In this article, we take a look at how electrical stimulation can help with pain management. Pain that we meet in rehabilitation is often complicated and difficult to deal with. For a start, pain can have both emotional and mental components in addition to its physical aspect. Pain is a complex and subjective experience that involves not only the physical sensation of discomfort or distress but also emotional and cognitive elements. Having said that people need to deal with it as effectively and safely as possible.

Electrical stimulation is a popular drug-free treatment method for various applications, including the physical management of pain. It is commonly thought of as "TENS", which is short for "Transcutaneous Electrical Nerve Stimulation", and involves the use of a product which delivers low-energy electrical currents through electrodes placed on the skin's surface. As we will learn, there are actually a wide number of approaches for pain management using electrical stimulation, and even TENS is not one specific method.

A quick web search for TENS will bring up many inexpensive consumer products that promise to help relieve pain. Most will not be approved medical devices, and often, their specifications are not clearly expressed. Users may find relief with these commonly available devices but often may not.

The origin and severity of the pain will influence the effectiveness of this treatment. Professional use devices will typically allow more control over the types of stimulation and, as we will see, can adapt what they deliver to treat different forms of pain.

While some techniques may only provide temporary relief, their benefits still often outweigh the drawbacks as the risks of application are few. As with any treatment, contraindications and indications should be considered. The safety and efficacy of electrical stimulation are typically assessed against other potential alternatives. We believe that given its relative safety and non-invasive nature, electrical stimulation should be a go-to option before resorting to more invasive methods.

As we mentioned above, there's a common misconception that applications for pain relief are all about a single homogeneous approach called TENS. However, there are a variety of methods that can be tailored to the type and origin of the pain. "TENS" (Transcutaneous Electrical Nerve Stimulation), is just one of the many protocols available. As we will see it is not even one 'exact' protocol.

This raises an important point. There is a need to clarify the terminology: while most applications of FES (Functional Electrical Stimulation) are transcutaneous, 'TENS' specifically refers to a pattern of electrical energy known for its analgesic effect.

In the following sections, we will delve deeper into the TENS method and other less well-known approaches. At Anatomical Concepts, we have worked with a variety of protocols for pain management and these are outlined in this article.

Types of Pain

It might not be obvious that there are, in fact, different types of pain that we might see in a rehabilitation context, and typically, these are classified by their cause or their duration.

Acute pain in our context is closely associated with tissue damage which is likely to resolve relatively quickly. Chronic pain is defined by its persistence for at least 3 months after tissue healing is presumed to have occurred. Some of the terms you might meet in the literature are:

Nociceptive pain arises from tissue damage and activates pain receptors (nociceptors). This can be further divided into:
Somatic pain: Originates from skin, muscles, bones or joints. Often described as sharp, stabbing, or throbbing in character.
1. Visceral pain: Originates from internal organs. Often described as deep, cramping, or burning.
Neuropathic pain is caused by damage to or dysfunction of nerves. Often described as a burning, tingling, electric shock-like, or shooting sensation.

Acute Pain examples might include:

Post-operative pain: Electrical stimulation can help reduce pain and inflammation after surgical procedures and be used to promote healing.
Sports injuries: Sprains, strains, and muscle tears are common sports-related acute pain that may benefit.
Acute back pain: Sudden onset of back pain due to muscle strains or ligament sprains can potentially benefit.

Chronic Pain examples might include

Osteoarthritis: Chronic joint pain caused by the degeneration of joint cartilage and the underlying bone
Rheumatoid arthritis: This chronic autoimmune disorder causes inflammation and joint pain
Fibromyalgia: This chronic pain disorder can cause widespread pain
Neuropathic pain: Pain caused by nerve damage, such as diabetic neuropathy, spinal cord injury, sciatica, or post-herpetic neuralgia
Chronic back pain: Long-lasting back pain resulting from conditions like herniated discs, spinal stenosis or spondylosis.

As we will see, some forms of electrical stimulation are more suited to particular types of pain.

Nerve Fibre Types and Pain

There are three main types of nerve fibres, each playing a distinct role in pain perception:

1. Group A fibres: These are the "speed demons" of the nervous system, transmitting signals rapidly for touch, proprioception (body position awareness), and fast, sharp pain. They're further divided into:

Aα fibres: Thickest and fastest, conveying touch and proprioception.
Aβ fibres: Transmit fine touch and some fast pain.
Aδ fibres: Slightly slower, carrying information about pressure, cold, and intense, pricking pain.

2. Group B fibres: Less common, these medium-sized fibres are involved in temperature regulation and some slower pain sensations.

3. Group C fibres: The slowest and thinnest, these fibres transmit dull, aching pain, as well as itch and burning sensations. They also play a crucial role in chronic pain and neuropathic pain.

It is worth remembering that It is not possible to selectively stimulate only one type of nerve or another, but it is possible to primarily have an effect on a nerve type by setting appropriate parameters on the stimulation device. The large sensory nerves will always be energised first.

What is Electrical Stimulation?

We have lots of articles about electrical stimulation on our site so we only give a brief introduction here.

We have known for many decades that we can use electricity and other forms of energy to produce beneficial effects on muscles, nerves, and tissue. In managing pain, this energy is believed to stimulate nerves, override or block pain signals, and reduce the patient's pain sensation. While the success rate of electrical stimulation for pain can vary depending on the individual patient and their specific condition, many studies have overall shown positive results. Physical therapists and other healthcare professionals may use different types of electrical stimulation depending on their knowledge and experience plus the patient's needs and goals.

When using electrical stimulation for pain relief, electrodes are typically placed on the skin close to or over the affected area and an electrical impulse or stimulation is delivered through the electrodes and into the tissues. The real issue to consider is the exact forms of electrical energy that can provide relief over the spectrum of possible applications.

Forms of Electrical Stimulation

Here is a table summarising different types of electrical stimulation commonly described for acute and chronic pain management, along with typical waveform descriptions.

What Stimulation Protocols are Effective for Pain?

A quick glance at the table above shows that these approaches use widely different stimulation patterns. To discuss the differences in protocols, we must look at the different stimulation parameters; typically the waveform shape, frequency, amplitude, mode of delivery and pulse width. In general terms, and based on experience, the following table summarises in a simplistic way the effect of changing the stimulation parameters.

The TENS Method

Transcutaneous electrical nerve stimulation (TENS) is a method of electrical stimulation primarily aimed at providing symptomatic pain relief. It achieves this by exciting sensory nerves, which are thought to stimulate the pain gate mechanism and/or the opioid system. The different methods of applying TENS relate to these various physiological mechanisms.

Research suggests that TENS provides significantly greater pain relief than a placebo intervention when used effectively. Extensive research has been conducted in both clinical and laboratory settings.

It is important to note that TENS encompasses any electrical stimulation approach using skin surface electrodes to stimulate nerves. However, in a clinical context, it is commonly understood to refer to electrical stimulation specifically intended for symptomatic pain relief. During a literature search on TENS, it is not uncommon to come across other types of stimulation that technically fall under this category.

Typically, TENS has been delivered through small analogue designs and handheld, battery-powered devices. These devices are available for purchase over the counter in many countries for less than £50, although in some locations, they may require a prescription from a therapist, doctor, or other healthcare practitioner. In therapy practice, it is noteworthy that most practitioners consider TENS a viable treatment option for patients experiencing chronic pain too. An evidence base supports its effectiveness in such cases. However, it is important to highlight the increasing body of evidence that supports the use of TENS as a valid and effective intervention in acute pain conditions.

As a treatment technique, TENS is non-invasive and has minimal side effects compared to drug therapy. The most common issue reported is a skin reaction similar to an allergy (affecting approximately 2-3% of patients). This reaction is typically caused by the materials used in the electrodes, conductive gel, or adhesive tape used to secure the electrodes. Skin reactions can also arise if the electrodes are worn out or if the current density is too high.

Nowadays, most TENS applications use reusable, self-adhesive electrodes, which offer easy application, lower incidence of allergies, and overall cost-effectiveness. Some approaches, such as with the Edition 5 we mentioned below, use a wet sponge and carbon-rubber electrode pairing. Garment-based electrodes, such as electrode gloves, are useful for some applications.

The availability of digital TENS machines is increasing, accompanied by the emergence of additional features such as intricate stimulation patterns. However, currently, there is limited clinical evidence to support their enhanced efficacy. It is a challenging area in which to find evidence as there are many possible variables that can be changed as well as difficulty in quantifying pain in the first place.

Stimulation Parameters

The main treatment variables available on modern machines will be outlined before describing how TENS can be employed. The waveform shape used is typically biphasic rectangular. For this application, the waveform shape and fidelity may matter less than when the aim is to produce a muscle contraction. The biphasic nature of the pulse ensures that there is usually no net DC component. This helps minimise any skin reactions caused by the accumulation of electrolytes beneath the electrodes.

Energy and skin effects — The energy is designed to penetrate the skin and deeper tissues to stimulate the sensory nerves

The CURRENT INTENSITY (available strength) will typically be 0 - 80 mA, though some machines may provide outputs up to 100 mA. Although this is a small current, it is sufficient because the primary target for the therapy is the sensory nerves. So long as sufficient current is passed through the tissues to depolarise these nerves, the modality can be effective.

The machine will typically deliver discrete ‘pulses’ of electrical energy, and the rate of delivery of these pulses (the PULSE RATE or FREQUENCY) will usually be variable from about 1 or 2 Hz up to 200 or 250 Hz. To be clinically effective, it is suggested that the TENS machine should cover a range from about 2 Hz to up to 150 Hz.

In addition to adjusting the stimulation rate, it is possible to modify the PULSE WIDTH over a range of approximately 40 to 250 microseconds (μs). (A microsecond is equivalent to one-millionth of a second). However, recent evidence suggests that this control may be less significant than current intensity or frequency, with a clinical setting of around 200μs proving the most effective.

The reason behind such short-duration pulses is their ability to target sensory nerves, which typically have lower thresholds, making them relatively easy to stimulate. They respond to a rapid change in electrical state. There is generally no need to apply a prolonged pulse to force a sensory nerve to depolarise.

In addition, most modern digital machines will offer a BURST MODE in which the pulses will be allowed out in bursts or ‘trains’, usually at 2 - 3 bursts per second. Finally, there may be a modulation approach available, which employs a method of making the pulse output less regular and minimising the accommodation effects often encountered with this type of stimulation. The body naturally adapts to any stimulus presented to it, and although in many situations this is beneficial, for this application, this adaptation or accommodation means that the effectiveness of the stimulation tends to decline over time.

Most dedicated TENS machines offer a dual channel output - i.e. two pairs of electrodes can be used simultaneously. In some circumstances, this can be a distinct advantage, though most patients and therapists will probably use just one channel.

As we mentioned above, not all devices on the market are certified medical devices or offer clarity over the outputs provided.

MECHANISM OF ACTION

PULSE DURATION

As we have seen, a TENS unit delivers a specific type of stimulation that aims to excite the sensory nerves, thereby activating natural pain relief mechanisms. Two primary pain relief mechanisms are considered to be activated: the Pain Gate Mechanism and the Endogenous Opioid System. Let's briefly explore the variation in stimulation parameters used to activate these two systems.

An approach to pain relief involves excitation of the A beta (Aβ) sensory fibres, and by doing so, reduces the transmission of the stimulus from the ‘c’ fibres, through the spinal cord and hence on to the higher centres. The Aβ fibres respond to being stimulated at a frequency of around 80 to 120 Hz. There is NO single frequency that works best for every patient, but this range appears to cover the majority of individuals. Clinically it is important to enable the patient to find their optimal treatment frequency – which will almost certainly vary between individuals.

Setting the machine and telling the patient that this is the ‘right’ setting is almost certainly not likely to lead to the maximally effective treatment, though some pain relief may be achieved.

An alternative approach involves stimulating the A delta (Aδ) fibres, which prefer lower stimulation rates (typically between 2-5 Hz, although some authors consider a more comprehensive range of 2-10 Hz). This stimulation is thought to activate the opioid mechanisms, triggering the release of endogenous enkephalins in the spinal cord. As a result, the activation of noxious sensory pathways is reduced, providing pain relief. Like the pain gate physiology, a single frequency in this range is unlikely to work every time for everyone. Therefore, users should be encouraged to explore various options whenever possible.

One option is to stimulate both types of nerves using burst mode stimulation simultaneously. In this case, the higher frequency stimulation output (usually around 100Hz) is interrupted or burst at about 2-3 bursts per second. When activated, the device will deliver pulses at the 100Hz rate, activating the Aβ fibres and the pain gate mechanism. Additionally, due to the burst rate, each burst will excite the Aδ fibres and stimulate the opioid mechanisms. This approach provides an alternative method to optimise pain relief.

For many patients, this approach provides the most effective pain relief. However, some patients may find it less comfortable than other TENS forms due to a more intense sensation and the potential for muscle 'twitching'.

Traditional TENS

In what we loosely call "traditional" TENS, stimulation is applied at a relatively high frequency (80 - 130Hz) and utilises narrow pulses of short duration. However, it should be noted that the current research literature lacks substantial evidence regarding the effectiveness of manipulating pulse width. Most patients tend to experience the most significant benefit at around 200μs. The stimulation intensity is delivered at a level often described as 'strong but comfortable' in research and treatment guides. While 30 minutes is likely the minimum practical time, it can be applied for longer. The primary pain relief is achieved during the stimulation, with a limited 'carry over' effect, meaning that pain relief diminishes after the machine is turned off. Significant pain relief after stimulation should not be expected.

Acupuncture TENS

So-called acupuncture TENS uses a lower frequency stimulation (2-5Hz) with wider (longer) pulse durations (200-250μs). The intensity employed will usually need to be greater than with traditional TENS - still not at the user's tolerance threshold, but quite a definite, intense sensation. Something like 30 minutes will need to be used as a minimally effective dose.

It takes some time for the opioid levels to build up with this type of TENS, and hence, the onset of pain relief may be slower than with the traditional mode. Once sufficient opioids have been released, however, they will keep on working after cessation of the stimulation. Many patients find that stimulation at this low frequency at intervals throughout the day is an effective strategy. The ‘carry over’ effect may last for several hours, though the duration of this carry-over will vary between patients.

'Brief Intense' TENS

This TENS mode can be employed to achieve rapid pain relief, but some patients may find the strength of the stimulation too intense and will not tolerate it for a sufficient length of time to make the treatment worthwhile. The pulse frequency applied is high (in the 80-130Hz band) and the pulse duration (width) is also high (200μs plus). The current is delivered at, or close to the tolerance level for the user - such that they would not want the machine turned up any higher. In this way, the energy delivery to the patients is relatively high compared to the other approaches. It is suggested that 15 - 30 minutes at this stimulation level is the most that would normally be used.

Burst Mode TENS

As mentioned above, some products may be programmed to deliver 'traditional' TENS, but with a Burst mode activated, causing the stimulation to pause at 2-3 bursts per second. The intensity of the stimulation should be relatively high, although not as intense as with the Brief Intense TENS form. This approach is believed to effectively stimulate both the PAIN GATE and the OPIOID mechanisms simultaneously.

Modulation Mode TENS

In modulation mode, the TENS machine delivers a less regular pattern of stimulation to minimise the accommodation effects of repetitive stimulation. Different machines offer various methods to vary the stimulation pattern, including varying the frequency, intensity, and pulse duration. However, current research does not favour one method over another. This modulation mode can be particularly beneficial for patients who will use TENS for prolonged periods as it slows the accommodation rate and reduces the need for intensity adjustments.

One size fits all?

Frequency Selection: When it comes to selecting frequencies for specific effects, it's unlikely that there's a one-size-fits-all approach. If there were a single frequency that worked for everyone, it would be much simpler, but research (and clinical practice) doesn't support this notion. Patients and their therapists should determine the most effective frequency for their pain by adjusting the stimulation frequency. Users who are advised not to make changes are less likely to experience optimal results.

Stimulation Intensity: As identified above, it is impossible to describe the treatment's most effective current strength. The most effective intensity management appears to be related to what the patient feels during the stimulation, and this may also vary from session to session. Based on recent clinical research, a ‘strong but comfortable’ stimulation level is probably most appropriate for both low and high-frequency TENS applications.

Electrode Placement

Generally, the aim is to target the stimulus at the appropriate spinal cord level (appropriate to the pain) to get the maximal benefit from the modality. Placing the electrodes on either side of the lesion – or pain areas is the most common mechanism to achieve this. Many alternatives have been researched and found to be effective – most of which are based on the appropriate nerve root level :

Stimulation of appropriate nerve root(s)
Stimulate the peripheral nerve (best if proximal to the pain area)
Stimulate motor point (innervated by the same root level)
Stimulate trigger point(s) or acupuncture point(s)

One can employ two channels simultaneously if the pain source is vague, diffuse or particularly extensive. A 2-channel application can also effectively manage a local, plus a referred, pain combination – e.g. sciatica and referred pain in the groin. The low-frequency (Acupuncture-like) form of TENS can be effectively applied to the contralateral side of the body.

I think you will understand by now that TENS is not a one-size-fits-all approach.

Summary so far

TENS, or Transcutaneous Electrical Nerve Stimulation, is a pain management technique that utilises different modes depending on how it has been implemented: Traditional, Acupuncture, Brief Intense, Burst and Modulation. Each mode has specific parameters like frequency, pulse duration and intensity. The effectiveness of therapy varies from patient to patient. Hence, it does not follow a 'one size fits all' approach. The chosen frequency and intensity should result in a 'strong but comfortable' sensation for the patient. Electrode placement plays a crucial role in maximising benefits; it can be achieved through various methods, including positioning around lesion areas or stimulating appropriate nerve roots, motor points or acupuncture points. It's important to remember that the most effective TENS treatment requires tailoring towards individual patient needs.

Professional Applications for Pain in the Edition 5

A product we have experience with is the Stimulette Edition 5 from Schuhfried of Austria. This features seven different approaches to dealing with pain. We often work with clients who have neuropathic pain following a spinal cord injury or trauma and need to offer something to manage pain as well as muscle strengthening. Edition 5 offers a number of approaches to both types of problems and is a good choice for therapists who need a flexible tool to deploy in the field.

We now will give a rundown of the pain-specific waveforms available in Edition 5.

Galvanisation waveforms

The GALV waveform group has three subprograms, GALV10, GALV25 and GALV50, which are all monophasic and used for pain applications or as a “pre-treatment” before using another waveform. This can make muscles more responsive to stimulation (whether innervated or not) when you follow up with another waveform.

These waveforms cannot be used when there are metal implants etc in the area to be stimulated

GALV10 has a maximum current of 10 mA, GALV25 has a maximum of 25 mA and GALV50 has a maximum of 50 mA. These are small currents but the nature of the way they are applied means care must be taken to avoid skin irritation. The maximum intensity is controlled by these currents. The principal application of the GALV waveforms for pain management is via an approach called Iontophoresis which is a physician-only approach.

This was one of the very first such applications of electrical stimulation dating back hundreds of years. It is sometimes referred to as “an injection without a needle” as it actually is a way of delivering a pain relief medicine through the skin via a transfer of ions; literally the medicine is driven through the skin. Iontophoresis is used in Europe and North America as a mainstream application but there are relatively few practitioners in the UK. The process has been used in a broad range of situations including as a remedy for excessive sweating.

In this application, a pair of electrodes are used in the aﬀected area. Liquid medication (perhaps an anti-inflammatory) is placed on a filter paper. which is then placed beneath the sponge of the electrode next to the skin. If the filter paper (with a positively charged medicine) is placed under the anode (positive electrode) the medicine is repelled from the electrode and forced through the skin. If the filter paper (with a negatively charged medicine) is placed under the cathode (negative electrode), the medicine is driven into the skin.

This waveform delivers a direct (galvanic) current which is constant and does not vary whilst active. In eﬀect, the medicine substance to be driven into the tissues needs to be ionic in nature. The eﬀect achieved will depend on the medicine used. (For example, Dexamethasone Sodium Phosphate)

With Edition 5, the wet-sponge pocket/carbon rubber electrode combination is used with the “active” or positive electrode placed on the area to be treated with the medicated paper beneath it. The “inactive” negative electrode is placed adjacent to the positive one.

Even without medication, ion displacement under the positive electrode can provide some pain relief. However, when combined with medication, the effect is significantly enhanced.

It is usually considered that the penetration of the ions into the tissues is likely to be less than 1mm. Any deeper penetration is considered to be due to local capillary circulation eﬀects.

Dosage/Intensity

Edition 5 pain waveforms — The pain related waveforms available in the Edition 5

The maximum permitted current intensity suggested by the manufacturer is 0.1 mA/cm2 of electrode area, irrespective of whether the patient feels anything during the application. Exceeding this intensity risks damage to the skin. In any case, low current intensities are suﬃcient to be eﬀective. Some authors suggest the active electrode should be smaller than the positive electrode but this seems to be based on “rules of thumb” rather than based on research.

Typical treatment durations are 10 to 40 minutes

The actual current intensity used should reflect the suggestions above to avoid skin irritation and will inevitably be affected by the patient’s sensitivity. The frequency of application will vary depending on the application.

Impulse Galvanisation Waveforms

The Impulse Galvanisation waveforms have two subtypes - IG30 and IG50 and both are applicable to acute, chronic, nociceptive and neuropathic pain situations. They tend to be better tolerated than the GALV waveforms. IG30 has a relatively slower analgesic effect but activates the vasomotor nerves, widening the arteries and improving local blood flow. IG50 has a very fast and longer-lasting effect indicated for chronic nociceptive and neuropathic pain.

IG30 pulse shape is triangular (you can choose either monophasic or bipolar) with a frequency of 13 Hz or 8 Hz respectively.

IG50 is effective due to the high frequency of the individual impulses (approx 185 Hz) combined with the low "burst frequency" (approx 8 Hz).

Dosage/Intensity

For joint pain and for radiating pain place one electrode is placed in the spinal cord area where the nerve originates with the second electrode on the distal body part that is painful. The current intensity is increased slowly until the patient feels a “vibration” effect. This current is likely to be quite a low value.

The IG30 waveform can also help with Neuropathic pain.

Although the waveforms are available as monophasic or biphasic forms the biphasic current waveform is primarily used and this is then suitable for situations when there is metal in the treatment area.

Typical treatment times of 10 - 30 minutes as required.

Ultra-Reizcurrent Waveforms

The Ultra-Reizcurrent waveform type is applicable to Acute and Chronic nociceptive and neuropathic pain. This waveform comes via various names including “ultra-stimulation” and “Trabert current”. It could be described as an interrupted direct current and has been popular in Germany and Europe.

Dr Peter Biowski of Dr Schuhfried GmbH favours this waveform in biphasic mode. He recommends setting the intensity to the maximum tolerable level. When the patient’s sensation diminishes the intensity should be increased again. The therapy duration suggested is 30 minutes.

It works according to the gate control theory of pain management and is particularly indicated for acute pain whereby it has a fast action - for example, whiplash injuries.

It is not suitable for persons sensitive to stimulation. Rather like GALV, it is necessary to avoid skin irritation by not exceeding the maximum current intensity of 0.1 mA/cm2
best used in biphasic form although monophasic waveform is also available

The electrodes are applied with one placed where the nerves originate from the spinal cord and the second where the pain arises.

Typical treatment times are 10 to 30 minutes with a frequency of application that could be several times per day in the case of acute whiplash.

Dosage/Intensity

it is suggested that this waveform is used in its biphasic form with the intensity set at the maximum tolerated level. When the sensation experienced by the clients decreases the intensity (current) should be increased again to the maximum tolerated level.

Diadynamic Waveforms

These four waveforms are well-established for pain treatment but should never be used when patients have metal in the treatment area or with those sensitive to stimulation. Like the GALV waveforms, these can be used for Iontophoresis. These waveforms have a history that goes back around 70 years. Engineers would recognise these waveforms as “half or full wave rectified” sinusoidal currents. This class of waveforms is relatively rarely used in the UK, whilst in mainland Europe it has a stronger following. The author has no practical experience with this form.

Most people consider it to be considerably more uncomfortable than other forms of electrical stimulation (like TENS) and this is attributed to the long duration of the 'pulses'.

According to Professor Tim Watson, it was developed in the 1950's, and attributed to Bernard (a French Dentist). The carrier frequency is sinusoidal, operating at 50Hz (or 60Hz USA) which is then rectified (full wave or half wave). The more complex patterns (CP and LP) are derived from some manipulation of these two basic waveforms. We do not believe that this method offers any particular advantage these days.

The terms for the four waveforms relate to the original French terms.

DF = diphase fixe

CP = module en courtes periodes

LP = module en longues periodes

MF = mono phase fixe

As with the GALV waveforms, it is necessary to restrict the maximum current density to a maximum of 0.1 mA/cm2

TENS Waveforms

The Edition 5 unit offers three classes of TENS waveform that follow some of the patterns described earlier. They are referred to by the manufacturer as

TENS - LFT - Typically the starting point for acute and chronic pain
TENS - HFT - Typically suggested for acute pain
TENS - BuT - Typically for chronic pain

The manufacturer contrasts the low-frequency character of TENS-LFT with the high frequency of the other waveforms as they get results by diﬀerent means. The low-frequency character of TENS-LFT generates the secretion of the body’s own pain-reducing hormones. The analgesic effect only increases slowly and a treatment duration of 30 minutes is recommended. Due to the low frequency, the A-delta fibres are stimulated - the opioid mechanism is activated. The TENS-HFT creates a faster pain dulling eﬀect.

TENS-BuT consists of pulses delivered in a “burst”. The suggestion is that burst mode TENS eﬀectively stimulates both the pain gate and the opioid mechanisms simultaneously.

Dose/Application

The suggestion is that for joint pain and radiating pain one electrode is placed in the spinal cord area where the nerve originates and the second electrode is placed in the distal painful area.

For TENS-LFT, you would increase the intensity until a “tapping” sensation is felt. For high-frequency versions, TENS-HFT and TENS-BuT, the sensation will be more like a vibration eﬀect. Treatment duration is 10 to 30 minutes typically.

High Voltage Waveforms

The waveform HV100 is applicable to acute, nociceptive and neuropathic pain - particularly relevant to acute pain. The pain blocking eﬀect is related to the gate control theory and the HV100 is generally suited to those sensitive to stimulation.

The intensity of HV100 is increased until a “vibration” is felt

Medium Frequency Waveforms

Medium frequency currents are sinusoidal currents with a frequency of 1 to 100 kHz. These waveforms are generally perceived as being pleasant and can also be used for patients who are unusually sensitive to electricity. For biphasic medium frequency currents, the DC current component is zero and there is little risk of damage to the skin.

In this frequency range, it is not the individual stimulus but the envelope of the current that has an effect (Gildemeister effect) on acute and chronic nociceptive pain.

The Edition 5 waveform is called a 'MF100' current with an amplitude modulation of 100 Hz. This has a pain-blocking effect according to gate control theory and is, therefore, normally a good starting point for acute pain. The pain-reducing effect of medium frequency current also takes place indirectly by a change of the muscle tone

Conclusion

This document provides a fairly in-depth examination of various waveforms used in pain treatment procedures. In the popular imagination, electrical stimulation for pain relief is all about TENS. However, TENS is not one specific type of stimulation; in fact, there is often confusion in how terminology is applied. Many low-cost so-called TENS devices for pain relief can be found on the market. These may not be regulated medical devices and may offer little clarity in terms of what they actually deliver to the user. Fortunately, electrical stimulation, as offered in these cases, is relatively low risk. They may help or they may not.

In our experience, pain is a complex issue to deal with and it is not possible to have a "one-size-fits-all" type of solution. There are various types of pain and these require a variety of approaches to manage them. The best we can do is to have a sense of direction, but generally, there is much exploration necessary to find relief.

We described some of the manifestations of TENS and how these stimulation forms are believed to induce a beneficial response. Finally, we described a professional stimulation unit, Edition 5, which offers a range of approaches for the management of pain.

Electrical Stimulation in Pain Management?

Types of Pain

Nerve Fibre Types and Pain