Low-level laser (light) therapy (LLLT) on muscle tissue: performance, fatigue and repair benefited by the power of light

Abstract

The use of low level laser (light) therapy (LLLT) has recently expanded to cover areas of medicine that were not previously thought of as the usual applications such as wound healing and inflammatory orthopedic conditions. One of these novel application areas is LLLT for muscle fatigue and muscle injury. Since it is becoming agreed that mitochondria are the principal photoacceptors present inside cells, and it is known that muscle cells are exceptionally rich in mitochondria, this suggests that LLLT should be highly beneficial in muscle injuries. The ability of LLLT to stimulate stem cells and progenitor cells means that muscle satellite cells may respond well to LLLT and help muscle repair. Furthermore the ability of LLLT to reduce inflammation and lessen oxidative stress is also beneficial in cases of muscle fatigue and injury. This review covers the literature relating to LLLT and muscles in both preclinical animal experiments and human clinical studies. Athletes, people with injured muscles, and patients with Duchenne muscular dystrophy may all benefit.

Keywords: ATP; low level laser therapy; mitochondria; muscle fatigue; muscle injury; reactive oxygen species; satellite cells.

Figures

Figure 1

Number of LLLT or LEDT radiation points applied on femoral quadriceps muscle based on references [36] (A), [31] (B), [32] (C) and [33] (D).

Figure 2

Based on reference [32]: (A) LLLT radiation points on femoral quadriceps muscle. (B) Mitochondrial creatine shuttle mechanism. (C) Lactate oxidation by mitochondrial pathway.

Figure 3

Based on reference [51]: Deprotonation of histidine and formation of the N-Zn bond to restore the active center structure and activity of the superoxide dismutase enzyme (SOD) by LLLT or LEDT.

Figure 4

Based on reference [1]. Effects of LLLT or LEDT on reactive oxygen species (ROS) and reactive nitric species (RNS) production and antioxidant enzymes. ⊗: decreased or inhibited production.

Figure 5

Based on references [1, 32, 40, 49]. Effects of LLLT or LEDT on reactive oxygen species (ROS), reactive nitric species (RNS), mitochondria and muscle contraction. SERCA = sarcoplasmatic reticulum Ca2+ pump. Dashed line: inhibited activity and ⊗: decreased or inhibited function.

Figure 6

Based on references [10, 11, 84]. Mitochondrial biogenesis, protein synthesis and protein breakdown signaling modulated by LLLT associated to exercise. Gray boxes were upregulated by LLLT and black boxes were downregulated by LLLT.