Increasing and maintaining skeletal muscle mass known to have beneficial effects to maintain stability of body's metabolism in young adult, while reduction of skeletal muscle strength and mass associated with physical disability and increased morbidity and mortality. Skeletal muscle growth involves activation of satellite cells. This study investigated the effect of Nutmeg seed extract free safrole and myristicin (Nutmeg) on skeletal muscle mass and activation of satellite cells in soleus and gastrocnemius muscle. Ten male Wistar strain rats ages 6 week were divided into 2 groups randomly. Nutmeg extract were given to treatment group for 12 weeks. By the end of treatment period, soleus and gastrocnemius muscle were isolated and subjected for gene expression analysis. Nutmeg administration increased gastrocnemius muscle mass (p=0.025) and soleus muscle mass (p=0.028). In soleus muscle, Nutmeg significantly increase Akt (p=0.007) and MyoD gene expression (p=0.037) but not the Myf5 gene expression (p=0,221). While gastrocnemius muscle of the Nutmeg group showed higher expression on Akt gene (0.038). However, no difference were observed in gastrocnemius Myo D (p=0,081) and Myf5(p=0,323) mRNA expression. It suggest, that Nutmeg extract increase MyoD expression through activation Akt pathway mainly in Soleus muscle. As the conclusion, Nutmeg extract administration increase protein synthesis in skeletal muscle through satellite cell activation partly via Akt and MyoD gene expression. Keywords: Skeletal muscle, Nutmeg, autophagy, satellite cells.