['The effects of LLLT were studied during muscle regeneration through gene expression.', 'It was evaluated 10 and 50J/cm(2) doses during 7, 14 and 21days post cryoinjury, through histopathological analysis and mRNA MyoD, Myogenin, Vegf and Cox-2 expression.', 'Irradiated groups presented less inflammatory process than control group after 14 and 21days. Cox-2 levels were downregulated in all irradiated groups after 7, 14 and 21days. On day 7, both treated groups had a downregulation of Vegf levels, and an upregulation after 14 and 21days, mainly with 50J/cm(2). The MyoD levels were upregulated with high dose in all periods and with low dose after 21days. Myogenin expression was downregulated in both treated groups after 7days, and was upregulated with 10J/cm(2) after 21days.'] Does low-level laser therapy ( LLLT ) ( 660nm ) alter gene expression during muscle healing in rats?