19... terrible decision. Was nowhere near my genetic max yet, i was just young and impatient. Yes I gained 30lbs of muscle that year but I could have gained that naturally. My best gains have actually been recent, in my mid-to-late 30's, and they show no signs of slowing down. I will not reach my peak till my 40's I think.. so I wish I would have waited till 25 or so at least!