Okay - you are about to make the critical mistake that lead all the BBers to the 3 day split and training muscle groups 1x per week. In the late 1980's BBers would routinely train 3 days on and 1 off, some with am/pm sessions. All of a sudden a few guys started to notice that after a layoff they came back stronger and bigger.
In their woeful framework of training theory they believed that you go into the gym, workout to stimulate the muscles, recover and adapt to a bigger/stronger state, and then go back in and reapply. The idea is that you time your workouts and catch this supercompensation wave just as you recover but before the muscles attrophy. HIT training is probably the ultimate logical application of this as they seek to make minimal inroads, get the adaptation, and then return. You'll find your frequency gets less and less.
This is called single factor theory or simply supercompensation and it sounds really great and logical right? This is why BBing programs changed so drastically with regard to frequency and had impacts into training to failure also (which is flawed on a consistent basis).
Anyway, this is fucking wrong. The body doesn't work like that. I mean, it sounds good and it would be cool if it did, but you have this really sleek and simple model that doesn't hold up and there's a boatload of evidence behind this and outside of BBing, in the world of Pro, Div1, or Olympic level athletics you won't see this single factor type of program applied. The terms periodization and dual factor theory apply here.
I'm not going to type much more to explain it but here are some explanations and then below, I'll just continue and expect that you've read at least the first one. The 2nd link is part 1 of an article at Core magazine and if you like it just poke around for part 2 which lays out the program - or just PM me and I'll send you links.
Dual Factor Theory - Why this Works:
(The further one progresses the more critical it becomes to understand basic training concepts like this. If you aren't familiar with this, it is absolutely essential. This is how top athletes in sport are trained the world over and this includes adding LBM in addition to strength, speed, and power.)
JS182:
http://forum.mesomorphosis.com/showpost.php?p=48&postcount=3
Matt Reynolds:
http://www.readthecore.com/200501/reynolds-dual-factor-training.htm
Madcow (post #15 and on):
http://www.elitefitness.com/forum/showthread.php?t=372686
So anyway, what you have basically done is gone from a higher volume/higher frequency period to a period lower in each. This is akin to loading/deloading periods. What you are noticing is the rebound/delayed compensation effect. This doesn't carry on forever because you won't be stimulating much progress on a 1x per week program to rebound or compensate from. It's interesting to note that the idea behind periodization is that the body can tolerate much higher loads over a short term as compared to an infinite term (i.e. non-periodized). This is used advantageously by loading the athelte for a period and then deloading and allowing for adaptation to take place. It's a delayed compensation. As stated in the links - this is nothing new, this is standard training theory, everyone in the world is seemingly aware of this with the exception of BBers. Go to the Olympic Training center and see how we train our sprinters, throwers, Oly lifters etc... Now go to China, Britain, Bulgaria, South Africa, everywhere - it's just totally common accross the world.
So anyway - if you only want to train 1x that's your business. But you are basically where BBing was in the early 1990s (there were other major problems too like using all machines, no planned weight progression, etc...) and I'd prefer not to see you jump off the same cliff out of ignorance that all of them did.
Here's another sample dual factor/periodized program:
http://www.elitefitness.com/forum/showpost.php?p=4764723&postcount=381
Here's the table of contents in the master thread where all of this stuff came from:
http://www.elitefitness.com/forum/showthread.php?t=375215