title: Effects of 808 nm low-power laser irradiation on the muscle contraction of frog gastrocnemius.
abstract: OBJECTIVE
  The efficacy of low-power laser irradiation (LLI) on muscle fibers remains unclear; therefore, we examined the effect of LLI (808 nm: 60 or 100 mW) on muscle contraction and conducted waveform analyses of the twitch curve, including alterations in the peak amplitudes of tension (AMP), latency (LAT), contraction period (CP), and relaxation period (RP).
  
  
  METHODS
  The sciatic nerve-gastrocnemius muscles of 35 frogs (Xenopus laevis) were prepared. In Experiment 1, continuous stimulation for gastrocnemius contraction was delivered to the sciatic nerve (10 minutes); the experimental group simultaneously received LLI. In Experiment 2, two sets of stimulation and cessation (2 minutes each) were repeated after the initial stimulation period (2 minutes); the experimental group received LLI during the resting period.
  
  
  CONCLUSIONS
  In Experiment 1, 60 mW LLI significantly facilitated an attenuation of AMP and maintained a smaller prolongation of CP (P<0.05), whereas 100 mW LLI significantly influenced a retardation of AMP attenuation and LAT prolongation (P<0.05). In Experiment 2, 100 mW LLI significantly influenced AMP attenuation and LAT prolongation by retardation (P<0.05); almost no effects were obtained in the case of 60 mW LLI. These results suggest that 808 nm LLI influences both synaptic signal transmission at the neuromuscular junction and excitation-contraction coupling in the muscle fibers, but not the relaxation process. We conclude that LLI at relatively high doses can influence muscle by retarding AMP attenuation and LAT prolongation.
authors.affiliation: Department of Information Systems Science, Graduate School of Engineering, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577, Japan.
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Komatsu
authors.forename: Tomihiro
authors.initials: T
authors.lastname: Kubo
authors.forename: Shinichi
authors.initials: S
authors.lastname: Kogure
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Matsuda
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Watanabe
mesh_terms: D000818:Animals; D007834:Lasers; D009119:Muscle Contraction / Q000528:radiation effects*; D018482:Muscle, Skeletal / Q000502:physiology* / Q000528:radiation effects*; D014982:Xenopus laevis