One of the important issues in the application of red light therapy is the choice of continuous or pulsed light. Many of the treatments employed in biomedicine and physical therapy rely on the pulsed format.

Keywords:

photomedicine, health

Electrical currents, electromagnetic, magnetic fields and ultrasound are applied with particular pulse structures. Pulsed electromagnetic field therapy, for example, has been used for a variety of health conditions. The non-exhaustive list includes bone healing and soft tissue regeneration, wound healing, osteoporosis, arthritis, different pains, nerve regeneration, even cancer.

In spite of the existence of some degree of agreement as to the best and most efficient wavelengths and recommended pattern of use, there is still an open question whether the application and efficiency of continuous light (CL) and the pulsed light (PL) yield comparable results or there are advantages in using one over the other. The effects need to be compared on the cellular, molecular and tissue levels. Also, the optimal pulsed light parameters including the frequency need to be determined in order to achieve the best therapeutic results.
There are several different mechanisms to generate light in a pulsed as opposed to continuous mode and they differ in terms of pulse frequencies and energies, neglecting for this exposition other less important differences. When pulsed light is applied with lasers, then the clear advantage of the pulsed light is due to the safety issues. Namely, the continuous light increases temperature of the target tissue while the pulsed light, at the same energy, causes no significant change in the temperature of the irradiated tissue. However, when the light is administered with LEDs, the differences are more subtle.

The pulse frequency refers to the interval between the time when the light is on to the next “on” time. This is measured in units of Hertz, or Hz, which is simply the cycles per second. For example, pulse frequency of 10 Hz means that the light is flashing on and off 10 times per second. With pulsed red light therapy there is typically a “duty cycle” of 50%, which means there is an equivalent amount of time in the “on” position and “off” position. This also means that compared to continuous wave, a pulsed light will have an average intensity of half of the continuous.
There may be several biochemical reasons for the improved efficacy of pulsed light over continuous light. Pulsed light sources, including both lasers and LEDs, have frequencies in the 2.5–10,000 Hz range and pulse durations are often in the range of a few millisecond. The improved effects of the pulsed light as compared to the continuous one may be due to the fact that the frequencies in the range of tens to hundreds or thousands of Hz are characteristic for certain organs or tissues or that there are some processes on the time scale that corresponds to these frequencies.

One of the most important reasons for this effect is that the electromagnetic waves generated by the human brain have specific frequencies that influence all other processes in the body. Electroencephalography recordings distinguish four classes of brain waves. Alpha waves (8–13 Hz) occur in the relaxed state of adults. Beta waves (14–40 Hz) mainly occur when the individuals are alert or focused. Delta waves (1– 3 Hz) occur mainly in infants, during deep sleep of adults. Theta waves (4–7 Hz) occur mainly in children ages 2–5 years old and in adults in the meditative states or in the state between waking and sleeping. Thus, the occurrence of resonance between the frequency of pulsed light and the frequency of brain waves may enhance the therapeutic effects. This is particularly relevant for the Lucha t8 device, since the pulsating frequency is 7.83 Hz, at the border of alpha and theta waves.

The second effect is related to the results obtained in several studies related to the functioning of ion channels in cellular activity. Namely the cellular membrane may be an ionophore for different types of ions and for differently charged ions of the same type. For example, there are cellular pores (channels) that permit traffic solely of positively charged ions (cations) and there are channels that permit only negatively charged ions (anions) to exit or enter the cell. These ions can move freely across the cell membrane however, in some ion channels the pore has a “gate” type entrance that requires a “key” to enter. The “key” is a certain type of chemical or electric signal, temperature or mechanical force, depending on the ion channel and the cell. Voltage-activated ion channels are particularly important in transmitting impulses through the nervous system. In general, the time scale of opening and closing the ion channels is of the order of few milliseconds. Potassium and calcium ion channels in the mitochondria are also very important since there is some evidence that they may be involved in the cellular response to the red light.

The third effect of action of red light on a cellular level is the photodissociation of nitric oxide from a protein binding site of a cytochrome c oxidase. The nitric oxide can rebound to the same site even in the presence of continuous light, however in the presence of pulsed light the number of dissociations is much smaller.

As mentioned earlier, the most important parameter that governs the depth of penetration of LED (and laser) light into tissue is wavelength. Both the absorption and scattering coefficients of living tissues are higher at lower wavelength so near-infrared light penetrates more deeply than red, red more deeply than green etc. One of the interesting issues related to the light irradiation of the human skin is the comparison of the penetration depth of the pulsed vs. continuous light. Some calculations and experiments confirm that smaller penetration depth can always be compensated by longer exposure, so that the comparison is not crucial for the application purposes.

Also, many effects important and beneficial from the medical aspect do not depend on the penetration depth. A more important issue is the choice of wavelength which yields the best therapeutic and healing effects. This aspect requires extensive experimental procedures and data comparisons and also involves the patient’s biochemical characteristics as an important factor determining the success of the therapy. Thus there are many parameters that determine the optimal choice, so results usually differ from one study to the other. For example, frequencies in the range from 20 to 3000Hz were administered and each study found a different frequency which promoted wound healing. A similar situation occurred in the studies of photobiostimulation effects on pain attenuation. Numerous studies demonstrated the beneficial effects of LED light therapy for the treatment of various pathologies at various frequencies. Some of the improvements include peripheral nerve regeneration, reduction of inflammatory reactions, enhancement of bone formation and as of recently, the promotion of angiogenesis, the formation of new blood vessels out of pre-existing ones has been demonstrated.

Although there are many promising results and a number of studies showing the undisputable beneficial results of the red light therapy, there still remains a lot of additional clinical research to compare its efficiency in comparison with the currently existing therapies for treating various pathologies and minor health conditions.

At the moment, the beneficial effects of red light therapy have been recorded for the following conditions:

Promotes tissue repair and wound healing through decreasing inflammation

Red light therapy can considerably lower inflammation levels in the body implying that it can be used to treat problems like medium to excessive swelling, osteoarthritis and joint injuries without any of the side-effects that are commonly associated with inflammation-reducing non-prescription drugs such as non-steroidal anti-inflammation drugs (a.k.a NSAIDs).
The best results are obtained when this therapy is performed along with the prescribed physical exercise. One of the reasons for this effect is that the red light therapy increases tissue and muscle blood flow. The efficacy of red light therapy for reducing inflammation has been experimentally demonstrated on many parts of the human body such as the limbs, back, neck etc., so that even a small therapy device, for example using one LED, can be used to treat a particular area of the body. Many widespread ailments, such as cardiovascular disease, obesity, diabetes and cancer are all accompanied with considerable inflammation levels, although not caused by them.

Improves functioning of thyroid hormones

Red light therapy can increase thyroid hormones which are important in the regulation of the energy production in the human body. In particular, the red light therapy can actually improve hypothyroidism conditions through application for longer periods of time although first signs of improvement may be discernible within several days of daily application. Thyroid function also affects production of steroid hormones such as testosterone. Optimal testosterone levels are not only important for men, but also for women. Testosterone in women is linked to sex drive, energy and general well-being. In women, testosterone is produced in the ovaries while and men’s testicles.

Enhances blood circulation

The penetration depth of red light is sufficient to reach the blood vessels so that the light can enhance blood circulation, even in the smallest blood vessels. Red light therapy also helps in creation of new blood vessels. Good blood circulation is important for proper oxygen transportation, delivery of nutrients in all parts of the body and removal of toxic waste.
Improves and boosts fertility

In men, red light therapy can improve semen volume, its movement, and endurance. Red light therapy can also help men with erectile dysfunction due to its effects on the improvement of blood flow. It increases the amount of carbon dioxide (CO2) in the blood which helps carry more oxygen in the blood and expands blood vessels. Thus CO2 is not just a waste product in the body. The other mechanism involves nitric oxide explained earlier. Several studies showed that in women, almost 25% of severely infertile women conceived after therapy suggesting that even better results may be possible for less severely infertile women.
Improves functioning of the immune system

Red light can stimulate the thymus gland located in the chest. Thymus is essential for the proper functioning of the immune system but its influence diminishes with age which can be slowed down with the application of the red light therapy. Secondly, red light therapy increases the activity of several immune system cells, such as macrophages which are in the first line of defense against infections which clean up dead cells. The effects on dendritic cells, which have messaging function, are less known and require more studies in order to learn their response to red light therapy. Mast cells, a specific type of white blood cell, are significantly increased by red light therapy. Their function is to create fibrous material in wound healing. Finally, red light therapy has beneficial effects on leukocytes (a.k.a. white blood cells) and lymphocytes. The former protect the body against disease by ingesting foreign materials and cellular debris and by destroying infectious agents. The latter are important in detoxification and for destroying bacteria in the blood.

Improves eye health

The eyes have very high energy demand relative to the energy demands of the tissue of the same size and the boost in energy production due to the red light therapy has an important effect on eyes and eye sight. Beneficial effects have been noticed in treating age-related macular degeneration, cataracts and dry eye problems (meibomian gland disfunction).

  • Stimulates healing of slow-healing wounds such as diabetic foot ulcers
  • Reduces psoriasis lesions
  • Aids with short-term relief of pain due to the rheumatoid arthritis
  • Reduces some of the side effects of cancer treatments. It’s important to note that when red light therapy is used with cancer treatments, the light is only used to activate another medication.
  • Improves skin complexion and promotes collagen generation
  • Diminishes wrinkles
  • Helps to elevate damage from excessive exposure to UV sun rays
  • Prevents recurring cold sores from herpes simplex virus infections
  • Improves the health of joints in people with degenerative osteoarthritis of the knee
  • Helps diminish scars
  • Relieves pain and inflammation in people with pain in the Achilles tendons
  • Improves hair growth in people with androgenic alopecia