The incline bench can become a problem because people try to make it a shoulder exercise when it isnt one. If you are doing certain exercises that focus on a primary muscle, and you feel the others being used more, you've got form problems.
Dumbbell presses do hit the lateral delt as a synergist, but not as the primary muscle for the exercise.
In my opinion, this is where people run into problems. They'll do an exercise, that targets one muscle, but then has 8 synergists, and thinks its all they need.
Triceps are a synergist in the DB press, but is it a Tricep exercise to focus on the tricep?
Same with the day 2 you mentioned mrRuckus. You said Triceps should be pretty much toast (out of fuel in the tank). If that is the case with incline bench press, you've got problems. The pectoralis major should be the muscle used in the incline, and again the Tricep for the synergist.
Even if you do the dips, you should have some juice left. Unless you are making the dips a Tricep exercise by the way you are doing them. You can make it a chest exercise too depending on your form.
All i'm saying is that on my routine, there are 3-4 exercises per bodypart. I hit everything I can. Sure many muscles will be synergists and used over and over, but they aren't getting targeted from that exercise. It isn't hitting the muscle in the most effective way.
The biggest thing to remember speakeasy, is that what routine may work for someone else, may not work for you.
Try it, and if it works, stick with it. If it doesn't, switch it up. I am sure everyone here has some different workout then the other person. We all are made different, and bodies respond different. Trying to figure out all of this would take you literally years if you want to nit pick.
You have exercises (MANY) you have reps, you have sets, then you have rest between sets. You have rest before you workout, you have different weights, calories, and so forth.
What if you added ONE more rep to an exercise? What if you took one more rep away? What if you rested 2min 30 seconds as opposed to 1min? What if you had 100g of carbs 1hr before a workout? What about 75g or 75g/25g protein? What ratio of carbs and % of protein?
What if you could pinpoint the precise time ATP regenerates in the body? Use that time and then hit your next set.
You see my point? You could get nitpicky as hell, and stay in a lab all day long and figure out if 5g of soy isolate added to your 25g whey and 5g egg was better before your workout.
You could see if 1 rep for you on certain exercises did any better than 1 less rep.
Truly is a headache if its broken down science wise.
My theory is DO WHAT WORKS FOR YOU. Then stick with it. I prob eat more food than guys 50lbs heavier than me. That's my metabolism, that's how my body is, so when I read a magazine and see those 2400cal diets or even 2800cal for growth, I know it wont be enough for me through trial and error.