Red Light Therapy Pulsing: Worthless Or Useful? A Science Breakdown

Bart hree from team Alexfergus. In this blog post, I'll talk about red light therapy pulsing. I'll break down the science on this topic. The topic is somewhat controversial as not everyone agrees that pulsing is beneficial.

But first a definition:

Pulsing is defined as momentary peaks of light that are emitted from a red light therapy device. So, at different intervals of time, there's either light emitted from the device or not. Continuous exposure is the opposite of pulsing as there's light emitted at all moments of time.

Pulsing is controversial within the red light therapy space though. To demonstrate that point, I'll quote some red light therapy blogs on this topic. First, the Red Light Therapy At Home website states:

"pulsing in red light therapy does not add to its therapeutic benefits" (1).

And, as PlatinumLED states:

"While using pulsed led light has become something of a trend, don’t fall for this flashy new application method. It was created for the world of laser therapy, and that’s where it should stay. If you’re using an LED panel, continuous, steady usage will yield the best results." (2)

Many agree with this assessment. GembaRed, for instance, states that:

"So if a company is advertising pulsed red light therapy for some special medical application or benefit, then be wary!

If the pulsing is a designed to mitigate heating or transcranial application for entrainment then that would be practical and acceptable.

But if companies like Joovv are just adding pulsing to their long list of gimmicks and making extra medical claims, then make sure to dig into the science yourself." 
(3).

(Removed bold emphasis in the text above)

So is pulsing worthless or is there something to it? In this blog post, I'll explore that question. I'll look at 15 randomly picked different studies, summarize them, and then give you my viewpoint on the topic. Below I've also summarized the findings:

 

Red Light Therapy Pulsing Science Review Summary:

  • A pulsing benefit is that it allows you to use higher power densities, which give higher penetration depths because tissues are less prone to overheat during this process. Reading the studies, 
  •  Pulsing may affect human biology through other mechanisms, such as affecting the movement of ions (potentially charged atoms) across the body. More research is needed on these mechanisms.
  • Overall, many studies show a difference in outcome when pulsing is used compared to continuous waves. The problem, however, is the unpredictability. Scientists don't know what laws underlie the mechanisms by which pulsing affects human physiology. Different pulsing parameters have different effects and the underlying mechanisms seem complex right now.
  • (Almost) all of the pulsing studies use lasers, not LEDs. And, even though it's known that LEDs work very well for red light therapy, some research is necessary to establish that pulsing also has an effect with LEDs instead of just with lasers.
  • If you use pulsing, make sure to use protective eyewear. Pulsing can create fatigue, brain fog, and even epileptic attacks in some people so it's not without risk. Only use pulsing frequencies on your body, and never emit the pulsed light into your eyes. 
  • Due to the absence of high-quality evidence, most people should just stick to the basics of red light therapy and don't bother too much about pulsing. The effect-size - so how big the impact is of pulsing versus continuous - doesn't seem huge. You will get results with continuous as well as pulsing and the danger is that people start to overthink the effect pulsing has, thereby overcomplicating their red light therapy sessions.
  • My methodological quality isn't perfect. With a full review, I might gotten slightly different outcomes as I've selected 15 studies randomly instead of taking all the available evidence into account.

 

Red Light Therapy Pulsing Basics: What Are The Effects?

In this section, I'll look at the basics of red light therapy pulsing. In the next section, I'll consider 15 different pulsing studies. As stated before, I've randomly selected these studies. The studies exclusively come from the PubMed website. I tried to include studies that compare continuous exposure to pulsing as much as possible.

First, I consider a systematic review of 2010 aimed at determining whether there's an effect of pulsing or not and its basics (4). Although I'm oversimplifying a bit, systematic reviews summarize existing studies on a given topic and aim to draw an overarching conclusion from all the earlier results. This 2010 study included all pulsing studies from the 1970 - 2010 period. The abstract of the study concludes the following:

"There is some evidence that pulsed light does have effects that are different from those of continuous wave light."

So, right away, I get the impression that there is something to pulsing. At the very least, pulsing changes the treatment parameters of the biological effects of red light therapy. But, of course, different effects don't necessarily mean that the effects are positive. 

The study also gives a nice explanation of what happens in pulsing in terms of power output:

  • There's an on time and an off time. During the off time, there's no power output (obviously). The power output or "irradiance" is the amount of light - or the quantity of photons - emitted from a red light therapy panel or laser at any given time. 
  • Although a bit more of an advanced concept, the on and off times don't need to be equally long. The off period can be longer than the on period, or vice versa. So a red light therapy device or laser can emit light for 20 milliseconds, and then shut off for 80 milliseconds. 
  • The frequency is related to that on and off time. A higher quantity of on-and-off alterations at any given time results in a higher frequency. To make that concept easier to understand, simply imagine activating a light bulb many times a second. That frequency is measured in Hz. So 40 Hz pulsing means that the red light therapy panel is activated and deactivated 40 times a second. Of course, a very high pulsing level is indivisible to the human eye. For that reason, a monitor that has a "frame rate" (pulsing frequency) of 20 Hz is very stressful to the human brain but at 60 Hz the light looks very continuous.

Next up, the systematic review also provides a reason why you would want to use pulsing:

"In instances where it is desirable to deliver light to deeper tissues increased powers are needed to provide adequate energy at the target tissue. This increased power can cause tissue heating at the surface layers and in this instance pulsed light could be very useful. Whereas [continous waves] causes an increase in temperature of the intervening and target tissues or organ, pulsed light has been shown to cause no measurable change in the temperature of the irradiated area for the same delivered energy density."

In plain English, this statement means that you've got a period where your tissues are exposed (the on period) and a period where your tissues are not exposed to the light (the off period). As red light therapy is slightly heating your tissues, the off period allows your tissues to continuously cool down.

I'll go into the benefits of that could down period in a second.

First, you probably know that Alex tests the power output or irradiance of all panels during his red light therapy reviews. Alex uses a spectrometer for that goal. As a result, Alex measures the power output for each panel, such as the peak power output, or an average power output over different areas of a red light therapy panel. 

That power output or irradiance is expressed as mW/cmor milli-Watts per centimeter-squared. A higher power output means that more light is delivered to the tissues, and a lower power output entails the opposite. However, red light therapy is heating at higher power outputs. And, by using pulsing, you can reduce the amount of heating that occurs in tissues.

The researchers of the systematic review state that:

"For example, when [continous waves] power densities at the skin of ≥2 W/cm2 are used, doubling the [continous waves] power density would only marginally increase the treatment depth while potentially significantly increasing the risk of thermal damage; in contrast, peak powers of ≥5 W/cm2 pulsed using appropriate ON and OFF times might produce little, or no tissue heating." (4).

So, pulsing can help you achieve a higher power output at a specific time interval if tissue heating is an issue. It's already known that higher dosages (irradiance) cause deeper penetration of tissues (5; 6). In this regard, pulsing can thus be a benefit.

Let's explore what these benefits mean for you: you could use a pulsed red light therapy panel, such as the LightpathLED Large Multiwave Pulsed or the Mito Red MitoADAPT, stand closer to the panel and use pulsing for deeper penetration depth while not heating up your tissues.

 This pulsing effect can be a great benefit for harder-to-treat tissues like the brain. Due to the bones around your head, the light has a much harder time penetrating deeply. For that reason some of the products on the market like the Vielight. Red light therapy through the nose offers similar benefits. 

Next up, there's another reason why pulsing might be beneficial. The researchers of the systematic review write about the fact that the pulsing frequencies may align with frequencies used in human biology itself - although this mechanism is somewhat speculative (4).

Here's how:

First of all, pulses exist within the human brain in certain frequencies. These can be delta waves that are active in deep sleep, for instance, or beta waves that are active during wakefulness. Alpha is also very well-known because it's a dream-like state associated with creativity. Alpha brainwaves occur between 7 and 13 Hertz (Hz), Beta between 14 and 40, and delta between 1-3 Hz. Normally, these brainwaves are measured with Electroencephalography (EEG) in neurological studies.

By matching the Hz frequencies of red light therapy with the brain waves, theoretically, there could be a biological effect. More research is needed though, with regards to red light therapy in this area. 

Nevertheless, studies using auditory stimuli find that when these brainwaves are activated many different effects are found (7; 8; 9). Cognition is improved, for instance, while anxiety and stress are reduced. Pain perception is also reduced, with migraines and PMS. Benefits might also exist for neurodegenerative diseases.

Again, some of the results of pulsed red light therapy studies might rely on this specific mechanism.

Other mechanisms are explained in the systematic review as well to explain why pulsing may have a biological effect (4). First, the movement of charged particles called "ion" may be altered by pulsing. Ions are atoms that can carry a charge and can change their charge by gaining or losing electrons. 

 Ions lay at the basis of all energy production inside the cell, which in turn is the foundation of life. Without energy you are dead and by upregulating energy production a biological organism can work more effectively/efficiently. 

Secondly, pulsing might affect the mitochondria directly. Mitochondria are the "powerhouses" of your cell, although they're also related to other functions such as the immune system and cell defence (10; 11; 12; 13).

The better your mitochondria work, the lower your overall risk of many chronic diseases is - except perhaps diseases that are genetic in origin. Red light therapy also affects these mitochondria directly, by making the final step of the energy-creation process in the mitochondria called "Cytochrome C-Oxidase" (COO) more efficient. That step is affected by Nitric Oxide (NO), and pulsing may affect that step differently from continuous wave red light therapy.

 

Caveats To Pulsed Red Light Therapy

Nevertheless, I don't want to state that these effects are proven beyond a reasonable doubt. Here are a few caveats to keep in the back of your mind regarding pulsing studies:

  • Medical-grade red light therapy uses mostly lasers and sometimes LEDs that are placed very closely on the skin. That way, you get far more power output and a higher penetration depth. Red light therapy panels used in homes use LEDs that are used at least a few inches off the skin. By using light that's not directly place on the skin, a lot of it is reflected, giving you a lower total dosage per unit of time.
  • Most red light therapy panels, including panels, belts, wraparound, and other methods, use LEDs, which are different from lasers. Most studies use LLLT (Low-Level Laser Therapy) which are somewhat different from LEDs. Nevertheless, other studies claim that LEDs and lasers are equally effective, if and only if dosing parameters are equal (14; 15).

In the next section, I'll explore some studies that compare non-pulsing red light therapy with pulsed red light therapy. That example will show you that pulsing really does have a biological effect.

 

Pulsing Red Light Therapy Versus Continous Wave Red Light Therapy Studies

In this section, I'll explore some of the different outcomes of pulsed versus non-pulsed red light therapy studies. This outcome will showcase that  pulsing does have an effect on (human) biology. However, I want to be clear that a lot more research is needed on this topic as well until we can define what exact parameters need to be used for the best results. 

So, until then, as Alex already stated in the past, red light therapy is somewhat dependent on trial and error strategies. In other words, you'll have to find out what dosing parameters and settings work best for you.

As for my approach, I randomly picked studies I came across that compared pulsing and non-pulsing red light therapy. One benefit I have over the epic review that was published in 2010 is that we're now a decade further in red light therapy research and that many new studies have come out on this topic (4). Hence, even though I probably don't have the methodological rigour of this review as I don't include all available research, some new research is nevertheless included that wasn't available at time of this review.

So let's dive deeper into red light therapy pulsing versus non-pulsing studies:

 

Study 1: LLLT And Primary Dysmenorrhea

A 2021 study investigated the effects of pulsed versus continuous red light therapy (16). The topic of the study is the decrease of pain during dysmenorrhea (severe menstrual cramps). Outcome: both pulsing and non-pulsing LLLT worked equally well for lowering pain. The following dosing parameters were used:

"Group (A) were treated with three pulsed HILT sessions every cycle for three consecutive cycles using a long pulse Nd:YAG laser from a LASERSIX ME 15W device (Sixtus italia srl) with pulsed emission 1,064 nm, peak power of 3 kW, energy density fluency from 810 to 1,780 mJ/cm2, pulse duration of 120–150 msec, and a duty cycle of 0.1%, with a frequency of 10–50 Hz. The total average energy of the pulsed HILT application was 620 J, administered in three phases, from supine lying position on suprapubic region=300 J, initial phase (fast)=100 J, intermediate phase=100 J distributed at 5 points, final phase (slow)=100 J, from prone lying position on lumbosacral region (paraspinal) between L4–S3=320 J, initial phase (100 J): RT side 50 J + LT side 50 J, Intermediate phase (120 J): RT side (60 J) 3 points + LT side (60 J) 3 points, final phase (100 J): RT side 50 J + LT side 50 J.

Group (B) received three LLLT sessions every cycle for three consecutive cycles (a gallium–arsenide diode (GaAs) laser (BTL-5818SLM) was used). The LLLT was applied with the dose of 6 J\cm2, power of 100 mw, area equal to 1 cm2, and a duration of 1:15 min for 15 points, from supine lying position, 5 points on supra-pubic region, and from prone lying position, 10 points over lumbosacral region on L4–S3, 5 points on each side" (16).

As you can see, the dosing parameters are somewhat complicated to break down, even for someone who is very familiar with the red light therapy and LLLT space. No statistically different effect was found between the two groups though.

Next up:

 

Study 2: Bone Nodule Formation In Rat Skull Cells

Next up, a 2003 study comparing pulsed and non-pulsed red light therapy in rat calvarial (skull) cells (17). Here, continuous waves were compared with 1 Hz, 2 Hz and 8 Hz pulsing. The study was an in vitro study, meaning that cell cultures were used. The cultures were derived from rat fetuses in this case.

The study outcome was that all treatment parameters - so continuous and all the pulsing options - led to increased stimulation of cellular proliferation, bone nodules (abnormal tissue growth such as tumors, although often benign), Alkaline phosphatase (ALP) activity and gene expression. ALP is an enzyme that plays a role in breaking down proteins. 

The surprising outcome, however, is that the 1 Hz and 2 Hz configurations stimulated these factors the most. Continuous and 8 Hz parameters did stimulate these factors but to a lesser degree. So, for bone formation in general, pulsing such as 1 Hz and 2 Hz might be more beneficial than continuous dosing.

Moving on:

 

Study 3: Neurological Deficits And Cell Damage In Rat Brains

A 2006 study checked different power outputs and continuous versus pulsing parameters on cell damage in rats' brains (18). Light was used at 808 nanometers. That light was used at:

"to deliver power densities of 7.5, 75, and 750 mW/cm2 transcranially to the brain cortex of mature rats, in either continuous wave (CW) or pulse (Pu) modes. "

In plain English, the light was emitted through the skull, "transcranially". Notice that an extremely high dose of 750 mW/cm2 is used, which is way higher than the normal 40-100 mW/cm2 maximal dose that's often advertized by red light therapy companies.

The outcome? Neurological tests and examination of the cells show no adverse effects on these dosing parameters. What's interesting is that at the very high 750 mW/cm2 dose, the continuous wave option caused damage while the pulsed option did not. The explanation for this difference is that the former causes tissue heating while the latter does not.

And there's more:

 

Study 4: Puled Red Light Therapy In A Patient With Scleroderma

A 2014 study investigated the effects of both continuous and pulsed red light therapy on scleroderma (19). A 940-nanometer laser was used. Scleroderma is a skin disease characterized by hardening and toughening skin and a whole range of different symptoms. 

Unfortunately, the study only included one participant - so it's a case-control study. The participant was treated 2-3 times per week for 13 weeks. The pulsed device was placed on one elbow during the study, while the continuous was placed on the other elbow, to differentiate between the effects.

The outcome of the study is as follows according to the abstract of the study:

"Efficacy assessments included inflammation, symptoms, pain, health scales, patient satisfaction, clinical global impression, and adverse effects monitoring. Considerable functional and morphologic improvements were observed after LLLT, with the best results seen with the pulsing mode. No adverse effects were noted. Pulsed LLLT represents a treatment alternative for osteoarticular signs and symptoms in limited scleroderma (CREST syndrome)." (19).

So, pulsing here once more has the best outcome. Of course, because it's a study with only one participant you'll want to have a better study setup to achieve higher statistical power. Without sufficient study participants, it's very hard to find useful statistically significant outcomes.

Next up:

 

Study 5: Traumatic Brain Injury In Rats

A 2011 study investigated the effects of continuous waves, 10 Hz pulsing and 100 Hz pulsing after a traumatic brain injury in rats (20). A 50% duty cycle was used and light was emitted at 810 nanometers. 

The outcome of the study is described in the abstract as follows:

"The 810-nm laser pulsed at 10-Hz was the most effective judged by improvement in NSS and body weight although the other laser regimens were also effective. The brain lesion volume of mice treated with 10-Hz pulsed-laser irradiation was significantly lower than control group at 15-days and 4-weeks post-TBI. Moreover, we found an antidepressant effect of LLLT at 4-weeks as shown by forced swim and tail suspension tests."

Again, a surprising outcome - or perhaps unsurprising after I've looked at a few studies. Once more, a low Hz pulsing option seems to work best. That outcome means that the 10 Hz pulsing frequency worked better than the 100 Hz pulsing and continuous output.

In the extremely well-written full text of the study, the researchers posit different explanations to explain these differences (21). One explanation is that the 10 Hz pulsing is better at affecting the brain as a whole because it accords with the Theta waves of 4-10 Hz used in the brain already.

The researchers state:

"Particularly relevant is the fact that oscillation of theta waves that have a prominent 4–10-Hz rhythm in the hippocampal region of all mammals previously studied [51], [52], [53]. The fact that the hippocampus is responsible for behavioral inhibition and attention, spatial memory, and navigation suggests that the significant neurological recovery observed with the PW 10-Hz laser treatment may possibly have resulted from the positive resonance between the pulsing frequency of the laser and the electrical activity of neurons in the hippocampus. In fact, the hippocampus is one of the regions to suffer brain damage in Alzheimer's disease, and a recent study showed that transcranial laser therapy using an 808-nm laser diode attenuated amyloid plaque development in the transgenic mouse model with mutant amyloid- precursor protein, implying the possible efficacy of this therapeutic strategy for Alzheimer's disease" (21)

Other explanations can be found in the full text of the study as well (21).

And then:

 

Study 6: Orthodontic Tooth Movement In Rats

A 2012 study investigated the effects of continuous and pulsed red light therapy on the speed of tooth movement after an orthodontic intervention in rats (22). The orthodontic intervention was aimed at the molars, the teeth in the back of the mouth. Rats have twelve molars in total, just like humans - six at the left side and six at the right side, whereby three are located at the bottom and three at the top of the mouth.

Fourty rats were used in total and these rats were subdivided among five groups. Here's the study setup according to the abstract:

"In Group I, the maxillary left first molars were irradiated with CW by a gallium aluminum arsenide (GaAlAs) diode laser source (830 nm, 180 mW, 3.6 J/cm(2), and 0.9 W/cm(2) for 4 sec at three locations for 3 consecutive days). In Groups II, III, and IV, animals were irradiated with PW at 2, 4, and 8 Hz, respectively (50% duty cycle, average power of 90 mW, 3.6 J/cm(2), and 0.45 W/cm(2) for 8 sec at three locations for 3 consecutive days). Group V served as the control (no irradiation). The movement distance was measured on days 3, 7, and 14." (22),

The outcome here was that there are no differences in the groups receiving the red light therapy. Hence, this is the first study out of six that doesn't find a difference between pulsing and non-pulsing red light therapy. To be more specific, red light therapy did help speed up the tooth movement after the orthodontic intervention. Translated to humans, this outcome could mean that you'll need to spend less time wearing braces to correct the position of your teeth, for instance.

Unfortunately, there was no free full text of the study available, so I couldn't dig deeper for the explanations the researchers give to explain this outcome.

Let's move on to study number seven:

 

Study 7: Tendon Injury Repair In Rats

Next up, there's a study on comparing continuous and pulsed red light therapy where tending healing was compared in rats (23). The rats were divided into seven groups. All rats except the ones from group one were injured to create tendon problems. Here's the exact outline of the treatment and injury received by all groups:

  • Group 1: no injury nor any treatment
  • Group 2: injury and no treatment - euthanized after eight days
  • Group 3: injured and continuous wave red light therapy - euthanized after eight days
  • Group 4: injured and pulsed red light therapy at 20 Hz - euthanized after eight days
  • Group 5: injured and no treatment - euthanized after 15 days
  • Group 6: injured and continuous wave red light therapy - euthanized after fifteen days
  • Group 7: injured and pulsed red light therapy at 20 Hz for the first seven days and 2 Hz after that - euthanized after fifteen days

For the treatment groups, the power output of the LLLT treatment is equal for all at 4 J/cm2. Several biomarkers of tendon repair were measured:

"Glycosaminoglycan (GAG) level was quantified by dimethylmethylene blue method and analyzed on agarose gel. Toluidine blue (TB) stain was used to observe metachromasy. CatWalk system was used to evaluate gait recovery. Collagen organization was analyzed by polarization microscopy." (23).

The following outcome resulted:

"The GAG level increased in all transected groups, except [Group 5]. In [Groups 6 and 7], there was a significant increase in GAG in relation to [Group 5]. In [Groups 3 and 4], the presence of dermatan sulfate band was more prominent than [Group 2]. TB stains showed intense metachromasy in the treated groups. Birefringence analysis showed improvement in collagen organization in [Gropu 7]. The gait was significantly improved in [Group 7]. In conclusion, pulsed LLLT leads to increased organization of collagen bundles and improved gait recovery."

If you can decipher the complicated scientific language, you can observe that the pulsed red light therapy group that used a 20 Hz and 2 Hz frequency did best overall. So, the pulsed group had a better outcome than the continuous wave.

Next up, I've got one pulsed red light therapy study that I got straight from the excellent GembaRed website. I wanted to analyze the studies myself without reading GembaRed's conclusions so here we go:

 

Study 8: Transcranial Pulsed Versus Sham Control In Human Subjects

This study is actually tied to the Vielight red light therapy device (24; 25). The Vielight (code ALEX10 saves you money) is used through the nose so that the light can travel through the blood-brain barrier and on the skull. The LEDs on the skull are directly placed on the skull so that you'll have maximal penetration. Remember that it's harder to penetrate the skull because of the bone in between the brain and the LEDs. The Vielight Neuro Gamma model was used.

The control group in the study received a sham intervention. A sham intervention is not real, so technically, this study doesn't investigate continuous versus pulsed waves. However, the researchers wanted to know whether brainwave entrainment occurs with this treatment model. Light was used at 810 nm and 40 Hz. electroencephalography (EEG) was used to measure the alpha, beta, gamma, theta and delta waves of the brain.

After one week, the participants of the sham intervention received the real intervention and vice versa. A total of 20 human participants were included. 

The study has the following results and conclusion:

"we found that a single session of tPBM [transcranial Photobiomodulation (LLLT)] significantly increases the power of the higher oscillatory frequencies of alpha, beta and gamma and reduces the power of the slower frequencies of delta and theta in subjects in resting state. Furthermore, the analysis of network properties using inter-regional synchrony via weighted phase lag index (wPLI) and graph theory measures, indicate the effect of tPBM on the integration and segregation of brain networks. These changes were significantly different when compared to sham stimulation. Our preliminary findings demonstrate for the first time that tPBM can be used to non-invasively modulate neural oscillations, and encourage further confirmatory clinical investigations." (24).
 

In short, pulsed red light therapy can induce brainwave entrainment.

Alpha, beta and gamma brainwaves were stimulated while theta and delta were inhibited. Also, different parts of the brain are be activated, such as the "default mode network" associated with introspection. Wakefulness can also be stimulated in this way, potentially. As the study states, stimulating these higher-frequency brainwaves such as beta and alpha may help with Alzheimer's and dementia. Memory consolidation and the prevention of neurotoxicity may also result.

Overall, I'd like to have seen a comparison between pulsing and continuous waves for an even better understanding of what's happening with the pulsing frequencies.

Next up:

 

Study 9: Pulsed Versus Continous Lasers For Wound Healing In Rats

In this study, 67 rats were given second-degree burns on their skin (25). The rats were then divided into four groups:

  • Group 1: regular laser treatment (placebo)
  • Group 2: pulsed laser treatment at 2.3 J/cm2 at 3,000 Hz
  • Group 3: pulsed laser treatment at 11.7 J/cm2 at 3,000 Hz
  • Group 4: pharmaceutical intervention of 0.2% nitrofurazone which was applied on the skin

Result? Group three had the best outcome in this case, so the higher pulsing parameters. The occurrence of Staphylococcus aureus, a bacterium that can be harmful in certain situations, was improved most in group three. Wound closure was also statistically significantly enhanced compared to the placebo group.

Overall, another nice outcome. Moving on:

 

Study 10: Another Wound Healing In Rats Study - A Win For Continous Waves

A 2004 study compared the effects of different pulsing parameters and continuous waves on wound healing in rats (26). A 635 nm laser was used. The groups receiving the pulsed red light therapy were subdivided into 100, 200, 300, 400, and 500 Hz. Then, the relative wound healing was measured for all the rats.

The outcome is as follows:

"The percentage of relative wound healing was 4.32 in 100 Hz, 3.21 in 200 Hz, 3.83 in 300 Hz, 2.22 in 400 Hz, 1.73 in 500 Hz and 4.81 in CW." (26).

So, overall, a lower pulsing frequency worked better than the higher pulsing frequencies. Also, the continuous waves had the best overall outcome.

Unfortunately, no low pulsing frequencies were included, such as 2 Hz, 40 Hz, and others that were seen in earlier studies that I've covered previously. I'd love to see how these lower pulsing frequencies stack up to continuous red light therapy. Fortunately, that dream is about to come true in the next study. So, one more wound-healing study in rats:

 

Study 11: Wound Healing In Immunosuppressed Rats

A 2016 study investigated the effects of continuous waves versus pulsing in immunosuppressed rats (27). An 810 nm laser was used, both continuously and under 10 Hz and 100 Hz. The dosages are (40 mW/cm2 for a total dose of 22.6 J/cm2. A pharmaceutical called "hydrocortisone" was used to make the rats immunosuppressed. The researchers then measured many different biomarkers for wound healing. 

The results of the study are as follows, according to the abstract of the study:

"Results clearly delineated that 810 nm [PhotoBio Modulation (PBM)] at 10 Hz was more effective over continuous and 100 Hz frequency in accelerating wound healing by attenuating the pro-inflammatory markers (NF-kB, TNF-α), augmenting wound contraction (α-SM actin), enhancing cellular proliferation, ECM deposition, neovascularization (HIF-1α, VEGF), re-epithelialization along with up-regulated protein expression of FGFR-1, Fibronectin, HSP-90 and TGF-β2 as compared to the non-irradiated controls. Additionally, 810 nm laser irradiation significantly increased CCO activity and cellular ATP contents. Overall, the findings from this study might broaden the current biological mechanism that could be responsible for photobiomodulatory effect mediated through pulsed NIR 810 nm laser (10 Hz) for promoting dermal wound healing in immunosuppressed subjects." (27).

In plain English, the 10 Hz dosing parameter worked best for many different biomarkers associated with wound healing, such as circulation, inflammation, energy production, mitochondrial stimulation, and more.

 

I'm very happy with this study outcome, showing that pulsing can have benefits once more. Although, as usual, the perfect pulsing and dosing parameters are hard to exactly define as so much is unknown still.

The full text of the study, however, does state that other previous studies have found similar results regarding pulsed versus continuous red light therapy with regards to some biomarkers (28).

 

Study 12: Root Resorption (Tooth Dissolution) After An Orthodontic Intervention In Humans

A 2018 study investigated the effects of either pulsed or continuous red light therapy on "root resorption" after an orthodontic root resorption intervention (29). Twenty study participants had their first molar removed and then received red light therapy or a placebo intervention. "Root resorption" is when a tooth is removed from the body, and your immune system subsequently restructures the area around the tooth (the root).

In total, 20 participants were included in the study for a total of 40 premolar teeth. 20 premolars received the sham intervention among the 40 participants. The other 20 premolars received red light therapy, from which ten received a continuous wave and ten a pulsed wave at 808 nm. Treatment time was 9 seconds for the continuous wave and 4.5 seconds for the pulsed wave.

The outcome was the following:

"LLLT resulted in 23 per cent less root resorption compared to the placebo (P = 0.026). Pulsed laser delivery resulted in 5 per cent less root resorption than continuous; however, this was not statistically significant (P = 0.823). No harm was observed." (29).

So, here, the pulsed group did slightly less well than the continuous group although the difference was not statistically significant.

 

 Study 13: Activation Of Mast Cells In Rats With Different Dosing Parameters

Next up, a 1996 study assessed the effects of different pulsing frequencies on mast cell activation and compared them with a sham laser intervention (30). Different pulsing frequencies, at 2.5 Hz, 20 Hz, 292 Hz, and 20,000 Hz were used. 800 mW/cm2 was used as the power density at the tissue level, for a total dose of 21.6 J/cm2.

The outcome was that all of the laser interventions worked better than the sham intervention when looking at the degranulation of mast cells, but not their numbers. However, only the 20 Hz and 292 Hz reached statistical significance compared to the sham intervention. 

Lastly, the reason mast cells are activated in this study is that they will have downstream effects on wound healing. That way, tissue repair can be accelerated.

Once more, you can observe that pulsing does have an effect. The effect is not huge but it nevertheless exists.  

 

Study 14: Pulsed Versus Continous In Mice WIth Traumatic Brain Injury

One more study regarding traumatic brain injury, this time a 2012 study in mice (31). The researchers attribute the following benefits to red light therapy:

"Many interacting processes may contribute to the beneficial effects in [Traumatic Brain Injury (TBI)] including neuroprotection, reduction of inflammation and stimulation of neurogenesis. Animal studies and clinical trials of transcranial-LLLT for ischemic stroke are summarized. Several laboratories have shown that LLLT is effective in increasing neurological performance and memory and learning in mouse models of TBI. " (31).

The researchers carried out 3 studies on mice in their laboratory. One study found that 10 Hz pulsing is superior to a continuous wave. They also found that 660nm and 810nm work well for TBI, but not 760 and 960nm.

 

Study 15: Skeletal Muscle Inflammation In Rats: Pulsing Versus Continous

Lastly, a study that investigates many different parameters of red light therapy on skeletal muscle inflammation - specifically the calves (gastrocnemius muscle) - in rats (32). Continous light was used at 830nm and 980nm, and pulsed at 830nm. Per wavelength, animals were divided into different groups. These different continuous groups received different dosages, so 10 mW, 20 mW, 30 mW, 40 mW, 50 mW. A control group also existed.

Red light therapy was applied for five days straight. In the pulsing group, different frequencies were used. Pulsing frequencies of 5 Hz, 25 Hz, 50 Hz, 100 Hz and 200 Hz were used. The pulsing groups only received a 40 mW dose, no different ones.

Here's the outcome of the study:

"For continuous irradiation, treatment effects occurred for all doses, with a reduction of TNF-α, IL-1β, and IL-6 cytokines and inflammatory cells. Continuous irradiation at 830 nm was more effective, a result explained by the action spectrum of cytochrome c oxidase (CCO). Best results were obtained for 40 mW, with data suggesting a biphasic dose response. Pulsed wave irradiation was only effective for higher frequencies, a result that might be related to the rate constants of the CCO internal electron transfer process." (32).

 So, this time, continuous waves were superior to pulsing overall. The full text of the study is quite complicated but offers a more complete explanation if you're interested (33).

 

My Analysis: Does Red Light Therapy Pulsing Work? And Is Red Light Therapy Pulsing Better Than Continous?

So, what's the outcome of these 15 studies that I've analyzed?

My final viewpoint is that there's certainly something to pulsing, although it's tough to establish what parameters you need to use. In other words, it's still very much unknown how to precisely apply pulsing. There seem to be some (if not many) underlying variables that are currently undiscovered, that predict whether pulsing gives you superior results in treatment or not.

Sure, the effects of red light therapy pulsing are very unpredictable. And, most if not all of the pulsing research is carried out with lasers right now, not with LEDs. But my counterargument to the latter argument is that it's more likely that pulsing effects using LEDs are similar to those with lasers. Of course, that thesis needs to be tested and right now it isn't.

So let's consider the quotes I included at the start of this blog post:

First, the quote from Red Light Therapy At Home website:

"pulsing in red light therapy does not add to its therapeutic benefits" (1).

Then, PlatinumLED states:

"While using pulsed led light has become something of a trend, don’t fall for this flashy new application method. It was created for the world of laser therapy, and that’s where it should stay. If you’re using an LED panel, continuous, steady usage will yield the best results." (2)

And lastly, the GembaRed website reads:

"So if a company is advertising pulsed red light therapy for some special medical application or benefit, then be wary!

If the pulsing is a designed to mitigate heating or transcranial application for entrainment then that would be practical and acceptable.

But if companies like Joovv are just adding pulsing to their long list of gimmicks and making extra medical claims, then make sure to dig into the science yourself." 
(3).

(Removed bold emphasis in the text above)

I disagree here in that red light therapy doesn't have a therapeutic effect - it certainly has. However, I do agree with these companies' statements in that most people shouldn't bother finding the exact best pulsing frequency for their goals. Studies show that both continuous waves and pulsing frequencies work, and hence, you don't need to overcomplicate your red light therapy sessions.

But, to say that there's no therapeutic value cannot be concluded either, from the research. We need more studies using pulsing with LEDs specifically to be able to conclude that.

Also, a lot of research that I've seen in the 15 studies I've quoted above seem to conclude that the lower pulsing frequencies are best overall. Pulsing frequencies like 1 Hz, 2 Hz, 10 Hz and 20 Hz sometimes show positive results.

Next up, I do want to say that my methodological quality of randomly picking 15 pulsing studies isn't perfect. For the best results, you'd want to scan medical databases like PubMed, Embase, and others exhaustively for all continuous waves versus pulsing studies and then compare all the available data. Due to time constraints and not wanting to spend many weeks on this topic, I've chosen my current methodology. A full review of all the available data on this topic could thus lead to a slightly different conclusion. 

Lastly, I do want to say that you've got nothing to lose by experimenting with pulsing. If you do use pulsing, make sure to wear protective glasses though that don't expose your eyes to the extremely intense on/off stimuli that can trigger fatigue or even epileptic attacks in some. Only expose your body to the pulsed red light therapy, never your eyes. I do hope though that by testing some different pulsing frequencies we'll find out more about it's effects. Maybe some people will find changes in how they recover from workouts, by using a low pulsing frequency combined with a very high power output, for instance. Or maybe you'll find out that you've got other benefits from using pulsing frequencies. Just let me know about your findings in the comments.

Next up, I want to consider some of your best options for red light therapy pulsed panels if you're going to use pulsing anyway:

 

Best Pulsed Red Light Therapy Panels

If you're looking for a good pulsed red light therapy panel option, then there are three options:

  • The Mito Red MitoADAPT panels that have a pulsing function from 1-9,999 Hz. These panels emit 630, 660, 810 and 850 nm light. The LEDs are dual-chip which means you can choose from different configurations of the light and put an emphasis on different wavelengths. For instance, you can use 810nm light exclusively in the near infrared range, and the 630 and 660 too, meaning that you disable the 850nm emissions. Many different modes are offered with this panel. If you want to learn more, check Alex's preview of the MitoADAPT 2022/2023 red light therapy devices on YouTube.


    (Mito Red MitoADAPT panel, the MitoMID displayed here. Code ALEX saves 5% if you click THIS link)


  • The LIghtpath LED Multiwave Pulsed that also has a 1 Hz - 9,999 Hz pulsing frequency options. This panel also offers so-called "Nogier frequencies" which are argued to have specific effects by the founder of LightpathLED Scott Kennedy. If you're interested in learning more, check out Alex's YouTube review of the LightpathLED Large Multiwave Pulsed and his interview with LightpathLED founder and owner Scott Kennedy.

    Pulse Series
    (LightpathLED Multiwave Pulsed Tabletop And Large panel displayed - code ALEX saves 5% if you click THIS link)
  • The Infrardi Flex series offers pulsing between 1 Hz and 9,999 Hz (or to be more precise 10,000 Hz in this case). Also, this panel emits five wavelengths, 630 nm, 660 nm, 810 nm, 830 nm and 850 nm. Alex has reviewed the Infraredi Flex Max on YouTube - his assessment is quite positive. The previous Infraredi Max also placed third in his body comparison series of 2021/2022, and this Infraredi Flex series is a better update of that, so the outcome is really great here.


    (Infraredi Flex Mini, Mid and Max displayed - code ALEX saves 10% if you use THIS link).


There's also the Joovv Solo 3.0 but I don't recommend that option because its value proposition is actually quite poor and you only get one pulsing option, not the full spectrum of options. Check out Alex's YouTube review of the Joovv Solo 3.0 if you want to know why.

Nevertheless, it's hard for me to choose a panel between the Infraredi Flex Max, the LightpathLED Large Multiwave Pulsed, and the Mito Red MitoADAPT panels, in part because Alex also needs to compare them still. All three are amazing panels though that will work and will give you results. The best thing about these panels from these red light therapy series is that you can configure your own pulsing frequencies and therefore mimic any of the outcomes of the studies that I've treated above.

Finally, let's conclude:

 

Conclusion: The Pulsing Science Is Complicated But There Is An Effect For Sure

Right now, there's insufficient evidence to use red light therapy pulsing in a widespread fashion, at least with LEDs. But certainly, there's evidence available that pulsing has a definite effect. So, hopefully, in the future, we'll find out more about the mechanisms behind how pulsing exactly works and how it affects the effects of red light therapy on the cellular level.

If you're a real geek though and want to experiment, I recommend using some of the lower pulsing frequencies, such as 1 Hz, 2 Hz, 10 Hz, 20 Hz, and so forth. You could even align these frequencies with common brainwave entrainment frequencies that are used. Fortunately, there are some quite nice panels on the market right now where you can personally select the pulsing frequencies and experiment with them. All of these panels seem to be high-quality - Alex hasn't reviewed all of them yet so we can't say for certain right now.

Also, hopefully in the near future we'll see more high-quality research appear, not only with lasers but also LEDs, and more comparative studies using both continuous waves and pulsing options. With that research, you'd be able to better conclude and find out how pulsing works, what its effects are, and so forth.

In the meantime, I'll be keeping track of the latest developments of red light therapy pulsing and will be updating this article for you! And, stay tuned for more red light therapy science deep dives that will be coming up in the future. That future is bright, it seems! 

 

Items Mentioned:

 

 This is a post by Bart of team Alexfergus. Bart finished degrees in Physical Therapy (B), Philosophy (BA and MA), Philosophy of Science and Technology (MS - with distinction), and Clinical Health Science (MS), has had training in functional medicine, and is currently a health consultant at Alexfergus.com.   

 

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