Photobiomodulation (PBM) by low-level laser therapy (LLLT) and light-emitting diode therapy (LEDT) provides several benefits for muscle tissue as evidenced by in vitro and in vivo studies, and clinical trials. Among these benefits, this chapter covers two recent and very important effects reported in the current literature:
1. the prevention of muscle damage after exercise, including delayed onset muscle soreness; and
2. the improvement of muscle performance (demonstrated by increases in muscle torque, power, or work), workload capacity, fatigue resistance, functional or sport activity, and exercise recovery.
Therefore, this chapter covers the majority of clinical trials that have been published up to February 2016 that aimed at increasing muscle performance and exercise recovery or preventing muscle damage with PBM in healthy volunteers/ athletes. Studies with different purposes were not included.
The use of PBM to prevent muscle damage has primarily been investigated in animal models, irradiating skeletal muscles before a bout of intense exercise (referred to in this chapter as “muscular pre-conditioning”) and by following the muscle damage with measurements of the creatine kinase (CK) levels in the bloodstream. To the best of our knowledge, the first study that used PBM via LLLT to prevent muscle damage was performed by Lopes-Martins et al. in rats. These authors investigated the effects of different doses of a 655-nm laser (0.5 J/cm[sup[2, 1.0 J/cm[sup[2, and 2.5 J/cm[sup[2) to prevent muscle fatigue and muscle damage (CK) induced by neuromuscular electrical stimulation. This study reported a LLLT dose response to decreased CK activity.