Low-level phototherapy to improve exercise capacity and muscle performance: a systematic review and meta-analysis

The aim of this study was to evaluate the effectiveness of pre-exercise low-level phototherapy (Light-Emitting Diode therapy [LEDtherapy] or Light Amplification by Stimulate Emission of Radiation therapy [LASERtherapy]) in increasing exercise capacity and muscle performance of people undergoing exercise when compared to placebo treatment. Randomized controlled trials and crossover studies were sought on CENTRAL, MEDLINE, EMBASE, SciELO, PEDro and LILACS from its inception up to February 2015. References lists of included studies were sought for additional relevant research. Two authors independently extracted data on study design, treatment parameters, exercise capacity (number of repetitions, time to exhaustion, blood lactate concentration and lactate dehydrogenase activity) and muscle performance (torque, power and strength) using an structured table. Agreement should be reached by consensus or by a third reviewer. Sixteen studies involving 297 participants were included. Improvement of number of repetitions (mean difference [MD] [95 % confidence interval] = 3.51 repetitions [0.65–6.37]; P = 0.02), delay in time to exhaustion (MD = 4.01 s [2.10–5.91]; P < 0.0001), reduction in lactate levels (MD = 0.34 mmol/L [0.19–0.48]; P < 0.00001) and increased peak torque (MD = 21.51 Nm [10.01–33.01]; P < 0.00001) were observed when LASERtherapy was applied. LEDtherapy meta-analyses were performed with two studies and retrieved no between-group statistically significant difference in power, lactate levels or time to exhaustion. Although our results suggest that LASERtherapy is effective in improving skeletal muscle exercise capacity, the quality of the current evidence is limited

Electron Transport in the Mitochondrial Respiratory Chain

The metabolic capacity of the eukaryotic cell to convert free energy contained in nutrients into ATP is a process accomplished by a multistep system: the mitochondrial respiratory chain. This chain involves a series of electron-transferring enzymes and redox co-factors, whose biochemical characterization is the collective result of more than 50 years of scientists\u2019 endeavors. The current knowledge describes in detail the structure and function of the individual proton-translocating \u201ccore\u201d complexes of the respiratory chain (Complex I, III, IV). However, a holistic approach to the study of electrons transport from NADdependent substrates to oxygen has recently directed our attention to the existence of specific albeit dynamic interactions between the respiratory complexes. In this context, the respiratory complexes are envisaged to be either in form of highly ordered assemblies (i.e. supercomplexes) or as individual enzymes randomly distributed in the mitochondrial membrane. Either model of organization has functional consequences, which can be discussed in terms of the structural stability of the protein complexes and the kinetic efficiency of inter-complex electron transfer. Available experimental evidence suggests that Complex I and Complex III behave as assembled supercomplexes (ubiquinone channeling) or as individual enzymes (ubiquinone-pool), depending on the lipid environment of the membrane. On the contrary, a strict association of Complexes III and Complex IV is not required for electron transfer via cytochrome c, although there are supercomplexes in bovine heart mitochondria, known as the respirasomes, that also include some molecules of Complex IV. Our recent experimental results demonstrate that the disruption of the supercomplex I1\u2013III2 enhances the propensity of Complex I to generate the superoxide anion; we propose that any primary source of oxidative stress in mitochondria may perpetuate generation of reactive oxygen species by a vicious cycle involving supercomplex dissociation as a major determinant