Immediate Effect of Photobiomodulation using 180 mW, 810 nm Laser with Continuous Irradiation on Pressure Pain Threshold and Temporal Summation of Pain: A Single-blind, Cross-over Study in Healthy Volunteers

This crossover study used a 180 mW laser to assess the immediate effects of photobiomodulation (PBM) on the pressure pain threshold (PPT) and temporal summation of pain (TSP) in ten healthy volunteers. The participants were randomly assigned to either sequence AB (n = 5) or BA (n = 5). The laser group (Intervention A) underwent PBM therapy. The parameters included a power output of 180 mW, a wavelength of 810 nm, a beam area of 0.35 mm2, a power density of 510 mW/mm2, an energy of 54 J, and an energy density of 150 J/mm2. In contrast, the control group (Intervention B) received sham laser irradiation. The primary outcome measures were the PPT and TSP pre- and post-irradiation, with the TSP magnitude (TSPm) calculated and utilized for analysis. The baseline PPT and TSPm values showed no significant differences between the groups. In the laser group, the PPT significantly increased post-irradiation compared to pre-irradiation (p < 0.001, r = 0.89). The control group exhibited no significant changes pre- and post-irradiation (p = 0.864, r = 0.06). In the laser group, the TSPm decreased significantly post-irradiation compared to pre-irradiation (p = 0.037, r = 0.63). In the control group, no significant differences were observed pre- and post-irradiation (p = 0.399, r = 0.28). These findings suggest that PBM with 180 mW laser may increase PPT and inhibits TSP.