthrodeses. JAMA, 247(5), 623-628.
- Markov, M. S. (2007). Pulsed electromagnetic field therapy history, state of the art and future. The Environmentalist, 27(4), 465-475.
- McLeod, K. J., & Rubin, C. T. (1992). The effect of low-frequency electrical fields on osteogenesis. Journal of Bone and Joint Surgery. American Volume, 74(6), 920-929.
- Pilla, A. A. (2013). Electromagnetic fields instantaneously modulate nitric oxide signaling in challenged biological systems. Biochemical and Biophysical Research Communications, 436(4), 608-613.
- Vallbona, C., Hazelwood, C. F., & Jurida, G. (1996). Response of pain to static magnetic fields in postpolio patients: a double-blind pilot study. Archives of Physical Medicine and Rehabilitation, 78(11), 1200-1203.