Effect of low-power gallium-aluminum-arsenium noncoherent light (640 nm) on muscle activity: a clinical study

Photomed Laser Surg. 2010 Oct;28(5):647-52. doi: 10.1089/pho.2008.2467.


Background data: Studies have shown the significant effects of electromagnetic irradiation in the visible region, with laser as an irradiation source. However, the effect of LEDs (light-emitting diodes) irradiation in similar wavelengths is not known.

Objective: The purpose of this clinical study was to verify the effects of the LED (640 nm with 40 nm full bandwidth at half maximum) on muscle activity.

Methods: The study was done with 30 test subjects, of both genders, aged 23 ± 3 years, with a mean weight of 60 kg, divided into three groups (n = 10). Fatigue was induced through the maximum power of a bite, for 60 s in two overlaid occlusal platforms, coupled to a load cell and to a biologic signal-acquisition device. LED irradiation of the right masseter muscle was applied to all subjects. The left muscle received placebo treatment. Irradiation was applied in eight points on the right masseter muscle (transcutaneous), 1.044 J per point, 2.088 J per point, or 3.132 J per point, 0.116 W, 0.522 cm(2) spot size, 0.816 cm spot Ø, continuous wave, perpendicular to the skin.

Results: An increase in muscle activity was observed after irradiation with 1.044 J per point (p < 0.05). A significant increase (p < 0.01) in the time before fatigue was observed in the irradiated muscle with 2.088 J per point, without a change in the force of contraction (p > 0.05). This change was not observed with 1.044 J per point and 3.132 J per point. The results suggest a dose-dependent relation with this kind of noncoherent irradiation in the red region of the electromagnetic spectrum in the muscle-fatigue process.

Conclusion: It was concluded that LED can be used as a clinical tool to increase muscle activity (1.044 J per point) and to prevent fatigue (2.088 J per point), without change in the muscle force.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Electromyography
  • Female
  • Humans
  • Lasers, Semiconductor / therapeutic use*
  • Low-Level Light Therapy / methods*
  • Male
  • Masseter Muscle / physiology
  • Masseter Muscle / radiation effects*
  • Muscle Contraction / physiology*
  • Muscle Contraction / radiation effects
  • Muscle Fatigue / physiology
  • Muscle Fatigue / radiation effects*
  • Radiation Dosage
  • Reference Values
  • Sampling Studies
  • Sensitivity and Specificity
  • Statistics, Nonparametric
  • Young Adult