An in-depth guide to light therapy, part 2 with Dr. Mark Cronshaw
Mar 1, 2025
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Join Dr. Mark Cronshaw, a leading expert in photobiomodulation, as he dives deep into the mesmerizing world of red light therapy. He explores the complexities of dosimetry, emphasizing how light intensity impacts outcomes. Hear his thoughts on the shift towards evidence-based light therapy, the intricate role of various wavelengths in human health, and the balance needed to avoid overheating during treatments. Dr. Cronshaw also challenges traditional beliefs about light's effectiveness and highlights the empowering potential of understanding these technologies.
Photobiomodulation (PBM) utilizes specific light wavelengths to interact with human biology, promoting healing and reducing inflammation.
Dosimetry in PBM is critical, as factors like wavelength, irradiance, and duration significantly influence treatment efficacy and tissue response.
The debate surrounding thermal effects in PBM reveals differing opinions on how heat can enhance or hinder therapeutic benefits during treatment.
Expanding the focus beyond traditional red and near-infrared light to include various wavelengths can optimize therapeutic outcomes in clinical applications.
Deep dives
Introduction to Photobiomodulation
Photobiomodulation (PBM) involves the interaction of light, particularly red and near-infrared light, with human biology to promote healing and reduce inflammation. This episode discusses emerging lines of research and debates within the PBM community, highlighting the significance of understanding the complexities around dosimetry, which refers to how light is delivered and its impact on biological systems. Dr. Mark Cronshaw, a leading expert, emphasizes the distinction between evidence-based and eminence-based thinking in science, urging for a reevaluation of established ideas in favor of newer research findings. He explores how the understanding of PBM can evolve as researchers challenge traditional views based solely on historical precedent.
The Spectrum of Light and its Biological Effects
Light interacts with biological systems through various mechanisms, including photochemical, photothermal, and photoelectric effects. The impact of different wavelengths on cellular functions is central to PBM, with red and near-infrared light historically gaining prominence due to early research. However, Cronshaw argues that many wavelengths can produce beneficial effects, suggesting that different light sources should not be dismissed solely based on historical usage or assumed efficacy. He notes that understanding how various wavelengths affect different tissue components is crucial for optimizing PBM applications in clinical settings.
Understanding Dosimetry in PBM
Dosimetry, the study of how light energy is dosed in PBM, is multifaceted and influenced by various factors such as wavelength, irradiance, and treatment duration. Cronshaw explains that photons carry different amounts of energy based on their wavelength, which significantly affects how they interact with tissues. Effective dosage combines the intensity of light (irradiance) with the time of exposure, influencing cellular responses and the efficacy of treatments. He emphasizes the importance of precise dosimetry in ensuring therapeutic benefits without causing damage, as excessive irradiance can lead to unwanted thermal effects.
Controversies in PBM: Heat vs. Therapeutic Effects
The debate around PBM often includes the role of heat in therapeutic benefits. While some argue that PBM should be non-thermal to avoid tissue damage, others believe that a small amount of warming can enhance healing by improving blood flow and reducing pain. Cronshaw discusses the viewpoints of various experts, noting that some believe heating above certain thresholds can deactivate protective mechanisms in cells, potentially leading to harm. However, he posits that careful modulation of heat, particularly at low levels, can actually support the healing process rather than hinder it.
The Role of Wavelength in PBM Efficacy
The historical focus on specific wavelengths like red and near-infrared light in PBM research has led to a perception that these are the 'magic' wavelengths for therapeutic effects. However, Cronshaw argues that other wavelengths can produce similar biological outcomes when appropriately dosed. He highlights research demonstrating that shorter wavelengths, like blue light, can also benefit certain cellular reactions, suggesting the need for a broader perspective on light therapy. This expanded view encourages exploration of various light types and their therapeutic capacities rather than rigid adherence to traditional wavelengths.
Clinical Applications and Practical Guidance
In clinical settings, the practical application of PBM devices must consider the complexities of dosimetry and individual patient needs. Cronshaw stresses that practitioners should be aware of the total energy delivered to tissues rather than solely focusing on irradiance, as total energy is vital for producing therapeutic effects. He recommends using larger surface area applicators to avoid overheating and to deliver effective doses more evenly across target tissues. Patients should seek devices that not only fit clinical guidelines for dosimetry but are also user-friendly and appropriate for their specific health conditions.
Evaluating Device Safety and Efficacy
When selecting PBM devices, it's essential for users to consider the safety parameters surrounding irradiance levels to prevent thermal injuries. Cronshaw outlines safe irradiance limits, recommending around 500 milliwatts per square centimeter for near-infrared light and 200 milliwatts for red light, with attention to spot size and treatment duration. He notes that while certain high-energy applications have therapeutic benefits, users must remain vigilant about the temperature of treated areas to avoid discomfort and tissue damage. He emphasizes the importance of ongoing research to understand these dynamics better and improve safety standards in PBM practices.
A Holistic Perspective on Light Therapy
This conversation culminates in advocating for a holistic understanding of PBM that acknowledges the intricate interplay between various energy sources, dosimetry, and biological responses. Cronshaw calls for an integration of historical findings with new research trends while urging practitioners to stay adaptable and informed on the evolving landscape of light therapy. He believes that as understanding deepens, clinicians can make better-informed decisions that leverage the full potential of PBM. Ultimately, recognizing the multifaceted effects of light can lead to more effective and widely accepted therapeutic practices.
In this episode, I’m back for the second part of my conversation with Dr. Mark Cronshaw, a highly respected expert in photobiomodulation (PBM), more commonly known as red light therapy.
The same warning applies to this episode as part 1! Again, this conversation is not a simple “how to” practical guide to photobiomodulation. It’s a continuation of going very deep into the scientific, technical, and even theoretical nuances of PBM based on Dr. Cronshaw’s vast research and clinical understanding of the topic.
Be prepared for lots of nerdy PBM science, along with a few practical pearls as our discussion unfolds.
Please listen to part 1 if you haven’t already, and leave any questions you have in the comments on YouTube…we’ll do our best to answer questions in future episodes.
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