You say you do a full body workout. If you don't mind, I'd be very interested in reading what a typical workout is like, how long it takes, and how often it is done.
The fine tuning of HIT is probably the very hardest part.
I was introduced to HIT via the writings of Mike Mentzer, and the logic of it really appealed to me... but Mentzer never allowed for the idea that his theory might not be totally inclusive of all the factors involved. Arthur Jones took a more practical/empirical approach, which is probably best, because as any scientist will tell you: experiment is the final arbiter of reality.
I started HIT at 16 (after a three year plateau on very high volume training) and made frighteningly fast progress (15 lbs in six months).
Through my twenties I continued cutting back and cutting back till I was literally training only three or four sets every three days:
Day 1 -Chest (4 sets)
Day 4 -Delts and Triceps (4 sets)
Day 7 -Back (4 sets)
Day 10 -Biceps (3 sets)
Day 13 -Quads (4 sets)
Day 16 -Calves and Hams (4 sets)
...with two full days rest after each workout, I was only training bodyparts twice a month and the muscle soreness was absolutely incapacitating. I was slowly plateauing again, but I had reached what was considered the natural limit; FFMI (Fat Free Muscle Index) so I pretty much resigned myself to no more progress.
Then I considered trying Arthur Jones' approach... and that worked wonders: full body workouts; NO muscle soreness; and lots of supposedly impossible progress.
In fact it worked so well I had to cut back again and again to keep making progress.
Below is a routine I used to do 3 times a week, but progress necessitated cutting that back so now I'm only training one and a half times a week.
Here's my routine:
(warm-up) Bench Press: 2 sets x 10 reps
1 set -Bench Press
1 set -Dumbbell Flyes
1 set -Narrow-grip Dips
1 set -Close-grip EZ-bar Bench Press
1 set -EZ-bar Bent-over Rows
1 set -Close-grip lat-pulldowns
1 set -Bicep curls
1 set -Stirrup-grip Cable Curls
(warm-up) Barbell Squats: 1 set x 5 reps
1 set -Barbell Squats
1 set -Barbell Deadlifts
...this last double set somehow eliminates muscle soreness and boosts recovery by over-stressing the hip-flexors. Don't know why it works, but it really works.
...so three light warm up sets altogether; 10 work sets total and about 45 mins per workout. No direct trap work, no direct ab work; no direct forearm work; no direct hamstring work; no direct delt work; no direct calf work.
I don't bother with rep cadence but I do ensure I'm not throwing or dropping the weight (no ballistic reps). I don't do any forced-reps; negatives or drop sets... instead I just trained myself to put more real effort into my sets, meaning I usually faint and/or puke at the end of every workout.
Of course, this type of training is pretty tough... I train Monday and Friday one week, and only train Wednesday the next week.
Unusual...? Yes. Unorthodox...? Yes. Productive...? Fuck yeah!
When I started this type of very reduced training (a year ago), I usually managed 225 lbs x 14 reps on the bench... now I'm pushing 225 lbs x 20-22 reps... my squat is up over three plates (full depth; ass to the grass with a stop at the bottom) and my deadlift is up to 450 lbs (ten slow reps with a stop an inch off the ground on each rep and a properly arched back).
Okay, I like chocolate and don't do enough cardio... okay, I'm 20-23% bf... but I'm 220 lbs at 5'5'', and when I trim down for summer expeditions I'm usually a really solid (hint of abs) 195 lbs.
Hope this helps pellius.
The Luke