Immediate effect of photobiomodulation therapy on Achilles tendon morphology and mechanical properties: An exploratory study

Objectives: Evaluate the immediate (within 4 hours) effects of laser-induced photobiomodulation (PBM) therapy on Achilles tendon morphology and mechanical properties in healthy and pathologic tendons. Materials and methods: Twenty people with healthy Achilles tendons and twelve people with Achilles tendinopathy participated. One Achilles tendon received PBM treatment following an established protocol, and the contralateral side received a placebo treatment. Achilles tendon morphology and mechanical properties were evaluated bilaterally with ultrasound imaging and continuous shear wave elastography immediately before treatment, immediately after treatment, then 2 and 4 hours after treatment. Results: There were no immediate effects of PBM on tendon morphology or mechanical properties when comparing the PBM-treated side and placebo-treated side within each cohort. Additionally, the effects of PBM did not differ between healthy and pathologic Achilles tendons. Conclusion: When treated with a laser-induced PBM treatment, healthy and pathologic Achilles tendons do not have immediate (within 4 hours) changes in tendon morphology or mechanical properties. These findings suggest that PBM therapy can be administered before other clinical treatments or high-load activities.