What is the principle behind laser treatment?
Laser therapy, or photobiomodulation, is based on the effect of red and near-infrared light on biological tissues at the cellular level. The effect is not based on heating the tissue, but on the interaction between light and light-sensitive structures within cells.
In light of current research, the effects of photobiomodulation are especially linked to cellular energy production, tissue physiology, the regulation of inflammatory responses, microcirculation and tissue repair processes.
Biological effects of light in tissue
In research literature, laser therapy is often referred to as photobiomodulation, or PBM. This means the biological effect of light in tissues. In practice, red and near-infrared light is absorbed by light-sensitive structures in cells and can influence cellular function.
Photobiomodulation should not be understood as heat therapy. Its key effect is not based on heating tissue, but on light participating in cellular-level regulatory mechanisms. Research on PBM has particularly examined its effects from the perspectives of mitochondrial function, ATP production, nitric oxide regulation, ROS signalling, inflammatory responses, microcirculation, tissue repair and nervous system pain modulation mechanisms.
This makes laser therapy biologically interesting, but also demanding in terms of dosage and treatment technique. The effect of light in tissue does not depend only on the power of the device, but on how appropriately the light reaches the target tissue.
Mitochondria and cellular energy production
Mitochondria are central to cellular energy production. One of the key biological targets of photobiomodulation is considered to be cytochrome c oxidase, which is involved in cellular respiration and ATP production.
ATP, or adenosine triphosphate, is the energy molecule used by cells. Cells need ATP for processes such as tissue repair, protein synthesis, muscle function, maintaining ion balance and regulating inflammatory responses.
Based on current research, the effect of photobiomodulation appears to be particularly relevant in stressed and damaged tissues. In these situations, supporting cellular energy balance may be biologically meaningful as part of the tissue’s normal repair processes.
Nitric oxide, microcirculation and tissue oxygenation
The effects of photobiomodulation have also been studied through the regulation of nitric oxide, or NO. Nitric oxide is involved in vasodilation, microcirculation, tissue oxygenation and the regulation of inflammatory responses.
From the perspective of microcirculation, PBM is often examined as part of the metabolic regulation of tissue. When tissue oxygenation and cellular energy production are part of the same biological context, the effect of light is not limited to one single mechanism.
This is also important in animal laser therapy. In practical treatment situations, the goal is not “the highest possible power”, but a biologically appropriate amount of light in the right tissue.
ROS signalling as part of tissue response
Photobiomodulation also affects the function of reactive oxygen species, or ROS signalling. ROS compounds are often viewed as harmful, but controlled ROS signalling also acts as a biological messenger in the body.
This type of signalling can participate in activating tissue repair mechanisms and cellular adaptation responses. In PBM, the essential point is therefore not one single pathway of action, but the combined effect of several cellular-level events.
The dose response in laser therapy is not linear
Photobiomodulation is known to follow a biphasic dose response. This means that the effect does not increase linearly as the dose is increased. Too small a dose may be biologically insufficient, an appropriate dose may produce the desired response, and too large a dose may even reduce the response.
For this reason, several practical factors affect the outcome of animal laser therapy:
- dosage, treatment frequency and treatment time
- treatment technique and quality of contact
- the optical properties of the tissue, coat and tissue depth
This is one of the most important practical principles of laser therapy. Successful treatment is not based on a single device specification, but on delivering the right type of light to the right tissue at a biologically appropriate dose.
Inflammatory responses and tissue repair
The effects of photobiomodulation have also been studied from the perspective of inflammatory response regulation. Research has described effects on cytokines, prostaglandins, NF-kB signalling and macrophage function.
These mechanisms are linked to how tissue responds to load, injury and repair processes. In addition, PBM has been studied in relation to fibroblast activation, collagen synthesis, angiogenesis, wound healing processes and muscle tissue recovery.
Current research supports the view that photobiomodulation is a real biological phenomenon whose effects are based on cell biology and tissue physiology. At the same time, in practical treatment situations it is important to remember that the response of an individual animal is always also affected by the animal’s condition, tissue characteristics, treatment implementation and the broader care plan.
What does this mean in animal laser therapy?
In animal laser therapy, the biological mechanism is always combined with practical tissue optics. Although the cellular-level effects of PBM are similar across mammals, the way light travels in tissue during treatment is affected by the size of the animal, tissue structure, coat, pigmentation, treatment area and treatment technique.
This is why laser therapy should not be assessed only on the basis of device power, laser class or a single wavelength. The same technical setting does not necessarily mean the same biological effect in a short-coated dog, a horse with a winter coat or a dark-pigmented animal.
In animal laser therapy, practical success is based on the overall treatment context: assessing the treatment area, choosing the appropriate treatment head, selecting the correct treatment time, using the right technique, ensuring repeatability and understanding how laser therapy relates to other care, rehabilitation or muscle care.
Summary
Laser therapy, or photobiomodulation, is based on the biological effects of light in tissues. Its key mechanisms include mitochondrial function, ATP production, nitric oxide regulation, ROS signalling, regulation of inflammatory responses and tissue repair processes.
The effect is not based on heating the tissue, and the dose response is not linear. Too small a dose may be biologically insufficient, while too large a dose may reduce the response. This is why successful laser therapy emphasises dosage, treatment technique, tissue characteristics and repeatability.
In animal laser therapy, the best practical outcome is built on the whole: the right type of light, the appropriate method of use and consideration of the animal’s individual characteristics.
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