If you're goal is to be a pro bodybuilder, it is true you won't be doing things like the every day gear user. There's undoubtedly a lot more risk involved and generally the same rules do not apply. That doesn't mean you should do it, it just means you should recognize the risk.
As for age, I remember reading a few years ago back when Tony Freeman turned pro, the average age of a bodybuilder earning his pro card was 32. Sure, younger guys do earn pro cards, Heath being a good example, but the days of most being in their early to mid-20's is long, long gone. There are very few that turn pro with only a few years of bodybuilding training and gear use under their belt. Again, Heath being a current notable exception. Most have been doing what they do for a decade or more.
Amateurs with the goal of turning pro...when you see a guy turn pro, you'll notice the really good ones don't get massively huge until after they turn pro. They'll use a large amount of gear to turn pro, but it often increases exponentially once they turn pro.
For the off-season amateur, Tren isn't always needed, but butt loads is when it's contest time. The exception can be during the off-season some will use it to help with plateaus. Large amounts of Test and Deca are common with butt loads of HGH. If Tren is used, it's not uncommon for there to be a rotation between Deca and Tren. Just an example:
WK 1-8 Nandrolone/Test
WK 7-15 Tren/Test
WK 14-20 Nandrolone/Test
...and so on and so on.
And I'm not saying this is all that's used by any means. IGF-1 is very common. But this is just a good example of possible off-season Tren/Nandro use. Dbol in 4-6wk rotations is also common.
Anyway, just some thoughts and observations. Take it or leave it
