Neuromuscular and Muscular Electrical Stimulation (NMES)
Definition[edit | edit source]
Neuromuscular and Muscular Electrical Stimulation (NMES) is a modality that sends electrical impulses to nerves which causes the muscles to contract mimicking the action potential coming from the central nervous system. It may be applied during functional movement or without functional movement. It has been used throughout the years for strengthening and maintaining muscle strength and preventing atrophy, especially with immobilized patients.
Indications[edit | edit source]
- To improve muscle strength and prevent muscle atrophy
- To improve and maintain the range of motion around a joint
- To reduce muscle spasticity and spasms
- To increase cardiovascular function through the activity of large muscle groups
Contraindications[edit | edit source]
- when placed over the carotid sinus
- when the patient has a pacemaker
- when we have areas of active tissue infection and devitalized skin
- when the patient is unable to comprehend instructions and provide feedback
- when the patient is pregnant
- when the patient has a peripheral vascular disease
Electrically Stimulated Muscle Contraction vs Physiological Muscle Contraction[edit | edit source]
The two main differences between electrically stimulated muscle contractions and physiological muscle contractions are the order of motor unit recruitment and the smoothness of the onset of contraction. During normal physiological muscle contractions, the first fibers to be recruited are the slow-twitch type 1 muscle fibers, and then later the large diameter muscle fibers, which produce low-force contractions and are fatigue and atrophy resistant and the contraction is smooth. On the contrary, during electrically stimulated muscle contractions, the first muscle fibers to be recruited are the large-diameter fast-twitch type 2 muscle fibers which produce the strongest and quickest contractions, fatigue, and atrophy rapidly and produce jerky movements which is why upon electrical stimulation by NMES long rest times should be provided between stimulated contractions.
Application of NMES[edit | edit source]
First, the patient should be seated comfortably in a way that allows muscle relaxation which is necessary for easier muscle stimulation. Then, the skin should be inspected to make sure there are no skin abrasions and injuries. Following that the skin should be properly cleaned with a piece of cloth and water or alcohol-based wipes and it's very important to make sure the skin has been properly dried before the application of the electrodes on the skin.
There is a wide variety of electrodes that can be used including self-adhesive electrodes which are quick and easy to use due to them already having a layer of conductive material on their surface, unlike carbon-rubber electrodes which are normally coupled to the skin by electrical conductive gel. These electrodes should be placed away from the joints and properly attached to the skin to avoid pain and discomfort. These electrodes can be placed either in a way where the cathode is placed on the motor point of the target muscle and the anode proximally on a nearby muscle supplied by the same nerve and this placement is called monopolar electrode placement and used when targeting small muscles. The bipolar electrode placement involves placing both electrodes on the muscle belly or one at the proximal end and another on the distal end of the muscle. The size of the electrode depends on the size of the muscle or muscle group to be stimulated where stimulating muscles for example the quadriceps or the hamstring muscles require large electrodes.
During electrical stimulation, it's important to increase the intensity of the stimulation gradually and to the maximum tolerable extent by the patient. For innervated muscles normally, the shorter the pulse duration, the greater the pulse amplitude should be whereas for denervated muscles, both pulse duration and pulse amplitude should be greater than that of innervated muscles which is particularly important to ensure stimulation and sudden contraction of the muscle.
Parameters[edit | edit source]
- Frequency (Hz) is the number of pulses in one second (20-50 pulses per second)
- Pulse Duration (microsecond) for small muscles is approximately 150-200 and for large muscles 200-300
- Ramp time is at least 2 seconds
- ON: OFF time ratio should be set in a way where off time is three times the on time
- Treatment time should be between 20 and 30 minutes
- The frequency of the sessions should be three times a week
References[edit | edit source]
- Hainaut KH. Duchateau JD. Neuromuscular Electrical Stimulation and Voluntary Exercise.Sports Med. 1992;14(2):100-13.
- The Association of Paediatric Charted Physiotherapists. Publications. Available from: https://apcp.csp.org.uk/content/guide-use-electrical-stimulation-paediatric-neurodisabilityn (accessed 18/12/2022)
- Lago AL. Oliveira AO et al. The Effects of Physical Therapy with Neuromuscular Electrical Stimulation in patients with Septic Shock: Study Protocol for a Randomized Cross-Over Design. Medicine. 2018; 97(6).
- Barss TB., et al. Utilizing physiological principles of motor unit recruitment to reduce fatigability of electrically-evoked contractions: a narrative review. Archives of physical medicine and rehabilitation. 2018;99(4):779-791.
- Nussbaum EN., et al. Neuromuscular electrical stimulation for treatment of muscle impairment: critical review and recommendations for clinical practice. Physiotherapy Canada. 2017; 69(5): 1-76.
- Gorgey AG. Dudley GD. The role of pulse duration and stimulation duration in maximizing the normalized torque during neuromuscular electrical stimulation. Journal of Orthopaedic & Sports Physical Therapy. 2008;38(8): 508-516.
- PhysioU. How to prepare for Neuromuscular Electrical Stimulation (NMES)?. Available from: https://www.youtube.com/watch?v=_eBUskzKaPI [last accessed 12/18/2022]
- Baldwin EB., et al. Wide-pulse-width, high-frequency neuromuscular stimulation: implications for functional electrical stimulation. Journal of Applied Physiology. 2006; 101(1):228-240.