Managing Pain and Inflammation with Red Light Therapy

We all know what it’s like to experience pain in some shape or form. Sadly, nearly 70 million Americans suffer from either chronic or high-impact chronic pain (chronic pain that results in a substantial restriction to daily activities)[1] according to a report from 2021. 

Not being able to feel pain at all sounds like a superpower, right? 

But it’s not. 

Pain is our body’s signal to alert us that something is wrong. If your hand is near a sharp knife, you might start to feel pain which alerts you to pull away to avoid further injury. So, believe it or not, pain can be helpful and protect us if we investigate the root cause. 

But what actually is pain?

Both emotional and sensory, pain is a complex and highly personal experience. Skipping the scientific jargon, pain kicks in when our body senses danger to our tissues, triggering our pain-sensing neurons. A whole host of things can stimulate this, such as inflammation, pressure, toxic molecules, and extreme temperatures [2, 3]. 

When our body is under stress or in danger, our immune system protects us by recruiting white blood cells, increasing blood flow, and delivering molecules that help repair injuries and fight infections. This is otherwise known as ‘inflammation’. 

There are 2 types of inflammation:

• Acute (sudden onset) inflammation, which helps our body heal.
• Chronic inflammation, which persists long after the initial insult or danger has passed.

In both cases, soreness and discomfort are common factors, but managing pain becomes significantly more challenging with chronic inflammation. 

So pain is our friend when it helps us out in the short term, but any pain lasting >3 months is considered chronic [4] and can severely impact quality of life. We now know that chronic inflammation underlies many diseases that commonly affect us in the developed world like arthritis, autoimmune diseases, diabetes, heart disease, and even Alzheimer’s. 

Practical approaches to calm inflammation

To effectively ease pain, it's important to focus on reducing inflammation. Everyone is different, though, so make sure to work with your doctor.

Common medications used to treat inflammation

Every week, 23% of people in the U.S. take over-the-counter painkillers such as ibuprofen or Tylenol [5]. Prescription NSAIDs, used for more persistent inflammation, are also common but it's important to note that long-term use of NSAIDs has been linked to kidney disease [6,7].

At-home approaches

Managing stress to reduce inflammation

Stress isn't all bad—mild stress can actually benefit the body. Activities like moderate exercise, cold plunges, and saunas push us out of our comfort zones and trigger adaptation. These activities enhance mental performance [8] and may even play a role in promoting longevity. 
However, repeated or chronic stress can disrupt key bodily systems, such as the immune system, increasing the risk of inflammation and pain[9]. 
Stress can stem from various sources, so there's no one-size-fits-all solution. But you can start by prioritizing high-quality sleep and incorporating daily breathwork—try our 5-minute relaxation session!

Diet: foods to avoid 

• Added sugar (which triggers the release of “inflammatory messengers” [10])
• Saturated fat (trigger inflammation in fat cells [11])
• Refined carbs (have been linked to higher levels of inflammatory markers in the blood) [12]

Diet: food to include

• Omega-3 fatty acids (reduce inflammation and stiffness [13]) - fish, nuts e.g. walnuts, ground flax, flaxseed oil
• Turmeric (contains the chemical compound curcumin that may reduce joint pain and swelling by blocking inflammatory cytokines and enzymes [14]) - add this spice wherever you can! It goes especially well in sauces or juices. Combine with black pepper to help your body absorb the key nutrients, and try to look for one that has been tested for heavy metals. 
• Ginger (reducing inflammation [15] and joint pain [16]) - the dried fresh root of the ginger plant
• Bromelain for its anti-inflammatory properties [17] (pineapple is a great source of this!)
• Fruits, vegetables, and whole grains naturally fight inflammation 
• Vitamin D (plays a crucial role in modulating the immune system [18]) - Egg yolks, salmon, cod liver oil, milk. The best source of all is sunlight! 

Try Red Light Therapy 

Many of us miss out on the sun's healing wavelengths (660 nm and 850 nm), which it emits at a low intensity of 20-40 mW/cm2 [19]. To benefit, we'd need prolonged sun exposure, risking sunburn. Red light therapy (RLT) safely and effectively reintroduces RED and near-infrared (NIR) light into our lives.

Red light therapy is famed for skin benefits [20], yet it was initially discovered when scientists used highly-power red lasers to kill cancer cells. However, they inadvertently used a weaker laser and found that this low dose instead sped up wound healing. 

These benefits can be attributed to the longer wavelengths of red and near-infrared light, which reach deeper into the skin and may be absorbed by mitochondria, supporting the production of ATP [21]. 

How red light might ease symptoms of pain 

Now, pain is incredibly difficult to categorize since it is not a stand-alone ailment, but rather our body’s response to many potential causes.

Dr. Hamblin, a pioneer in red light therapy, has delved into its impact on inflammation [21, 22], a trigger of pain, supported by an increasing number of clinical trials using laser and LED red light. 

A separate paper published in The Journal of Pain [23] highlights how red light through the skin may alter pain perception through a cascade of events and multiple pathways: 

1. Temporarily reducing inflammation 
2. Aiding tissue healing 
3. Modulating pain at the nerve level

For example, near-infrared laser light (810 nm, 50mW/cm2) has been demonstrated effective in altering the pain threshold: one study [24] showed that just 2 minutes of light therapy on the backs of mice could help them handle pain 3 hours later. How? By altering the sensitivity of pain receptors. This graph shows the increase in pain thresholds each day for the mice. Red is the pain threshold before irradiation and blue is the pain threshold 3 hours after red light therapy. Pain threshold averages increased from 20.3 gram-force to 88-gram force post-light treatment!

What about the human studies? 

Knee Pain

In a double-blind randomized placebo-controlled trial [25] assessing the effect of laser and LED on knee pain, 86 patients who were rated highly on the pain visual analog scale (VAS) were recruited to receive 12 treatments, 12 minutes long, with active phototherapy (905 nm super-pulsed laser, 640 and 875 nm LEDs, irradiance ~ 150 mW/cm2, total dose 190.55J) in combination with conventional treatment (like physical therapy and chiropractic care). 

“Phototherapy significantly decreased pain from the 10th treatment to follow-up assessments” which was completed at 1 month.

Osteoarthritis [26]

In this clinical trial on 50 people [27], red, infrared, or a sham light emitters were applied to two points on the knees of patients with osteoarthritis for 15 minutes, two times per day for 10 days.

Compared to baseline scores, those who received the sham light showed no difference in pain scores at the end of treatment. However, in both the red and infrared light groups, there was a 50% reduction in pain scores and improved function after 10 days of treatment.

Fibromyalgia

Fibromyalgia is a chronic condition that causes widespread pain, fatigue, and sleep problems. The exact cause is unknown, but it's associated with musculoskeletal and nerve pain. It can feel like a dull aching or stabbing throughout the body - common symptoms include tender points, headaches, bowel issues, and anxiety. 

In a randomized, blinded, controlled trial [28] studying the effectiveness of light therapy (laser + LED) and exercise training on fibromyalgia treatment in 160 women, they used:

• 1 super-pulsed infrared laser:
• 905 nm
• 2.25 mW/cm2
• 0.3 J

4 infrared LEDs:

• 875 nm
• 19.44 mW/cm2 each
• 5.25 J each

5 minutes of treatment, total dose: 39.3 J.

Light was applied to 10 tender points across the body (e.g. back, sternum, sacrum hip, knee, temporomandibular joint) at which all patients reported pain. Acute pain was assessed, as well as the longer-term effect of the interventions (10 weeks). 

“The phototherapy and exercise treatment improved the pain threshold in women suffering from fibromyalgia. A more substantial effect was noticed for the combined therapy, in which pain relief was accomplished by improving VAS and FIQ scores as well as quality of life.”

It’s interesting to note that the acute pain threshold was improved with phototherapy alone more than exercise alone across all tender points that were irradiated.

10-week (longer term) pain: 

Neck pain

There is “moderate statistical evidence for the efficacy of LLLT in the treatment of acute and chronic neck pain in the short and medium term” [29]. A systematic review and meta-analysis published in the renowned The Lancet included 16 RCTs and assessed the efficacy of PBMT on neck pain. The authors concluded that pain is reduced immediately after treatment for acute neck pain and up to 22 weeks after the end of treatment for chronic neck pain. 

Back pain [30]

A randomized, double-blind, placebo-controlled trial used an infrared LED waistband (800 - 1200 nm wavelength) [31] to assess pain relief in patients with chronic lower back pain.
 
40 patients who had experienced this pain for over 6 years were randomly assigned the IR therapy or placebo, and were treated once weekly for 7 weeks. Pain (on bending forward, bending backward, rotating left and right, bending left and right) was rated on the numerical rating scale (NRS). 

"The mean NRS scores in the treatment group fell from 6.9/10 to 3/10 at the end of the study. The mean NRS in the placebo group fell from 7.4/10 to 6/10”. So while there was also a decrease in pain in the control group, the study demonstrated “significantly greater pain relief in the IR-treated group than in the placebo group” with “reduced chronic back pain by 50% over six weeks”.

Neuropathic Pain 

Neuropathic pain arises from damage or disease affecting the nervous system. It’s often described as shooting pain, a common symptom of MS.

There was a study on the effects of 940 nm LED light on sciatic nerve regeneration in rats [35] after a lesion was made in the nerve. Light, delivered for 7 minutes each day for 10 days, was delivered at 9.5 mW/cm2 held 1cm from the skin. 

“The LED phototherapy with 940 nm wavelength reduced the areas of edema (swelling caused by excess fluid in the tissues), reduced the number of mononuclear cells present in the inflammatory infiltration (i.e. reduced inflammation), and increased functional recovery scores (determined while the animal was still live) at 7, 14 and 21 days.”

Pain from muscle damage

A 2016 pilot study [36] at a university in Pennsylvania assessed the role of 830 nm LED phototherapy in safely accelerating the return to play of injured college athletes.

Light from a head panel (image below) was delivered at 50 mW/cm2, set up 3-15 cm from the target tissue for 20 minutes, starting ASAP after injury. Athletes received 3 consecutive daily sessions, then 3 days without. This cycle continued until marked improvements in VAS scores were observed. Over 15 months, 395 injuries were treated, measuring pain on a visual analog scale (VAS). The time taken for each athlete to return to playing their sport was compared with the anticipated return to play with a conventional intervention.

“830 nm LED-LLLT at 60 J/cm2 safely and effectively decreased both inflammation and pain in injured student-athletes allowing a shorter return to participation in sports activities and training than is generally the case with musculoskeletal or soft tissue injuries. 830 nm LED-LLLT with the system used in the present study was easy to apply, was pain- and side-effect-free, and was well tolerated by all subjects”.

Post-total hip replacement

In a randomized, triple-blind, placebo-controlled clinical trial [37], the goal was to assess the immediate effect of red light therapy (PBMt) on inflammation and pain in patients undergoing a full hip replacement.
18 patients were split into 2 groups to receive either red light therapy or a placebo within 8-12 hours following surgery. The red light device had the following: 

• 4 red LEDs (640 nm, 4.5 J dose for each diode)
• 4 infrared LEDs (875 nm, 5.25 J dose for each diode)
• 1 super-pulsed laser diode (905 nm, 0.81 J dose)

The device applied light to five points over the surgical scar with 2cm between sites. The irradiation time per site was 5 minutes.

To assess changes in the early stages of inflammation, the measured outcomes were pain intensity (using a visual analog scale (VAS) on a scale of 0 - 100) and changes in the levels of inflammatory compounds in blood samples (cytokines IL-6, IL-8, and TNF-α) within 10 minutes of irradiation. 

Immediately following treatment, “PBMt significantly decreased pain compared to placebo-control”. At the post-treatment evaluation, “there was a statistically significant decrease in IL-8 in favor of PBMt group compared to placebo-control group” and a statistically significant decrease in TNF-α in favor of PBMt group”, but the change in IL-6 was not significant.

Temporomandibular (TMJ) diseases

• Randomized, sham-controlled, double-blind clinical trial [38]
• 30 women with myogenous temporomandibular disorder (one of the most common orofacial pains)
• Light therapy group and a control 
• Pain measured on a VAS scale (0-10)
• Received treatment for a total of 6 sessions of 5 minutes
• Device used: 1 super pulsed infrared laser (905 nm, 0.27 J), 4 RED LEDs (640 nm, 15mW), 4 NIR LEDs (875 nm, 17.5 mW)
• Total dose: 39.27

When analyzing pain intensity (VAS scores), “active photobiomodulation was significantly more effective than sham photobiomodulation after 48 h and after six sessions”.

Period Pain

41 women from Korea with menstrual pain were randomly assigned to wear either an LED near-infrared belt that also emitted heat, or to a control group who only used a hot pack on the lower abdomen. [41]

The NIR belt was worn all day from the first day of menstruation until the last.
After measuring menstrual pain intensity (VAS scale), pain duration, and pain medicine use before and after the intervention:

Menstrual Pain: Reduced from 7.68 to 2.55 in the experimental group versus 7.57 to 6.38 in the control group.
Pain Duration: Reduced from 1.82 to 0.96 days in the experimental group with no change in the control group.
Pain Medicine Use: The frequency of taking pain medicine was significantly lower for participants who received the NIR intervention compared to participants who applied the hot pack. I, fact, those who also used red light therapy chose not to use any medication during their menstrual cycle.

 

Conclusion

Despite our best efforts, daily exposure to environmental toxins—from pollution, processed foods, and various body and household products—consistently triggers a low-grade inflammatory response.

Regardless of age, health condition, or lifestyle, everyone can benefit from taking steps to reduce inflammation in the body.

The science behind LED-based technology and its impact on inflammation is promising. Red light therapy is the Swiss Army knife of wellness, not only aiding in inflammation but also supporting skin health [20], muscle recovery [39], joint health [27], and supporting rest [40]. If you're ready to elevate your health, red light therapy could be the tool you need.

Medical Disclaimer: The information contained in this blog post is intended for educational purposes only and should not be used as medical advice. Everyone responds to light differently. Testimonials are not a guarantee of the results you or anyone who uses LUMEBOX will get because your success depends entirely on your circumstances, and the studies on red light therapy shared were not specifically performed using LUMEBOX. Please check with your doctor before using red light therapy and do not change your medical treatments or lifestyle without consulting your physician first. 

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References: 

[1] https://www.cdc.gov/mmwr/volumes/72/wr/mm7215a1.htm
[2] Basbaum AI, Bautista DM, Scherrer G, Julius D (2009) Cellular and molecular mechanisms of pain. Cell 139(2):267–284. https://doi.org/10.1016/j.cell.2009.09.028
[3] Dubin AE, Patapoutian A (2010) Nociceptors: the sensors of the pain pathway. J Clin Invest 120(11):3760–3772. https://doi.org/10.1172/JCI42843
[4] Dydyk, A. M., & Conermann, T. (2023, July 21). Chronic Pain. In StatPearls. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK553030/
[5] Kaufman, D. W., Kelly, J. P., Rosenberg, L., Anderson, T. E., & Mitchell, A. A. (2002). Recent patterns of medication use in the ambulatory adult population of the United States: the Slone survey. JAMA, 287(3), 337–344. https://doi.org/10.1001/jama.287.3.337
[6] Dixit, M., Doan, T., Kirschner, R., & Dixit, N. (2010). Significant Acute Kidney Injury Due to Non-steroidal Anti-inflammatory Drugs: Inpatient Setting. Pharmaceuticals (Basel, Switzerland), 3(4), 1279–1285. https://doi.org/10.3390/ph3041279
[7] Lucas, G. N. C., Leitão, A. C. C., Alencar, R. L., Xavier, R. M. F., Daher, E. F., & Silva Junior, G. B. D. (2019). Pathophysiological aspects of nephropathy caused by non-steroidal anti-inflammatory drugs. Jornal brasileiro de nefrologia, 41(1), 124–130. https://doi.org/10.1590/2175-8239-JBN-2018-0107
[8] Elizabeth D Kirby, Sandra E Muroy, Wayne G Sun, David Covarrubias, Megan J Leong, Laurel A Barchas, Daniela Kaufer (2013) Acute stress enhances adult rat hippocampal neurogenesis and activation of newborn neurons via secreted astrocytic FGF2 eLife 2:e00362
[9] Abdallah, C. G., & Geha, P. (2017). Chronic Pain and Chronic Stress: Two Sides of the Same Coin?. Chronic stress (Thousand Oaks, Calif.), 1, 2470547017704763. https://doi.org/10.1177/2470547017704763
[10] Ma, X., Nan, F., Liang, H., Shu, P., Fan, X., Song, X., Hou, Y., & Zhang, D. (2022). Excessive intake of sugar: An accomplice of inflammation. Frontiers in immunology, 13, 988481. https://doi.org/10.3389/fimmu.2022.988481
[11] Rogero, M. M., & Calder, P. C. (2018). Obesity, Inflammation, Toll-Like Receptor 4 and Fatty Acids. Nutrients, 10(4), 432. https://doi.org/10.3390/nu10040432
[12] Karimi, E., Yarizadeh, H., Setayesh, L., Sajjadi, S. F., Ghodoosi, N., Khorraminezhad, L., & Mirzaei, K. (2021). High carbohydrate intakes may predict more inflammatory status than high fat intakes in pre-menopause women with overweight or obesity: a cross-sectional study. BMC research notes, 14(1), 279. https://doi.org/10.1186/s13104-021-05699-1
[13] Kostoglou-Athanassiou, I., Athanassiou, L., & Athanassiou, P. (2020). The Effect of Omega-3 Fatty Acids on Rheumatoid Arthritis. Mediterranean journal of rheumatology, 31(2), 190–194. https://doi.org/10.31138/mjr.31.2.190
[14] Peng, Y., Ao, M., Dong, B., Jiang, Y., Yu, L., Chen, Z., Hu, C., & Xu, R. (2021). Anti-Inflammatory Effects of Curcumin in the Inflammatory Diseases: Status, Limitations and Countermeasures. Drug design, development and therapy, 15, 4503–4525. https://doi.org/10.2147/DDDT.S327378
[15] Ballester, P., Cerdá, B., Arcusa, R., Marhuenda, J., Yamedjeu, K., & Zafrilla, P. (2022). Effect of Ginger on Inflammatory Diseases. Molecules (Basel, Switzerland), 27(21), 7223. https://doi.org/10.3390/molecules27217223
[16] Altman, R. D., & Marcussen, K. C. (2001). Effects of a ginger extract on knee pain in patients with osteoarthritis. Arthritis and rheumatism, 44(11), 2531–2538. https://doi.org/10.1002/1529-0131(200111)44:11<2531::aid-art433>3.0.co;2-j
[17] Bottega, R., Persico, I., De Seta, F., Romano, F., & Di Lorenzo, G. (2021). Anti-inflammatory properties of a proprietary bromelain extract (Bromeyal™) after in vitro simulated gastrointestinal digestion. International journal of immunopathology and pharmacology, 35, 20587384211034686. https://doi.org/10.1177/20587384211034686
[18] Yin, K., & Agrawal, D. K. (2014). Vitamin D and inflammatory diseases. Journal of inflammation research, 7, 69–87. https://doi.org/10.2147/JIR.S63898
[19] Barolet, D., Christiaens, F., & Hamblin, M. R. (2016). Infrared and skin: Friend or foe. Journal of photochemistry and photobiology. B, Biology, 155, 78–85. https://doi.org/10.1016/j.jphotobiol.2015.12.014
[20] Avci P, Gupta A, Sadasivam M, Vecchio D, Pam Z, Pam N, Hamblin MR. Low-level laser (light) therapy (LLLT) in skin: stimulating, healing, restoring. Semin Cutan Med Surg. 2013 Mar;32(1):41-52. PMID: 24049929; PMCID: PMC4126803.
[21] Hamblin M. R. (2017). Mechanisms and applications of the anti-inflammatory effects of photobiomodulation. AIMS biophysics, 4(3), 337–361. https://doi.org/10.3934/biophy.2017.3.337
[22] de Freitas, L. F., & Hamblin, M. R. (2016). Proposed Mechanisms of Photobiomodulation or Low-Level Light Therapy. IEEE journal of selected topics in quantum electronics : a publication of the IEEE Lasers and Electro-optics Society, 22(3), 7000417. https://doi.org/10.1109/JSTQE.2016.2561201
[23]  Cheng, K., Martin, L. F., Slepian, M. J., Patwardhan, A. M., & Ibrahim, M. M. (2021). Mechanisms and Pathways of Pain Photobiomodulation: A Narrative Review. The journal of pain, 22(7), 763–777. https://doi.org/10.1016/j.jpain.2021.02.005
[24] de Sousa, M. V. P., Kawakubo, M., Ferraresi, C., Kaippert, B., Yoshimura, E. M., & Hamblin, M. R. (2018). Pain management using photobiomodulation: Mechanisms, location, and repeatability quantified by pain threshold and neural biomarkers in mice. Journal of biophotonics, 11(7), e201700370. https://doi.org/10.1002/jbio.201700370
[25] Leal-Junior, E. C., Johnson, D. S., Saltmarche, A., & Demchak, T. (2014). Adjunctive use of combination of super-pulsed laser and light-emitting diodes phototherapy on nonspecific knee pain: double-blinded randomized placebo-controlled trial. Lasers in medical science, 29(6), 1839–1847. https://doi.org/10.1007/s10103-014-1592-6
[26] Vassão, P. G., Parisi, J., Penha, T. F. C., Balão, A. B., Renno, A. C. M., & Avila, M. A. (2021). Association of photobiomodulation therapy (PBMT) and exercises programs in pain and functional capacity of patients with knee osteoarthritis (KOA): a systematic review of randomized trials. Lasers in medical science, 36(7), 1341–1353. https://doi.org/10.1007/s10103-020-03223-8
[27] Stelian, J., Gil, I., Habot, B., Rosenthal, M., Abramovici, I., Kutok, N., & Khahil, A. (1992). Improvement of pain and disability in elderly patients with degenerative osteoarthritis of the knee treated with narrow-band light therapy. Journal of the American Geriatrics Society, 40(1), 23–26. https://doi.org/10.1111/j.1532-5415.1992.tb01824.x
[28] da Silva, M. M., Albertini, R., de Tarso Camillo de Carvalho, P., Leal-Junior, E. C. P., Bussadori, S. K., Vieira, S. S., Bocalini, D. S., de Oliveira, L. V. F., Grandinetti, V., Silva, J. A., Jr, & Serra, A. J. (2018). Randomized, blinded, controlled trial on effectiveness of photobiomodulation therapy and exercise training in the fibromyalgia treatment. Lasers in medical science, 33(2), 343–351. https://doi.org/10.1007/s10103-017-2388-2
[29] Chow, R. T., Johnson, M. I., Lopes-Martins, R. A., & Bjordal, J. M. (2009). Efficacy of low-level laser therapy in the management of neck pain: a systematic review and meta-analysis of randomised placebo or active-treatment controlled trials. Lancet (London, England), 374(9705), 1897–1908. https://doi.org/10.1016/S0140-6736(09)61522-1
[30] Yousefi-Nooraie, R., Schonstein, E., Heidari, K., Rashidian, A., Pennick, V., Akbari-Kamrani, M., ... Mortaz-Hedjri, S. (2008). Low level laser therapy for nonspecific low-back pain. Cochrane Database of Systematic Reviews, (2), Art. No.: CD005107. https://doi.org/10.1002/14651858.CD005107.pub4
[31] Gale, G. D., Rothbart, P. J., & Li, Y. (2006). Infrared therapy for chronic low back pain: a randomized, controlled trial. Pain research & management, 11(3), 193–196. https://doi.org/10.1155/2006/876920
[32] Hsieh, R. L., & Lee, W. C. (2014). Short-term therapeutic effects of 890-nanometer light therapy for chronic low back pain: a double-blind randomized placebo-controlled study. Lasers in medical science, 29(2), 671–679. https://doi.org/10.1007/s10103-013-1378-2
[33] Tantawy, S. A., Abdelbasset, W. K., Kamel, D. M., Alrawaili, S. M., & Alsubaie, S. F. (2019). Laser photobiomodulation is more effective than ultrasound therapy in patients with chronic nonspecific low back pain: a comparative study. Lasers in medical science, 34(4), 793–800. https://doi.org/10.1007/s10103-018-2665-8
[34] DE Oliveira, M. F., Johnson, D. S., Demchak, T., Tomazoni, S. S., & Leal-Junior, E. C. (2022). Low-intensity LASER and LED (photobiomodulation therapy) for pain control of the most common musculoskeletal conditions. European journal of physical and rehabilitation medicine, 58(2), 282–289. https://doi.org/10.23736/S1973-9087.21.07236-1
[35] Serafim, K.G.G., Ramos, S., de Lima, F.M. et al. Effects of 940 nm light-emitting diode (led) on sciatic nerve regeneration in rats. Lasers Med Sci 27, 113–119 (2012). https://doi.org/10.1007/s10103-011-0923-0
[36] Foley J, Vasily DB, Bradle J, Rudio C, Calderhead RG (2016) 830 nm light-emitting diode (led) phototherapy significantly reduced return-to-play in injured university athletes: a pilot study. Laser Ther 25(1):35–42. https://doi.org/10.5978/islsm.16-OR-03xf
[37] Langella, L. G., Casalechi, H. L., Tomazoni, S. S., Johnson, D. S., Albertini, R., Pallotta, R. C., Marcos, R. L., de Carvalho, P. T. C., & Leal-Junior, E. C. P. (2018). Photobiomodulation therapy (PBMT) on acute pain and inflammation in patients who underwent total hip arthroplasty-a randomized, triple-blind, placebo-controlled clinical trial. Lasers in medical science, 33(9), 1933–1940. https://doi.org/10.1007/s10103-018-2558-x
[38] Herpich, C. M., Leal-Junior, E. C. P., Politti, F., de Paula Gomes, C. A. F., Dos Santos Glória, I. P., de Souza Amaral, M. F. R., Herpich, G., de Azevedo, L. M. A., de Oliveira Gonzalez, T., & Biasotto-Gonzalez, D. A. (2020). Intraoral photobiomodulation diminishes pain and improves functioning in women with temporomandibular disorder: a randomized, sham-controlled, double-blind clinical trial : Intraoral photobiomodulation diminishes pain in women with temporomandibular disorder. Lasers in medical science, 35(2), 439–445. https://doi.org/10.1007/s10103-019-02841-1
[39]  Luo WT, Lee CJ, Tam KW, Huang TW. Effects of Low-Level Laser Therapy on Muscular Performance and Soreness Recovery in Athletes: A Meta-analysis of Randomized Controlled Trials. Sports Health. 2022 Sep-Oct;14(5):687-693. doi: 10.1177/19417381211039766. Epub 2021 Aug 25. PMID: 34428975; PMCID: PMC9460079.
[40] Zhao X, Du W, Jiang J, Han Y. Brain Photobiomodulation Improves Sleep Quality in Subjective Cognitive Decline: A Randomized, Sham-Controlled Study. J Alzheimers Dis. 2022;87(4):1581-1589. doi: 10.3233/JAD-215715. PMID: 35491787. 
[41] Lee, J. M., & Kim, K. H. (2017). Effect of near-infrared rays on female menstrual pain in Korea. Nursing & health sciences, 19(3), 366–372. https://doi.org/10.1111/nhs.12356