I am 42 years old and just completed a 6 week cycle of Doug Crist's workout program. It consists of using 50-60% of 1rep max, doing alternating sets(4 at once) of 12-15 til you get 12 sets for each exercise. For example, 4 sets of incline press, 4 sets of front pulldowns, back to incline press for 4 sets, etc til you complete 12 sets of 12-15 reps each set.
The workout itself is not taxing, metabolically speaking, but after a month of this people were commenting how much bigger and "buff" I look. I lost 2 lbs on the scale!! I was very surprised by this. I expected to have gained 4-5 lbs by how my clothes felt, others comments, and the mirror. My shirts were definitely tighter and that pumped feeling didn't leave even on off days.
My leg mass, in my opinion, didn't increase but my jeans fit better. The most noticeable improvement were my chest and arms. The weights I used were pathetic to most but it caused something to change. so much for having to gain weight to get bigger.
Its been a couple weeks since I changed programs. Currently, I am doing xreps(Steve Holman) with much lower sets and higher intensity and just don't like it as much. With Crist's program, I had more energy and felt better and again I think I looked better. I am all about appearance and don't care one bit how strong am. Here's my stats if interested: Age 42, Ht, 6 0, Wt-190 lbs, bodyfat 8%.