Electrical stimulation therapies are commonly used modalities within a treatment programs due to their effectiveness in managing pain and aiding in muscle rehabilitation. These modalities are TENS (Transcutaneous Electrical Nerve Stimulation) and NMES (Neuromuscular Electrical Stimulation). While both methods involve electrical currents, they serve different purposes and have distinct applications. In this blog post, we will explore TENS and NMES, how they work, their benefits, and the conditions they are most suitable for.
Transcutaneous Electrical Nerve Stimulation (TENS):
TENS is a non-invasive, minimal side effect therapy that uses electrical current through the
ski n via electrodes, this is felt as a tingling sensation and is used to alleviate pain. The use of TENS in animals is usually well tolerated if introduced correctly. The primary objective of TENS is to stimulate the nerves responsible for transmitting pain signals to the brain. By doing so, it can provide relief from acute or chronic pain conditions.
How Does TENS Work?
The mechanism of action depends on the frequency used, and pulse rate (we can stimulate both mechanisms simultaneously);
Pain Gate Theory: TENS operates on the principle of the pain gate theory when using higher frequency's. Simply put TENS modulates pain signals by stimulating (A beta) sensory nerve fibres, so non-painful stimuli 'block' the pain signals (noxious stimuli) from other fibres (C fibres) providing localised pain relief. There is evidence that suggests TENS has mechanisms of action on both peripheral and central nervous mechanisms to produce analgesic effect.
Endorphin Release: TENS triggers the release of endorphins (the body's natural pain killers) when used at a low frequency. The lower frequency activates the A delta fibres which activate the opioid mechanisms, and provide pain relief by causing the release of an endogenous opiate in the spinal cord, reducing the activation of the noxious sensory pathways.
Enhanced Blood Flow: TENS promotes vasodilation, the expanding of blood vessels, which increases circulation. This increased blood flow delivers nutrients, removes waste, and aids with tissue repair.
Applications of TENS:
Chronic Pain: TENS is a useful none invasive addition to a pain management protocol for chronic pain conditions such as osteoarthritis, and degenerative joint disease.
Acute Pain: TENS is occasionally used to help manage acute pain such as postoperative pain. This is less commonly used in animals.
Muscle Tension: It can also help relieve muscle tension and spasms present.
When not to use TENS:
TENS should not be used with patients that:
Have a pacemaker, metal or electrical implants
Epileptic or undiagnosed seizures
Heart problems
Pregnant patients (without express consent from vet surgeon)
Dermalogica (Skin) issues and wounds
Epiphyseal regions - open growth plates (caution should be applied in young growing patients)
TENS can be used as an at home therapy as part of a holistic approach to pain management. Please ask if you would like more information, or to see if TENS is appropriate for your animal. You can hire a TENS unit from us or alternatively you can purchase a TENS unit from;
Neuromuscular Electrical Stimulation (NMES):
NMES involves delivering controlled electrical impulses that mimic the natural signals (action potential) from the nervous system, to specific muscle groups via electrodes to stimulate muscle contractions artificially. NMES is primarily used to help with muscle re-education, preventing muscle wastage (atrophy) and strengthening. MNES is often tolerated well by animals when they have acclimatised to the feeling.
How Does NMES Work?
NMES delivers a electrical impulse to nerves which mimics an action potential creating a muscle contraction, much like a muscle contracts naturally. The main difference between a natural muscle contraction and a NMES induced muscle contraction is the order in which muscle fibres contract; In a natural contraction usually type 1 (slow twitch) fibres are recruited first, followed by the type 2 fibres larger diameter and produce a lower force fast twitch muscle fibres. This creates a smooth muscle contraction. In electrically induced muscle contractions, type 2 fast twitch, are recruited first, these produce a stronger and faster contraction, creating a jerky movement seen when using NMES. Type 2 fibres often fatigue and atrophy more quickly than type 1 fibres meaning NMES must be used as recommended with suitable breaks in contraction and recovery times. NMES also increase blood flow to an area similarly to TENS this removes waste and provides nutrients aiding healing
Applications of NMES:
Muscle Rehabilitation: NMES activates muscle fibres that may be weakened or compromised due to injury, surgery, or disuse. The controlled contractions mimic natural movements, enhancing muscle strength and functionality. It can also help with maintaining and improving range of motion in joints
Preventing Muscle Atrophy: It can help prevent muscle atrophy when animals may be unable to use certain muscle groups due to injury or immobility. including prolonged periods of rest.
Athletic Training: NMES is used in sporting and working animals to enhance muscle strength and endurance.
Neuromuscular Re-Education: NMES helps re-establish communication between nerves and muscles, retraining the neuromuscular pathways that support coordinated movement.
When not to use NMES:
NMES is contraindicated in animals that:
Have a pacemaker, metal or electrical implants
Epileptic or undiagnosed seizures
Heart problems
Pregnant patients (without express consent from vet surgeon)
Dermalogica (Skin) issues and wounds
Epiphyseal regions - open growth plates (caution should be applied in young growing patients)
NMES can be a really helpful tool in aiding rehabilitation. If you want to know if NMES is something that may help your animal let us know and we can talk you through the uses. You can contact us to hire a NMES machine for the duration of your animals rehabilitation.
Key differences between NMES and TENS
TENS | NMES |
TENS primarily targets pain relief by interfering with pain signals | NMES is focused on muscle rehabilitation and strengthening through muscle contractions |
TENS electrodes are placed proximal and distal to or directly over the painful area. | NMES electrodes are positioned with the negative black pin near the upper insertion of the muscle and the positive red pin over the motor point (usually in the muscle belly) of the targeted muscle. |
Small, affordable, and battery operated. Good for at home use as part of a pain management program | Small, often battery powered and slightly more expensive than a TENS unit but still reasonably affordable for regular use. Good for at home strength and condition and atrophy prevention |
TENS and NMES are both valuable electrical stimulation therapies with distinct purposes. TENS is ideal for managing pain and providing relief in various chronic and acute pain conditions. In contrast, NMES excels in muscle rehabilitation, aiding in muscle re-education, and preventing muscle atrophy. Both should be used as advised by your Vet physio, or Vet. When used to the sensation of the devices, which usually only takes a moment or two when used correctly most animals tolerate and enjoy there sessions with NMES and TENS.