There is a lot of good info here but if anyone is interested I still have a lot of questions:
1. Tote mentioned that as weight goes up volume (in general should go down), do we know of any numeric relations? If I am at 75% of my 5rm it seems I should do less volume than 75% of my 15rm, is this a sliding scale?
Unfortunately, we still don't know enough in this area to be really sure of anything. At this point, I would recommend starting around 25-30 total reps in the earlier part of the cycle and by the heavier part of the 5s, be shooting for 15-20 total reps for each muscle group. Keep in mind that I said per muscle group, not per lift. This would equate to 3x15, 2-3x10 and 3-4x5 which should be manageable volume for anyone. Obviously overlapping exercises would alter the number of sets you would need. Example squats and leg ext, you would do perhaps 3x5 and then 1 or 2 sets of 5 with leg extensions.
2. If we move exercises to twice a week how are we hitting a muscle every 36-48hrs?
Evidence suggests that hitting a muscle twice in a week is similar in effect to three times a week. Remember that there are other growth indicators aside from just elevated protein synthesis and anyway, the often quoted figures of a 24 hour peak in protein synthesis and drop off to baseline at 36 hours doesn't actually apply to people with more training experience. It seems, according to evidence, that the more highly trained you are, the shorter the window of elevated protein synthesis. I wouldn't get too hung up on the 48 hour figure. With twice a week training, you are still applying chronic stimuli to the muscles which satisfies that part of the HST principles.
3. It seems big compound movements can fatigue the CNS (Deads) so how do I build up my CNS? Or is the natural progression of HST to go from compound to isolation as one gains mass, if so when do I begin transitioning?
The problem with transitioning to isolations is that it takes more of them to cover all your bases, which means that you end up doing more exercises overall since there is less overlap, so you will likely experience more fatigue. Also, single joint exercises aren't always the best for your joints. Sticking with compounds actually helps you manage your fatigue better because they are more efficient and have more overlap, thus you don't need as many different lifts to hit everything.
The solution to avoid CNS fatigue from heavy compounds, which really is only a concern with deads and to a lesser extent, squats, is to reduce frequency of that lift. This is also where alternating exercises comes into play. It is also important to keep in mind that some degree of fatigue build up is ok. If you did deadlifts twice a week for only six weeks, I wouldn't be too concerned about it, especially if your 1 RM is still less than twice your bodyweight, in which case it should be less taxing.
4. What is deloading and why can it be used in place of SD? How does it combat RBE?
I'm not convinced that strictly deloading is equivalent to an SD yet for stimulating new growth once progress has stopped.
I think what Mikey is proposing, a single day of lifting with a heavyish load, isn't really a deload and still basically counts as an SD. You should still be deconditioning adequately, in my opinion, by following his guidelines for that. Regardless, I will be testing out his idea on my upcoming cycles over the course of this winter and I will report back on how it works.
I would recommend sticking with SD although I do not think you need to do a mandatory SD every six-eight weeks or anything. As Bryan has often said, you only need to SD when growth and progress have stopped. If you are simply getting bored or tired of a cycle but are still progressing, you could just reset back to the 10s or something and that would basically be similar to a deload. I just don't think, at this point in time, that a deload will allow you to get as much new growth as SD would. I might change my opinion on this in the future.
