Single Application of Low-Level or Infrared Laser Therapy Not Effective in the Short Term for Neck Pain: A Randomized Controlled Clinical Trial.

OBJECTIVE

This study aimed to compare short-term effects of low-level laser therapy and far-infrared radiation on pain intensity, pressure-induced pain, and skin temperature of the trapezius muscle of individuals with subacute and chronic neck pain.

METHODS

A randomized, sham-controlled, superiority clinical trial with 3 parallel arms and blind evaluator was performed. Ninety-one individuals were treated with phototherapy for subacute and chronic neck pain. Pain intensity was assessed using visual analog scale. Pressure-induced pain was assessed using a pressure dynamometer. Skin temperature of the trapezius region was evaluated with infrared thermography. Individuals were evaluated before (T0), immediately after (T1), 10 minutes (T2), 20 minutes (T3), and 48 hours (T4) after 1 session of phototherapy. Individuals were randomly allocated into 3 groups: (1) laser therapy (GLAS), punctual laser application (808 nm, 0.5 J/cm², power of 10 mW); (2) infrared (GINF), application at 30 cm and incidence angle of 90° for 30 minutes; (3) sham (GSHAM), simulated punctual laser. Mixed linear models were performed using group, time, and group-versus-time interaction, considering a first-order automatic covariance matrix.

RESULTS

Pain intensity reduced in intragroup analysis among all evaluation times (P < .05), but not intergroup. Pressure-induced pain was not altered. There was increased skin temperature with infrared at T1 and T2 compared with laser therapy and sham (P < .05).

CONCLUSIONS

A single application of low-level or infrared laser therapy was not effective in the short term for subacute and chronic neck pain and did not change skin temperature in trapezius region.