Background and objective: This study assessed the putative analgesic effect of low intensity, near-infrared laser irradiation (830nm; 1.5 & 9.0J/cm2; continuous wave).
Study design/materials and methods: The current study was completed under double-blind conditions using a standardised form of the submaximal effort tourniquet technique. Healthy naive female volunteers (n = 48) attended on two occasions for pain induction in the non-dominant upper limb, the first during which baseline data were obtained and on a second occasion during which subjects were randomly allocated to either control, placebo, or one of two treatment groups. In the treatment groups, irradiation was applied to ten points on the ipsilateral Erb's point immediately prior to the pain induction procedure at the parameters stated: For the placebo condition, sham "irradiation" was delivered by applying the laser unit without activating the probe. Pain was measured using computerised visual analogue scales and McGill Pain Questionnaires to assess "current pain intensity" and "worst pain experience," respectively.
Results: Whereas analysis of variance and appropriate posthoc tests showed a trend toward hypoalgesia at a radiant exposure of 1.5J/cm2, no significant effects of laser therapy were found.
Conclusions: These results do not provide convincing evidence for the clinical potential of low intensity laser irradiation as a pain relieving modality, at least at the parameters used. Further work is thus necessary to provide objective quantifiable data on the putative clinical efficacy of this modality and the relevance (if any) of irradiation parameters.