The Effect of Photobiomodulation on Microvascular Blood Flow: The Role of Wavelength and Skin Temperature

This is a within-subject experimental study in which each participant completes two study sessions. Microvascular and systemic variables are continuously monitored in response to photobiomodulation delivered at either a blue or near-infrared wavelength, with each wavelength applied in a separate session.

Each session includes a baseline period with controlled breathing, followed by photobiomodulation and a 20-minute post-intervention follow-up period. Peripheral microcirculatory responses are assessed using noninvasive thermography, photoplethysmography, and laser Doppler flowmetry.

Inclusion criteria

• Healthy males and females, between 20 and 75 years of age.
• Willing to sign informed consent.
• Willing to participate in two separate sessions, one for each wavelength.
• Able to avoid caffeine and alcohol for at least 3 hours before each session.
• Able to sit comfortably with both hands at heart level for the full measurement duration.

Exclusion criteria

• Currently smoking
• Any abnormal skin condition in the area of light irradiation.
• Pregnant, having given birth less than 3 months ago, and/or breastfeeding.
• History of photosensitive conditions or use of photosensitizing medications
• Suffering from significant concurrent illness, such as cardiac disorders or pertinent neurological disorders.
• As per the Investigator's discretion, any physical or mental condition that might make it unsafe for the subject to participate in this study.