OBJECTIVES: Kamishimotsuto (KST) is a supplement containing 13 different herbs including Phellodendron bark, Anemarrhena rhizome and ginseng that have been shown to activate mammalian target of rapamycin complex 1 (mTORC1) and thereby increase muscle protein synthesis in vitro. However, the combined effect of KST and resistance exercise on muscle protein anabolism has not been investigated in vivo. Therefore, the purpose of this study was to investigate the effect of KST supplementation, resistance exercise on (mTORC1) signaling and subsequent muscle protein synthesis. METHODS: Male Sprague-Dawley rats were divided into two groups: one group received KST (500 mg/kg/d in water) and the other group received placebo (PLA) for 7 d. After 12 h of fasting, the right gastrocnemius muscle was isometrically exercised via percutaneous electrical stimulation. Muscle samples were analyzed for muscle protein synthesis (MPS) and by western blotting analysis to assess the phosphorylation of p70S6K (Thr389), rpS6 (Ser240/244), and Akt (Ser473 and Thr308). RESULTS: KST supplementation for 7 d significantly increased basal p-Akt (Ser473) levels compared with PLA, phosphorylation of the signaling proteins and MPS at baseline were otherwise unaffected. p-p70S6K and p-rpS6 levels significantly increased 1 h and 3 h after exercise in the PLA group, and these elevations were augmented in the KST group (P < 0.05). Furthermore, MPS at 6 h after resistance exercise was greater in the KST group than in the PLA group (P < 0.05). CONCLUSIONS: While resistance exercise alone was able to increase p70S6K and rpS6 phosphorylation, Kamishimotsuto supplementation further augmented resistance exercise-induced muscle protein synthesis through mTORC1 signaling.