Transcutaneous Electrical Nerve Stimulation (TENS) is the most commonly used type ofelectrical stimulation in orthopedic physical therapy. By using 2 or more electrodes placeddirectly on the patient’s skin, an electrical current is run through the body. This is primarily donefor pain management, but does provide some minor additional benefits such as increasedcirculation.
The effects of this treatment are temporary, and is commonly used in physical rehabilitation tohelp patients tolerate the pain and soreness normally present in early stages of treatments.TENS is also frequently used for chronic pain as well, and can help manage symptom flare upswithout additional pharmaceuticals.
There are two prevailing theories for why TENS works: Gate Control, and Endorphin Release.
Throughout our body runs countless numbers of small nerve endings, which carry signals fromvarious receptors in our peripheral nervous system (limbs) to our central nervous system (spinalcord and brain). These smaller nerve fibers feed into larger nerve branches before reaching thespinal cord and then our brain, where the signals are interpreted as different sensations such aspressure, touch, heat, pain, and so on. These common nerve pathways are referred to as the“gates” in gate control theory.
According to this theory, non-painful stimulus can “shut off” painful stimulus from passingthrough these pain gates in the nervous system. The non-painful stimuli will travel to the brainthrough these open gates and be felt while the painful stimulus will not. The pain signals arethus still present, but are temporary either not felt, or are decreased in intensity.
Endorphins are a group of hormones released by your body in response to various stimuli. Theyproduce a variety of effects throughout the body. Certain types of endorphins stimulate youropiate receptors, producing a pain relieving and “feel good” effect. This natural response issimilar to opioid based medication such as morphine.
By using certain parameters of electrical stimulation it is possible to stimulate the release ofthese pain relieving endorphins. Exercise is another effective way to stimulate endorphinproduction. The natural pain relief from exercise can last up to 30 minutes afterwards.
These theories can also be used to explain why rubbing a painful area can alleviate thesensation of pain. Physical therapists will often use manual therapy to massage, mobilize, or
stimulate target areas to decrease perception of pain, and allow patients to perform theirtreatment with less pain or discomfort.
According to both theories, the pain relief is temporary as the sensation of pain is changed butthe affected structures remain damaged or inflamed. As your nervous system returns tobaseline, your brain will once again register the pain signals that were disrupted by electricalstimulation.
As such, TENS is used for pain management only, as the underlying injury is not treated. TENSis most effective in conjunction with a physical rehabilitation program which addresses thedysfunctional structures that are causing pain.
How to Use
Most modern TENS units are user friendly, and straightforward to use. TENS can be appliedvirtually anywhere on the body, and is most effective when placed on areas higher in soft tissue.Many home use units are small enough to be fit in your pocket, or be clipped onto your belt.
Electrode placement is the most important aspect of TENS usage, but does not need to beexact by any means. The electrical current will travel between two electrodes, with the currenttraveling deeper in your body the further apart the electrodes are. Most TENS units now comewith 2 leads with 2 electrodes on each for 4 pads total. Typical placement can be broken downinto creating a box around the affected area, such as placing pads on both sides of the spine forlow back pain.
Once you are satisfied with pad placement, start turning up the electrical intensity to a level thatis strong, but still comfortable and not painful. If you feel muscles contracting or jumping inplace, the intensity is too high. The sensation of TENS is often described as a buzzing ortingling sensation.
Depending on your unit, there will be some number to denote the electrical intensity. Use thisnumber as a general guideline. Do not be concerned if one day the 4 setting feels good, but thenext day the same setting may feel like too much. This is perfectly normal as your body’stolerance will change from day to day.
During treatment, patients will often note the sensation of TENS will decrease, and sometimesdisappear completely. This is normal, and part of your body’s response to the electricalstimulation. You will receive the most benefit from treatment by again adjusting the intensity untilyou feel it strongly. Just be sure to keep it at a comfortable level.
TENS is a valuable tool for pain management, but do remember that it is only temporarilyalleviating the pain. The underlying injury is still present and should be addressed for long termrelief from pain.