LED treatment
Light, and what tissue does with it
Light carries energy, and certain wavelengths of red and infrared light can pass through the skin and coat and be absorbed by the tissue beneath. Once absorbed, that light can influence biological processes within the cells, which is the basis of photobiomodulation.
Unlike treatments that introduce a substance into the body, LED treatment works through the energy delivered by the light itself. What happens afterwards depends on how the tissue responds to that energy.
The principles are relatively straightforward, but the biology behind them is more complex. On this page, we look more closely at what happens when red and infrared light reaches tissue, what research has shown so far, and where the current evidence still has limitations.
The mechanism
What the light is actually absorbed by
Almost every cell contains mitochondria, the structures responsible for producing energy in the form of a molecule called ATP, and current understanding is that red and infrared light acts at this level. Where more energy is available to a cell, the processes it already carries out can proceed more readily, so the light is not introducing a new mechanism so much as supporting one that is already running.
The research base is substantial but uneven. Most of it comes from human and laboratory work rather than equine studies, findings frequently conflict because wavelength, dose and duration vary so widely between trials, and several of the strongest equine studies have used lasers rather than LEDs. A 2023 systematic review covering horses, dogs and cats found conflicting results and a high or moderate risk of bias across the papers it assessed, and we set out the individual studies, including those that found no effect, on our research page.
Why we rarely use the word photobiomodulation
The name given to this in the literature is photobiomodulation. It is a term that explains relatively little on its own, so we use it sparingly, although it is the word to search for if you want to read the underlying research.
Which part of the cell actually absorbs the light
The best-supported explanation is that cytochrome c oxidase, an enzyme within the mitochondrial respiratory chain, absorbs red and infrared light directly, and that this absorption increases electron transfer along the chain so that more ATP becomes available. Light-sensitive and heat-sensitive ion channels in the cell membrane are understood to provide a second route, although the relative contribution of each is not fully established.
The optical window
Why the systems work in red and infrared
Between roughly 650 and 950 nm there is a band in which blood, pigment and water all absorb relatively little, and light is able to travel further into tissue. This band is generally referred to as the optical window, and it is the reason that treatments intended to reach tissue below the surface use red and infrared light rather than shorter wavelengths. It is also why our systems contain no blue light.
Why blue and green light stops at the surface
Tissue is not equally transparent to all wavelengths of light, because different substances within the body absorb light at different points in the spectrum, and that absorption determines how far a photon can travel before it stops.
Below roughly 650 nm, haemoglobin and melanin absorb strongly, so blue and green light is taken up almost immediately at the surface and does not reach muscle, tendon or joint. Above roughly 950 nm the position reverses and water begins to absorb heavily, converting the energy to heat before it travels any useful distance.
The second reason we left blue light out
There is a further consideration with blue light, in that published laboratory work has shown bacteria can develop resistance to repeated exposure at 405 nm. Neither point would be decisive in isolation, but taken together they were sufficient to settle the question for us.
Absorbed by blood and pigment
The optical window
Absorbed by water
Wavelengths
Four wavelengths, four depths
Coat surface
0 cm
660/670 nm
1–2 cm
730 nm
2–3 cm
810 nm
3–4 cm
850 nm
4–5 cm
Each wavelength reaches a different depth, which is why every LED by CHEVAL system carries four rather than one. Two types of LED strap alternate across each system, one emitting red light at 660/670 and 730 nm and the other infrared at 810 and 850 nm, and both types are present in every system we make.
| Wavelength | Type | Approximate depth | Associated with |
|---|---|---|---|
| 660/670 nm | Red, visible | 1–2 cm | Wound healing, tissue repair, circulation, reduced inflammation |
| 730 nm | Red, visible | 2–3 cm | Reduced inflammation, pain relief, collagen and tissue regeneration |
| 810 nm | Infrared, invisible | 3–4 cm | Deeper muscle, tendon, and joint. Oxygenation |
| 850 nm | Infrared, invisible | 4–5 cm | Pain relief, circulation and fluid balance, swelling, deep tissue |
Infrared is invisible. The 810 and 850 nm straps will not appear to glow, even though they reach the greatest depth of the four, so the alternating infrared straps look dark while the system is running normally. This is the question owners ask us most often, and in almost all cases the system is working as intended.
Why these four wavelengths and not others
The wavelengths were not selected arbitrarily. Most photobiomodulation research has concentrated on two bands, roughly 630 to 670 nm and roughly 780 to 850 nm, and our 660 and 670 nm fall within the first while 810 and 850 nm fall within the second. The 730 nm strap sits between the two bands and was chosen for the depth it reaches rather than for the weight of literature behind it. Cytochrome c oxidase has separately been described as having absorption peaks near 620, 680, 760 and 820 nm, which is the same region of the spectrum that our four wavelengths occupy.
Why we call these depths typical rather than guaranteed
These should be read as typical rather than guaranteed, since penetration depends on what lies in front of the light, and a clipped summer coat over a cannon bone presents considerably less than a thick winter coat over a hindquarter. We publish the figures because they represent a reasonable general case, not because light stops at a measured line.
Dose
What the output figures mean, and why more is not better
Output figures are quoted widely in this category and rarely explained, so it is worth setting out what ours refer to and how they were arrived at.
The difference between irradiance and dose
Irradiance describes how much light arrives per unit of area at a given moment and is measured in mW/cm², while dose is that irradiance multiplied by the duration of the session and is measured in J/cm². The two are easily confused, and a high irradiance held for a short period can deliver the same dose as a lower one held for longer.
Ours, measured with a TES 1333 solar power meter at a distance of 1 cm:
| Irradiance | ||
|---|---|---|
| Infrared straps (810 / 850 nm) | ~19.8 mW/cm² | 197–199 W/m² |
| Red straps (660 / 670 / 730 nm) | ~10.4 mW/cm² | 104 W/m² |
| Both strap types together | ~30.2 mW/cm² | ~302 W/m² |
Because both strap types operate simultaneously, the figure relevant to dose is the combined one, which over five minutes gives approximately 9 J/cm² and over ten minutes approximately 18 J/cm².
Beyond a certain point, additional light stops adding benefit, which is why a longer session is not necessarily a better one and why a more powerful system is not necessarily a more effective one. It is also why lamp counts are a limited basis on which to compare two systems, since what reaches the tissue depends on irradiance and duration rather than on the number of diodes listed in a specification. Our systems are designed to operate at five to ten minutes per area.
Why more light stops helping after a point
Photobiomodulation is generally described as following a biphasic dose response, meaning that the relationship between dose and effect is not linear. Below a certain threshold there is no measurable effect, above it the effect increases until it reaches a plateau, and beyond that plateau the benefit declines again towards nothing, with the possibility of a negative effect at higher doses still.
Laser and LED
How LED differs from laser
Both laser and LED deliver red and infrared light and are understood to work through the same underlying mechanism, and what distinguishes them is the way the light is organised. Laser light is coherent, meaning that the waves are aligned and concentrated into a narrow beam, and that concentration accounts both for its power and for the requirement for eye protection and a trained operator.
LED light is non-coherent and distributed across many diodes, so there is no focused beam to direct and no eye protection required for either the handler or the horse. This is the practical distinction between a treatment that takes place as a professional appointment and one that can be carried out in the stable as part of an ordinary routine.
Why so much equine equipment is still called laser
There is a naming issue worth being aware of. Much of this field was historically described as low-level laser therapy, and a considerable amount of published work still uses that term. In 2016 an international consensus moved the terminology to photobiomodulation, in part because the word laser had become inappropriate as LEDs came into wider use. Equine systems are still frequently described as laser treatment, and in most cases this reflects the older terminology rather than the device being used.
In practice
Three things that change the result
A wet or dirty coat
A wet or dirty coat scatters and reflects light at the surface, so less of it reaches the tissue beneath. This is the most common reason a session delivers less than expected, and also the simplest to address, since brushing the area and allowing it to dry is usually sufficient.
Distance
Our figures are measured at a distance of 1 cm. The LEDs sit through cut-outs in the fabric rather than behind it, so there is no material between the diode and the coat, and the system rests against the horse rather than standing away from it.
Anything laid over the top
A blanket or cover placed over a system while it is running will trap heat, so the system should be left uncovered for the duration of the session.
Construction
How the systems are put together
Cut-outs rather than a covered panel. The LEDs sit through cut-outs in the fabric rather than behind it, so the light leaving the diode is the light that reaches the coat.
Both strap types, always. Red and infrared straps alternate across every system, and there is no model that carries only one of the two.
Built for a stable. Reinforced for the handling that equipment receives around horses, including being knocked, dropped and stood on.
What happens when a single lamp fails
Every lamp is connected to the next, so if one fails the lamps following it will also go out. The practical effect is that a fault becomes immediately apparent and its position is easy to identify, rather than presenting as a slightly dimmer section that could go unnoticed.
The limits
What LED treatment does not do
LED treatment is not a cure and we do not describe it as one. Where a horse is being treated for a specific condition it belongs within a plan agreed with your vet rather than in place of one, and it will not compensate for a saddle that does not fit, for work the horse is not yet ready for, or for a foot that requires attention from a farrier.
It also does not reach all tissue equally. The hoof capsule blocks light, so work around the foot is limited to the vascular and soft tissue at the coronary band and pastern rather than anything within the capsule itself.
We do not publish timelines. Horses and conditions vary sufficiently that any figure we offered for how quickly a change might be noticed would be closer to marketing than to information.
If your horse is pregnant, under veterinary treatment, or has an existing condition, speak to your vet before beginning. We can tell you precisely what the system emits, but whether it is appropriate for your particular horse is a question for them.
Where to start
Try it on your own horse
Renting allows you to start without committing to a purchase. There is no deposit and no minimum period, and up to three months of rent is credited towards the purchase price if you decide to keep the system. Available throughout the EU.