I'm going to preface my answer by saying I am not as familiar with bodybuilding programming. However, I can answer some of your questions from a more general strength training perspective.
Regarding @Jeremy Likeness' quote, the strategy behind both power lifting and weightlifting programming is to be able to recruit as many muscle fibers as possible. In other words, do as much as we can with the muscle we have, since the goal is to demonstrate strength on a stage. As you can imagine, eventually you will have to increase the size and both types of hypertrophy (sarcoplasmic and myofibrilar) to get stronger. However, pushing and pulling heavy requires firing more muscle fibers for short bursts of all out effort.
Building muscle size requires exhausting more muscle fibers and forcing them to adapt to get bigger. There are several ways of doing that using different set/rep ranges for proper effect. Shorter rep ranges with more sets emphasize myfibrilar hypertrophy, and longer rep ranges with fewer sets emphasize sarcoplasmic hypertrophy. Medium (4-6) reps are a tradeoff and have marginal improvements in both. However, the key to this process is the overall volume.
(1 and 2) The program you chose
From the looks of the program, the loading phase is all about volume. You are probably going to be around 70-75% of your max. Any more than that and you might be buried in fatigue. You will feel tired, but you should be able to recover properly if you eat well. Introducing or increasing your creatine consumption post workout should help with recovery. This is what loading is all about. Power lifting routines have a similar volume phase that is preparatory for the next phase.
The growth phase will be higher intensity, but with the rep ranges there, probably closer to 75-85% of your max. If the weights are chosen correctly, your muscles should feel quite used but not feel so cloudy as you might in the loading phase. This is similar in concept to the "realization" phase in power lifting periodized programming. It's the bodybuilder equivalent to peaking. The cardio is there to help keep fat in check, so don't overemphasize it.
(3) Deload Week
The first week of the whole cycle is just as important as the remainder. It is an active rest. You'll want to keep the weights around 50-60% of your max. That will help you keep from feeling a bit too crispy.
The challenge with high volume work, which is inherent in all strength programming, is managing fatigue. Muscles grow when they are at rest. You still have to put demands on them, but sleep, active rest, etc. are a critical part of getting stronger. You need to give your muscles opportunity to grow.
(4) Length of workout
Some of the bodybuilding articles, and some power lifting ones as well suggest 1:00 hour as the optimal training time. The reason is managing cortisol levels in your system which is catabolic. Those articles have 90 minutes as the outside length of time.
That said, you also have the option of splitting the work up into multiple 1 hour sessions per day to stay inside that training window.
I would highly recommend running a program as written for at least one cycle before changing it. This goes for any program you choose.
(5) Avoiding Plateau
This is the challenge we all face. Avoiding plateau is essentially managing the stress/recovery cycles of supercompensation (i.e. getting stronger/bigger) properly. It is particularly difficult when you are dealing with a program that can bury you with fatigue.
Pay attention to how well you can think, and how you feel session to session. Take notes in your training log. If you feel like you are getting weaker, or you are finding it harder to concentrate throughout the day, fatigue is winning. You will want to back off the weight a bit while you are training until you are clear headed. Sometimes the fatigue is masking the strength you have.
I recommend coming up with a rating system for how you felt during training. Some days are better than others. A friend of mine has a 4 point rating system:
- Training really sucked. Couldn't do the work, felt weaker.
- Fatigued but got through the required stuff.
- Average training day. Clear headed, but nothing special.
- The training gods are smiling, you feel like you can lift a mountain--again and again.
The ideal is to string together as many '3' days in a row as you can. If you live in the '3' world, you will progress at a good pace. If you feel like you are in the realm of '2' for a session cut out anything extra and just do the required work. Hopefully that's a one time thing (they happen).
The challenge is what to do with those '4' days. The best thing you can do is to avoid the temptation to do extra work. That extra work means extra fatigue, and you might be in the world of '1's and '2's for a couple weeks afterwards. A better use of a '4' day is to aim for more crisp domination of the weights you normally would be using. Move the weight with more speed, or reduce the rest between sets. Just don't add more weight or do more sets/reps than the program calls for.
The unfortunate truth is that there is a genetic limit, and laws of diminishing returns. If you are living in the realm of '3' workouts most of the time, you may find that your progress (however you are measuring it) will be slower. Not stopped, just slower. Please don't confuse slow progress for plateau.
I'll respond to your follow up questions here:
First of all, thank you very much. I have few questions about your answer. Shouldn't I use one more phase between the deload week which I keep the weights around 85%-100%? Shouldn't I start off with a week or two keeping the weights around 50%-75%? After the deload week should I rest completely for a week? Regarding the training days I misunderstood you. If I train each 3 days in a row taking a day off between I can have 5-6 workouts per week, is it okay? How much workouts should I have per week as I Starr this session? Thank you very much !
The most important thing to keep in mind is the goal you are trying to achieve at the moment. Periodization is a method to have a logical progression of goals to help achieve some final end goal. For example, power lifting periodization has an ultimate goal of a new 1 rep max in competition. To achieve that ultimate goal you first go through an "accumulation" phase (similar to your loading phase), an optional "switching" phase, and then a "realization" phase. The progression of building more base strength through volume through less and less volume to more and more intensity is a proven way to increase your 1 rep max. There's a bit more to it, obviously, but each phase has a specific goal.
The heavier the weight, the more stress it puts on your body. One of the ways to live in the '3' world (see the grading scale above) is to make sure you don't go above 90% unless you are preparing for competition. Most of your training can and should be done with lighter weights--particularly if you are trying to put on muscle size which requires a lot of volume. As intensity, or the weight on the bar, goes up; then volume has to go down to compensate. The lower the volume, or the shorter the number of reps, the more you are training your nervous system rather than your muscles.
Every successful program has a philosophy behind it and a reason for manipulating the training variables. Some guys will write books about their training methodology such as Paul Carter, Jim Wendler, and Mark Rippetoe. You can learn a lot from they similarities and differences between the programs and why each of them made those choices. The guys I referenced are all power lifters, and I have books from each of them. I recommend finding equivalent guys in bodybuilding to help understand the tradeoffs in that style of training.