When it comes to performance recovery, we use ice, heat, massage, and so on. It’s typical for us to find ways to mask the pain, think NSAIDS and topical analgesics- think icy hot. This is where TENS comes into play, in fact electrical stimulus to treat pain has been utilized for centuries, from the Roman Emperor Claudius standing on electric fish to the stone carvings of fish organs used to produced an electrical charge to treat pain.
What is TENS?
“TENS” stand for Transcutaneous electrical nerve stimulation (TENS). It’s a non-pharmacological device, typically hand held, used for treatment of acute and chronic pain conditions.
The TENS device delivers alternating currents to electrodes placed around the painful area. The small battery powered device activates a complex neuronal network to reduce pain by activating descending inhibitory systems in the central nervous system to reduce hyperalgesia.
Say what?! Basically it’s supposed to help reduce the body’s pain signals, therefore diminishing the feeling of “pain”, kind of like “Tiger Balm” or “Icy-Hot”.
How Does TENS Works
If you want a more in-depth answer here’s Carol et al’s explanation on the mechanism of TENS reduction on analgesia:
“TENS activates a complex neuronal network to result in a reduction in pain. At frequencies and intensities used clinically, TENS activates large diameter afferent fibers. This afferent input is sent to the central nervous system to activate descending inhibitory systems to reduce hyperalgesia. Specifically, blockade of neuronal activity in the periaqueductal gray (PAG), rostral ventromedial medulla (RVM) and spinal cord inhibit the analgesic effects of TENS showing that TENS analgesia is maintained through these pathways. In parallel, studies in people with fibromyalgia show that TENS can restore central pain modulation, a measure of central inhibition. Therefore, TENS reduces hyperalgesia through both peripheral and central mechanisms.” (1)
Simply put, TENS has an analgesic effect but if used correctly it can have a longer lasting opioids effect, according to Woolf et al (7).
Dosing of TENS
In a majority of the research, the intensity of the TENS has shown to play an important role in the positive effects. According to Sluka et al “, stimulation amplitude must be of sufficient strength to produce an analgesic response. Three recent studies in individuals who were healthy support this finding. Specifically, TENS delivered at a strong but comfortable intensity provided a significant analgesic effect, whereas TENS delivered at or below sensory threshold was ineffective. Thus, amplitude must be increased to an adequate level to produce analgesia.” (2)
In other words, the intensity should be high enough to cause a little stimulation, but not too high that it’s uncomfortable and not so low that you can barely feel it. Hit that sweet spot.
TENS Usage Frequency
TENS just like anything has to be utilized on a consistent basis for it to yield positive effects. It’s just like exercise, if you workout once every other week, your progress will be minimal vs. x3 a week on a consistent basis.
The sweet spot seems to be at the x2 a week according to Marchand et al. (3)
TENS Long Term Usage
Chabal et al (4) research on long-term use of TENS found it significantly reduced the use of pain medicine and PT/OT over a span of 40+months. However this study is very flawed, where a majority of the subjects were interviewed by phone via an independent research firm.
There just isn’t enough long term controlled studies to show the positive or negative effects on long term usage, so use it carefully. My suggestion would be to first try it x2 a week for x2-3 weeks and then see then start to make adjustments based on those baselines.
Does TENS Work?
The always hated “yes and no” or depends is the answer here. As of now there’s a lot of conflicting research that includes various population-specific reviews and amount of subjects.
With that said, there is positive research that shows if used near the painful area and applied at a strong, non painful intensity it can have a analgesia effect, think “icy hot” (1). However, most of these reviews are hampered by the design, inconsistency of the TENS power output, and the study being a small short trial.
This doesn’t mean that the research isn’t accurate, it’s just inconclusive.
To take it one step further, a study on the effectiveness of TENS on osteoarthritis, a disease that affects synovial joints causing degeneration of the cartilage, in the knee showed that TENS unit combined with a acupuncture needle (5) to be bit more effective. Basically, they stick a need in the muscle, charge it up, and then zap!
Cheap or High End TENS Unit
If you do decide to move forward with a TENS unit, I’d suggest the $30-50 range units, at least to start. As of now, I haven’t seen a drastic difference to justify spending upwards of $700.
The research shows that as long as you’re getting enough intensity in the stimulus and frequency the TENS should show some type of positive effect. And that’s exactly what the $30-50 range does, most are pretty ugly, cheap looking, and are packaged very nicely but they do the job.
HealthmateForever TENS (FDA approved)
Price: $50
I have this cheap looking iPod looking TENS but don’t be fooled it works amazingly well and packs a punch! 
truMedic TENS (FDA approved)
Price: $34
I will say that both are a bit annoying to program but it’s still pretty simple to do and just as effective.
Conclusion
I find TENS to help relax the muscle for a short period. How it’s done is still up in the air- hormone release, interference with nerve signals, etc…In the end, TENS can be a useful TOOL in your recovery, especially for athletic purposes – recovery for your next workout, pulled muscles, an analgesic effect etc… but it’s only a piece of the whole- ice, massage, stretching, etc…
To clarify, this isn’t beauty method to help you “sculp, lean, tone” your muscles. Anyone that promotes this use is just trying to take advantage of those looking for a quick fix:
Research Citation:
1: Vance, C. (2014). Using TENS for pain control: The state of the evidence.Pain Management, 197-209.
2: Sluka, K. (2013). What Makes Transcutaneous Electrical Nerve Stimulation Work? Making Sense of the Mixed Results in the Clinical Literature. Journal of the American Physical Therapy Association, 1397-1402.
3: Marchand S, Charest J, Li J, et al. Is TENS purely a placebo effect? A controlled study on chronic low back pain. Pain. 1993;54:99–10.
4: Chabal, C. (1998). Long-term transcutaneous electrical nerve stimulation (TENS) use: impact on medication utilization and physical therapy costs. Clinical Journal of Pain. 66-73.
5: Osiri, M. Transcutaneous. (2000). Electical Nerve Stimulation for Knee Osteoarthritis. Cochrane Database System Review. 4.
6: Walsh D (1997) TENS: Clinical Applications and Related Theory. London: Churchill Livingstone.
7: Woolf C (1991) Segmental afferent fibre-induced analgesia: transcutaneous electrical nerve stimulation (TENS) and vibration. In: Wall P, Melzack R (eds) Textbook of Pain. London: Churchill Livingstone.