A) Mitochondria of myotubes from C2C12 cells without low-level laser therapy (LLLT) or light-emitting diode therapy (LEDT). There is a normal flux of electrons (red arrow) through all complexes of electron transport chain, normal pumping of H+, normal synthesis of ATP and modest take up of TMRM by the mitochondrial matrix. B) Mitochondria of myotubes from C2C12 cells 3 to 6 hours after LEDT. There is an increased flux of electrons (ticker red arrow), increased pumping of H+, increased synthesis of ATP and increased take up of TMRM by the mitochondrial matrix. Abbreviations: I, II, III, IV and V= complexes of the mitochondrial electron transport chain; H+= proton of hydrogen; - = electron of hydrogen; O2= oxygen; H2O= metabolic water; Q= quinone; COX= cytochrome c oxidase; ATP= adenosine triphosphate;TMRM= tetramethyl rhodamine methyl ester.