I had trouble building definition and muscle mass with just protein, but as soon as I started using this product, I had a energy boost, strength, and more stamina immediately and within the first week I was adding muscle! Nothing I used in the previous 10 years comes close to the results I am experiencing now! A must try for anyone wanting to add definition, strength and more muscle. Product was cheaper than other sites, with delivery a day early. This is a go to company and product.