Being in my my mid 40's and on no anabolics, I have come up with a system that gives enough intensity to progress but avoids the overproduction of cortisol which I've found lowers my testosterone levels. I train in 3 week cycles. Week 1 is heavy, high intensity about 3 sets per exercise and 3 to 4 exercises per bodypart. Week 2 is the most intense of the cycle and borders on overtraining: 4 sets heavy per exercise with some drop sets and other intensity amplifying techniques..around 16 sets per bodypart. Week 3 brings down the intensity level but ups the rep range to 15 to 20, maintaining the muscle but not overly stressing the adrenals. I've found after several high intensity weeks in a row, my libido starts to decline signifying a drop in test levels. By only doing 2 weeks consecutive high intensity followed by a 3rd week of lighter training, my test levels stay high. After 3 or 4 months of this I take a full week off. This keeps my joints from being overly inflamed as well. Seems to be working well.