Whether you are looking for a therapist to recover from an injury or looking for a tool to boost your fitness and strength, electrical stimulation might be in your future. There are many types of electrical muscle stimulators, (EMS) and they work in different ways and come in many different shapes and sizes. The primary ones we will talk about in this article are TENS units (Transcutaneous Electrical Nerve Stimulation), and NMES units (Neuromuscular Electrical Stimulation). These units work in the same way but target different nerves and areas of the body, so it’s important to know what is best for you, and what would benefit you the most. It’s important to note that TENS units target the sensory nerves of the body, and NMES units target the motor nerves of the body. Many people have experienced these types of devices, more than likely at a physical therapist’s office, however, the information given to them was limited. In this article, we will go over the two types of nerves these units affect, and the primary differences between NMES and TENS units.
The sensory nerves are part of the PNS (Peripheral Nervous System) and contribute to the processing of input from the environment. This could be a simple touch, to being pushed. This system allows the body to gather information and sends it to the brain for processing. Once the brain processes the information given to it, a signal is sent to that area of the body to act. For example, if you touch a hot stove, sensory nerves send the signal to the brain, the brain thinks “I should move my hand” and you move your hand. This information is sent and processed at an extremely fast rate. This is known as motor function, which is the response to the information.
Motor nerves are directly involved in neuromuscular activity and control. Motor behavior is primarily learned and enhanced through stimulation of these nerves so it’s important to understand how they react, and what they are involved in. Motor nerves are involved in appropriating signals from the CNS to the peripheral nerves. Motor nerves are directly involved in muscle control, because these nerves tend to be directly attached to the muscles. “Motor nerve axon terminals innervate skeletal and smooth muscle, as they are heavily involved in muscle control.”(1) Motor nerves are directly involved in enhanced
muscle stimulation, enhancing muscle torque and power, and creating a stimulating environment for muscles to thrive in. (2)
NMES VS TENS
So what is the main difference between these two types of stimulation? The two main differences are the stimulation type, and the area it affects. NMES stimulation targets the MOTOR nerves. Directly affecting the muscle and stimulating the area. This creates more muscle contraction, which means more muscle fiber involvement and stimulation. While TENS units target the sensory nerves, where the brain interprets the signal, primarily causing the muscle to contract, without the use of all the muscle fibers. These two might be similar, however depending on what your goals are, and what part of the rehabilitative process you are in, one might be better than the other.
“The use of NMES to gain muscle strength or performance in high-level athletes has been employed with frequencies by physiotherapists who work in sports. It was found that the medium frequency current is more comfortable and is able to generate a peak torque significantly higher than the low-frequency current.” (3)
This means NMES technology can not only assist in the rehabilitative process for serious injuries but also assist in top athletic performance. Assisting in a natural boost in performance due to the enhanced muscle stimulation and the enriched environment caused by this stimulating effect.
There seem to be many different types of uses for Electrical stimulation, and the studies continue to pour in. Electrical stimulation studies have only just begun to gain true traction and value, and we are already beginning to see a vast array of uses and results stemming from these. There are many different types of tools, and different types of stimulators, so it’s important to understand the difference between them and understand how you react to these types of stimulations and tools. Ask your physical therapist for the advice!
Koop, Lindsey K. “Neuroanatomy, Sensory Nerves.” StatPearls [Internet]., U.S. National Library of Medicine, 7 Apr. 2019, www.ncbi.nlm.nih.gov/books/NBK539846/.
“Motor Nerve.” Wikipedia, Wikimedia Foundation, 5 Feb. 2020, en.wikipedia.org/wiki/Motor_nerve.
Pinfildi, Carlos Eduardo, et al. “NEUROMUSCULAR ELECTRICAL STIMULATION OF MEDIUM AND LOW FREQUENCY ON THE QUADRICEPS FEMORIS.” Acta Ortopedica Brasileira, ATHA EDITORA, 2018, www.ncbi.nlm.nih.gov/pmc/articles/PMC6220661/.