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Background and Objective: Myocytes apoptosis has been considered as a major cause of sarcopenia.The aim of this study was to biochemically analyze the effects of low level laser irradiations(LLLI) associated with medium intensity endurance exercise on BAX, bcl-2 and insulin-like growth factor(IGF)-1 protein and sirtuin1(SIRT1)/peroxisome proliferator-activated receptor-y coactivator-1α(PGC-1 α) axis gene mRNA expression to preventing sarcopenia in aged Study Design/Materials and Methods: Forty female Wistar rats(18 months old) were randomly divided into four groups(n=10 per group):control-sedentary(C), medium intensity endurance exercise(E), LLLI-sedentary(L), and LLLI plus E(LE).Trained rats performed a 8-week on treadmill running(15 km/h,5 days per week, 15 min per day).Depending on the group protocol, the LLLI device (810 nm, 200 mW/cm2, spot size 0.5 cm2) was used for 30s either as the only method or after the exercise training had been performed.Bax, bcl-2, IGF-1 protein expression and mRNA of SIRT1/PGC-1α axis gene was determined by western blot and reverse transcriptase polymerase chain reaction(RT-PCR) at 24 h after exercise or LLLI, respectively.Results: Significant increases were noted for the gastrocnemius muscle weights(P＜0.05), the muscle relative weights(P＜0.01), the bcl-2/BAX ratio(P＜0.05) and SIRT1, PGC-1 α, mitochondrial transcription factor A(TFAM), superoxide dismutase(SOD)-2, bcl2/adenovirus E1B 19kD-interacting protein 3(BNIP3) mRNA level(P＜0.05) of the L group, the E group, and the LE group compared to the C group.The bcl-2 and IGF-1 protein expression for the LE group were significantly higher than for the C group(P＜0.01).The BAX protein expression and the caspase-3 mRNA level for the L group and the LE group were significantly lower than for the C group(P＜0.05).The PGC-1α mRNA level for the E group and LE group were significantly higher than the L group(P＜0.05), respectively.It was interesting that significant increase were found in IGF-1 protein level, bcl-2/BAX ratio, mRNA of SIRT1 and SOD-2 for the LE group(P＜0.05) compared to the E group and the L group, respectively.Conclusions: These findings suggest that both the endurance exercise and the LLLI can inhibit mitochondria-driven myocytes apoptosis by stimulating SIRT1/PGC-1 α axis mRNA expression, thereby increasing the muscle weight of aged rats.Despite the increased muscle weight being similar for all treated groups we can report that IGF-1/SIRT1/SOD-2 signaling pathway mediated the photobiomodulation further optimized effect of medium intensity endurance training protecting against sarcopenia by inhibiting myocytes apoptosis in aged rats.