These days HGH is the buzz word with supplement companies as it increases muscle mass, keeps women looking and feeling young, hell who knows, it's probably freaking cures cancer too or so some company will say. Anyway I'm not bashing on HGH as it's a natural thing in the body and very good, just that too many supplement companies claim their products increase it and generally it's a bunch of BS. Essentially Argenine increase blood flow throughout the body especially in the muscles. It's long been used as a supplement to help men get a hard on cause it increases blood flow to the muscles and the male member is a muslce and increased blood flow is what causes it to get hard. So enough with that graphic imagery. Anyway in increasing blood flow to the muscles it increases the amount of nutrients into the muscles since blood carries nutrients throughout the body. It also increases the "pump" in the muscles as some people have reported incredible pumps while some have even reported it pumps up the muscles so much it's painful and they can't finish there workouts although this is rare. There are no known side effects I know of although it is suggested you not take it if you are taking any form of nitrates, prego, suffer from migrane headaches or are at a high risk or have had a stroke. One concern I have regarding Argenine is how it affects the heart and blood pressure since it's increasing blood flow so much. I've not heard any thing good or bad regarding this but it might be something you would want to think about.