Effect of low-level laser therapy (GaAlAs - λ660 nm) on muscle function

Introduction:Low-level laser therapy (LLLT) is effective in preventing fatigue and in stimulating the microcirculation and cellular activity. In this study, we examined the effect of LLLT on injured tibial muscle in vivo by assessing muscle function during fatigue.MethodsTwenty-four male mice were used. Each mouse received an injection of sterile 0.9% saline solution (50 µL) in the right tibialis anterior muscle, after which the tendon of the muscle was exposed, connected to an isometric transducer and subjected to a resting tension of 1 g. A bipolar electrode was attached to the tibial nerve for electrical stimulation. The mice were randomly allocated to one of two groups: G1 (control: 3 h – n=8 and 9 h – n=5) and G2 (treated with GaAlAs laser, λ660 nm, 35 mW, 0.6 J, 17 s: 3 h – n=6 and 9 h – n=5).ResultsIn G1 mice, the amplitude of the tetanic contracture in response to induced fatigue remained unchanged during six consecutive tetani. The amplitude of the tetanic contractions in response to electrical stimulation (4-8 mV) was also unchanged. These results indicated muscle intactness in response to the load imposed by tetanus. In G2 mice, there was an increase in the amplitude of contraction after 3 h and 9 h when compared to G1 at 83% tetanus.ConclusionThese results indicate that exposure of muscle to LLLT enhanced the contractile force and increased the resistance to muscle fatigue without causing morphological damage to cellular structures.

引言：低强度激光疗法（Low-level laser therapy, LLLT）可有效预防肌肉疲劳，并刺激微循环与细胞活性。本研究通过评估疲劳状态下的肌肉功能，在体环境中探究了低强度激光疗法对受损胫骨肌的干预效果。
方法：本实验共纳入24只雄性小鼠。每只小鼠的右侧胫骨前肌均注射50 μL无菌0.9%生理盐水，随后暴露该肌肉的肌腱，将其连接至等长换能器，并施加1 g的静息张力。将双极电极附着于胫神经以实施电刺激。将小鼠随机分为两组：G1组（对照组：3小时亚组n=8，9小时亚组n=5）与G2组（GaAlAs激光照射组，波长660 nm，功率35 mW，照射能量0.6 J，照射时长17 s：3小时亚组n=6，9小时亚组n=5）。
结果：G1组小鼠在连续6次强直收缩诱导疲劳后，强直挛缩的振幅未发生显著变化；电刺激（4~8 mV）诱导的强直收缩振幅同样保持稳定。上述结果表明，肌肉在强直收缩施加的负荷下保持结构完整。而G2组小鼠在强直收缩强度达到83%时，其收缩振幅相较于G1组在3小时与9小时时间点均有所提升。
结论：本研究结果显示，对受损肌肉施加低强度激光照射可增强其收缩力量，并提升肌肉对抗疲劳的能力，且不会对细胞结构造成形态学损伤。