PULSED MAGNETIC FIELD THERAPY - HOW DOES IT WORK ?

An extract taken from a lecture delivered on 28th January, 1995

by Dr. D. C. LAYCOCK

All living cells within the body possess potentials between the inner and outer membrane of the cell, which, under normal healthy circumstances, are fixed. Different cells, e.g. Muscle cells and Nerve cells, have different potentials of about -70 milli-Volts respectively. When cells are damaged, these potentials change such that the balance across the membrane changes, causing the attraction of positive sodium ions into the cell and negative trace elements and proteins out of the cell. The net result is that liquid is attracted into the interstitial area and swelling or oedema ensues. The application of pulsed magnetic fields has, through research findings, been shown to help the body to restore normal potentials at an accelerated rate, thus aiding the healing of most wounds and reducing swelling faster. The most effective frequencies found by researchers so far, are very low frequency pulses of a 50Hz base. These, if gradually increased to 25 pulses per second for time periods of 600 seconds (10 minutes), condition the damaged tissue to aid the natural healing process.

Pain reduction is another area in which pulsed electromagnetic therapy has been shown to be very effective. Pain signals are transmitted along nerve cells to pre-synaptic terminals. At these terminals, channels in the cell alter due to a movement of ions. The membrane potential changes, causing the release of a chemical transmitter from a synaptic vesicle contained within the membrane. The pain signal is chemically transferred across the synaptic gap to chemical receptors on the post synaptic nerve cell. This all happens in about one 2000th of a second, as the synaptic gap is only 20 to 50 nanometres wide (1 nanometre = 1/1000,000,000 of a metre). As the pain signal, in chemical form, approaches the post synaptic cell, the membrane changes and the signal is transferred. If we look at the voltages across the synaptic membrane then, under no pain conditions, the level is about -70 milli-Volts. When the pain signal approaches, the membrane potential increases to approximately +30 milli-Volts, allowing a sodium flow. This in turn triggers the synaptic vesicle to release the chemical transmitter and so transfer the pain signal across the synaptic gap or cleft. After the transmission, the voltage reduces back to its normal quiescent level until the next pain signal arrives.

The application of pulsed magnetism to painful sites causes the membrane to be lowered to a hyper-polarisation level of about -90 milli-Volts. When a pain signal is detected, the voltage must now be raised to a relatively higher level in order to fire the synaptic vesicles.

Since the average change of potential required to reach the trigger voltage of nearly +30 milli-Volts is +100 milli-Volts, the required change is too great and only +10 milli-Volts is attained. This voltage is generally too low to cause the synaptic vesicle to release the chemical transmitter and hence the pain signal is blocked. The most effective frequencies that have been observed from research in order to cause the above changes to membrane potentials, are a base frequency of 200Hz and pulse rate settings of between 5 and 25Hz.

Using Pulsed Magnetic Therapy and Phototherapy
Applications and Research
Notes for users - November 2005

Pulsed Magnetic Therapy Using Specific Frequencies :

Magnetic field can be made to pulse at different rates.

Conditions can be frequency specific.

Base rate commonly 50Hz or 200Hz.

Pulse rate varies and is set based on research.

PMF Effect on Fracture Repair
Base 50Hz:

Constant pulse.

Duration 20min + Repeat 4 hourly.

Non-union fractures - treat proximal segment as well as fracture site.

PMF can Mimic Initial Phase of Fresh Fracture Repair.
Calcification of fibro cartilage
Vascular invasion
Production of bone marrow and proliferation of bone cells

Bone ossification:

Collagen production in bone marrow is promoted
Expression of bone morphogenetic proteins is facilitated.

PMF Aids Nerve Growth and Repair:

Establishes currents of injury and so accelerates fracture union Improves formation of neurites by up to 30%

Aids improvement in spinal deficit.

Pain Control :
Best effect using base of 200Hz, with constant pulse for acute stage.

Use at 5 pulses per sec for chronic pain.

Treatment repeated every 4 hrs for 10 min.

Other Conditions :

Arthritis – treat as for bone repair.

Osteoporosis – 50Hz constant for as long and often as possible.

Joint injuries – 50Hz at 17.5 to reduce oedema

Bruising and early injuries – 50Hz at 5 pulses/sec

Research – Veterinary Conditions shown to improve include:

Traumatic periostitis, symptom free achieved after 3 weeks
Disuse osteoporosis
Muscle tone improves and spinal deficit is reduced

Modes of Action
This is at the cellular level:

It can influence the structure of the cellular membrane.

It can influence the movement of ions and charged particles.

Suggestion is that PMF has hormone like influence on ATP production.

PMF Effect on Cellular Membrane
Re-establishes normal ionic flow
As a result this :

· Reduces oedema

· Enhances wound repair

· Aids re-vascularisation of damaged tissues.

Effect on the Process of Replication of Cells and Proteins
It has an affect on DNA synthesis, enhancing the processes of transcription and translation.

This enhances the formation of new cells and cellular components.

Effects of Pulsed Magnetism on Protein Synthesis:
PMF can promote DNA synthesis and cell proliferation
PMF stimulates mRNA expression of bone morphogenetic proteins
PMF upregulates bone morphogenetic proteins 2 and 4mRNA

Summary -Practical Applications in Physiotherapy
Apply at a base of 50Hz for joint injuries, bruises, muscle problems, tendon injuries and fractures.

Apply at a base of 200Hz for pain control

SAFETY

Pulsed magnetic therapy is safe to be used by the client under direction of the physiotherapist.