The main reason I thought I couldn't continue to improve my physique over 45 is the physiques you normally see of bodybuilders in the masters/old timers classes at bodybuilding shows never seem as defined or tight as younger guys. That's why when I see a physique like yours and guys like Eric Orrao (who is amazing at 48 - check out his web site) I am really inspired.
I've also always read about muscle wastage over 45 and the difficulty in avoiding the muscle flabbiness that comes with old age. Like you I think boosting testosterone is the key and since I turned 40 I have been regularly taking Tribulus while raising my work-out intensities and increasing my protein intake (desperation can be a wonderful thing can't it ? ha ha).
Testo boosters are okay, I am not personally clear on if they work, as only before-and-after measurements of testosterone levels in the blood would prove that.
But testo boosters are not at all like taking the real thing, such as Androgel, which is a topical treatment, or better for bodybuilders, Testosterone Ciprionate injections.
Both men and women lose vital hormones as they age, and the resistance in society at replacing them is very, very odd, since people do all kinds of damaging things to themselves continually, like smoking and drinking, yet are told that hormone replacement is somehow "unsavory", when in fact the benefits are nothing short of wondrous. The reason we feel young again is because we have the hormones back that we once had.
Over-training is a reality, since your muscle needs a full week or more to recoup and rebuild. Without the rest, you are tearing it down again before it had a chance to reach it's full growth from the last workout, and thus it never gets the chance to fully blossom.
LOTS of guys are resistant to this idea, and over-train regardless, just as they fail to correct poor workout technique, or fail to rehab injuries and try to "work through" the pain. All the above are counter productive.
One of the many absurdities in popular belief is the vilification of steroids. None of the so-called adverse side effects can happen to someone taking recommended dosages...all the horror stories are fabricated —when is the last time you heard about anyone dying from steroids, or ending up in the ER? We are inundated by unsafe drugs at every turn, but instead of focusing on deaths and injury from all of those, the media loves to focus on steroids.
It's a safe hot-button issue, as no one defends steroids. But if your doc is willing, a therapeutic dose (as opposed to the illegal mega-doses that some bodybuilders abuse) would definitely harden you up, and have many other benefits, including well-being overall.
I cannot take steroids for the same reason I can't take testo, but steroids are a miracle pharmaceutical that have saved millions of lives, including hundreds of thousands of AIDS patients who would have never lived long enough to see the dawn of the drugs that have made AIDS a manageable disease.
My partner Alex in the video with me is a physician and an AIDS specialist, and also has a thriving bodybuilder clientele, because he is one himself. So my info and experience comes from 7 years with him.
Work out intensely, then REST. I hope you are working just one body part per session...that way it has a week to recoup before you work it again.