Pain is something that we all experience and is the most common symptom that causes individuals to seek medical attention. For some individuals, pain is rare and short-lived, for others, the sensation of pain has become embedded into their daily lives. I can’t tell you how many patients tell me “I always have pain, it is something I have learned to live with.” As a Physical Therapist, educating my patients on their injuries, diseases, and pain is the most important aspect of my job.
Pain is a sensation which everyone experiences and reacts to differently, making explaining and understanding pain very complex. Pain varies in intensity and duration with some pain very strong only lasting seconds or chronic pain lasting years. Although the ability to feel the sensation of pain is necessary and essential to help protect our bodies from further damage or permanent injury (for example, pulling our hand away from a hot stove), long-term, chronic pain can be extremely limiting. Chronic pain affects our ability to perform our daily tasks, move, work, and greatly impact our quality of life.
The Sensation of Pain
We have receptors in our bodies called nociceptors that sense potentially threatening sensations. These nociceptors respond to damaging or potentially damaging stimuli by sending signals to the spinal cord and then up to the brain. Once the brain receives this signal, it determines whether or not the signal is an actual threat. If deemed a threat, your body creates the sensation of pain to direct your attention to that area of the body.
We have two types of nerve fibers which carry the pain sensation, thus leading to varied pain sensations. A-delta fibers are responsible for the initial quick intense sharp pain (ie. sharp pain felt with stubbing your toe), while C-fibers are responsible for the longer lasting dull pain felt afterward (longer chronic pain). In addition to the pain receiving fibers (A-delta and C), we also have non-nociceptive fibers, A Beta fibers, which allow us to feel non-painful stimuli, such as touch, pressure, and vibration. The cool thing about A Beta (non-painful) fibers is that they can block the A-delta and C fibers, essentially minimizing the sensation of pain. This is why rubbing our toe after we stub it on the corner of a table can help our pain subside.
The Gate Control Theory of Pain
The Gate Control Theory of Pain works by using the sensation of non-painful input to interfere with the painful noxious stimuli. Your brain and spinal cord can only transmit and handle a certain number of stimuli. By over stimulating the A Beta fibers (non-painful), we can jam the system and the sensation of pain has a harder time making it through, essentially closing the “gate” to the brain.
We can utilize this blocking system as physical therapists to help reduce pain in patients. These options include a TENS unit and the use of over-the-counter topical analgesics (Biofreeze, IcyHot, Bengay). Many people have heard of or have seen commercials for these products, but do not know how or why they work.
TENS stands for transcutaneous electrical nerve stimulation and can be used and has been found effective for individuals with osteoarthritis, muscle inflammation, muscle spasms, and acute and chronic pain (1). The device generally comes with two to four pads that are placed around the area of pain and will provide a vibration or tingling sensation. The tingling sensation provided activates the large A-beta peripheral fibers and modulates/blocks the pain signals being sent to the brain. The TENS unit can generally offer relief within five to ten minutes of using the device. The duration of how long the device should be used at any given time varies, but can be generally worn for up to an hour. Some individuals choose to wear their device longer to help them get through their daily and work-related activities with improved ease. Conventional TENS can be used one or two times daily or as often as needed.
Another way to utilize the Gate Control Theory of Pain is to use over-the-counter analgesic creams such as Biofreeze, IcyHot, or Bengay. These creams are applied topically (on the skin over the painful area) and can be used for most musculoskeletal injuries involving muscle or joint pain (2). These products use Menthol to help alleviate muscle or joint pain by using the cooling sensation to distract your brain from the pain. Once the cooling sensation of menthol is felt, it activates cold receptors in the skin, again stimulating our A Beta fibers. You can use these topical analgesics by applying them up to three to four times a daily.
As I inform all of my patients, every individual is different. What may work for one patient may not always work for another. TENS and topical analgesics can provide temporary relief, they are only a piece of the puzzle when it comes to abolishing pain. These products should be used in conjunction with other conservative treatments to heal the cause of the pain. Always consult with your Physician or Physical Therapist as to what treatment option may be best for you.
1. Butler, David S. The Sensitive Nervous System. Noigroup Publications, 2000.
2. Hayes, Karen W., and Kathy D. Hall. Manual for Physical Agents. Pearson Education, 2012.
Page, Phil, and Lacy Alexander. “The Clinical Effectiveness of Biofreeze Topical Analgesic on Musculoskeletal Pain: A Systematic Review.” JPHR: Journal of Performance Health Research, vol. 1, no. 1, 2017.