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

Abstract

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. Methods: Twenty-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). Results: In 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. Conclusion: These 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.

Low-intensity laser therapy improves tetanic contractions in mouse anterior tibialis muscle injected with Bothrops jararaca snake venom

“…Lopes-Martins et al (2006) found that GaAlAs laser at λ 630-680 nm protected against muscle damage, with a concomitant decrease in creatine kinase release, stimulated the release of cGMP to cause local vasodilatation and helped to maintain muscle contractile strength in rats. More recently, Giaretta et al (2015) observed that LLLT improved muscle function in mice, as assessed by the enhanced tetanic response and resistance to fatigue.…”

“…This conclusion is supported by the findings of Leal et al (2009), who reported that phototherapy (infrared radiation) attenuated the skeletal muscle fatigue in biceps muscles of professional male volleyball players. The possible cellular mechanisms involved in this enhanced resistance to fatigue have been investigated in recent studies (Giaretta et al, 2015;Kelencz et al, 2010;Maciel et al, 2013;Muñoz et al, 2013;Reis et al, 2015). Passarella and Karu (2014) reported that mitochondria respond to low intensity light and that this response increases ATP production and facilitates cell multiplication.…”

“…For the experiments, the right anterior tibialis muscle was used, as described by Giaretta et al (2015). Mice were injected with B. jararaca venom (40 µg in 50 µl of 0.9% saline); this dose of venom was chosen based on previous publications by our group Dourado et al, 2011).…”