I have to agree with james here. You should not be coming on here and saying that your at a plateau at age 19. Your natural Test levels dont even begin dropping until your around the age of 25, which means plateaus shouldn't even be an issue for you right now. You need to fix one if not all of these things before you should even consider a PH. Diet, workout routine, How often do you change up your workout routine. Are you the guy who on a chest day immediately goes to bench press and nothing else? This will affect your results and keep you stuck in a plateau. My knowledge of PHs is still in the learning phase, but I can tell you that even without PH's I never hit plateaus. The reason being is I keep my diet in check. I change up my workout routine constantly. I eat every 2.5 to 3 hrs never exceeding that 3 hr mark (messes up the whole regimen, need to be strict about this). What should your food consist of? Complex carbs with most if not every meal (depending if your leaning or bulking). Lean Protein with EVERY MEAL. Fats should DEFINITELY be in your diet. Are you taking a multivitamin. Are you drinking about a gallon of water a day? Are you taking in fish or flaxseed oil...?Heres a sample of some foods.
Complex Carbs: Brown rice, Ezkiel bread, sweet potatoes, oatmeal, Wheat (not my favorite).
Protein :Chicken Breasts, Lean ground beef, egg Whites (throw a yolk or two in there), Fish (salmon, tilapia, tuna), Isolate protein shakes, Greek yogurts a good one, Turkey breast.
Fats: All natural peanut butter, almonds, peanuts, all natural almond butter, sunflower seeds, avacado, etc....
This is only a couple of foods, plenty more out there you can work from. Any ways Ive been a personal trainer for 4 years and helped out a couple of buddies with all natural body building competitions and competed myself. I know what Im talking about here. If your not following a meal plan like i described then you shouldnt even consider taking a ph. Especially at your age. But if your still going to take the ph regardless of what James and I suggested here, then you should still follow a meal plan like i described above regardless of whether your on a ph or not. Regardless Im throwing this up there to help you out. Hope you take our advice buddy, wish you the best. Good luck
