Análise dos padrões dose-resposta de diferentes comprimentos de onda da laserterapia de baixa potência na fadiga muscular em ratos

Abstract

Aim: To evaluate effects of low-level laser therapy (LLLT) immediately before titanic contractions in skeletal muscle fatigue development and possible tissue damage. Methods: Male Wistar rats were divided into two control groups and nine active LLLT groups receiving one of three different laser doses (1, 3 and 10 J) with three different wavelengths (660, 830 and 905) before 6 tetanic contractions induced by electric stimulation. Skeletal muscle fatigue development was defined by the percentage (%) of the initial force each contraction and tima until 50% decay of initial force, while total work was calculated for all sixth contraction. Results: Several LLLT doses showed some positive effects on peak force and time to decay for one or more contractions, but in terms of total work, only 3 J/660nm and 1 J/905nm wavelengths prevented significantly (p<0,05) the development of skeletal muscle fatigue. All doses with wavelengths of 905nm, but only the dose of 1 J with 660nm wavelength decreased CK activity (p<0,05). Qualitative assessment of morphology revealed lesser tissue damage in most LLLT-treated groups, with doses of 1 3 J/660nm, and 1, 3 and 10J/905nm providing best results. Conclusion: Optimal doses of LLLT significantly delayed the development skeletal muscle performance and protected skeletal muscle tissue againstdamage. Our findings also demonstrate that optimal doses are partly wavelength-specific, and consequently must be differentiated to obtain optimal effects on development of skeletal muscle fatigue and tissue preservation.