INTRODUCTIONThe lipid messenger phosphatidic acid (PA) plays a critical role in the stimulation of mTOR signaling. However, the mechanism by which PA stimulates mTOR is currently unknown. Therefore, the purpose of this study was to compare the effects of various PA precursors and phospholipids on their ability to stimulate mTOR signaling and its ability to augment resistance training-induced changes in body composition and performance.METHODSIn phase one, C2C12 myoblasts cells were stimulated with different phospholipids and phospholipid precursors derived from soy and egg sources. The ratio of phosphorylated p70 (P-p70-389) to total p70 was then used as readout for mTOR signaling. In phase two, resistance trained subjects (n = 28, 21 ± 3 years, 77 ± 4 kg, 176 ± 9 cm) consumed either 750 mg PA daily or placebo and each took part in an 8 week periodized resistance training program.RESULTSIn phase one, soy-phosphatidylserine, soy-Lyso-PA, egg-PA, and soy-PA stimulated mTOR signaling, and the effects of soy-PA (+636%) were significantly greater than egg-PA (+221%). In phase two, PA significantly increased lean body mass (+2.4 kg), cross sectional area (+1.0 cm), and leg press strength (+51.9 kg) over placebo.CONCLUSIONPA significantly activates mTOR and significantly improved responses in skeletal muscle hypertrophy, lean body mass, and maximal strength to resistance exercise.