I find that most fans of HIT eventually get down to working out twice a week with something like 6 exercises for one work set. They come to realize that's all they can do if they are pushing every set to absolute failure. Is this working out in an optimal way though? If you want I can cite the study but one university back in the day wanted to see how many calories were used in a typical 12 machine Nautilus work out to failure. They found they averaged 174 calories. Doing that twice a week doesn't sound like exercising to me. Now imagine the guys that preach 4 to 6 exercises twice a week because they train so (intensely)? They must severely diet because they are not getting into condition from exercise. I don't want to get into the HIT vs volume debate but I will leave it at this. If intensity was the magic bullet we would all warm up and aim for a one rep max for every exercise because that would be the most intensity anyone could do. One thing is factual. Arthur Jones was an out of shape shrimp who weighted under 150lbs most of his life. Those few pictures of him at a claimed 200 plus are not impressive. Another point is how strong can anyone get? If you started with 20lbs dumbbells for curls after 30 years of training are you using 100lbs for curls? Of course not. Training for a lack of a better term muscular endurance can take you further in terms of achievement goals.
No, I don't think that training twice a week is optimal if you want to build your body. Remember, at this stage, I am weighing the pros and cons. How much meaningful benefit I would get training more versus time lost from other things I want to do with my life. When I think back to my old training buds from the 1980s nobody, other than me, have kept it up .
I don't know how many calories I burn in my hour to hour and a half workout but I do know this: if I don't gorge myself with calories on a workout day I will lose ten pounds over night versus my usual five pounds (weighing just before going to bed and weighing first thing in the morning). This usually entails consuming a quart of ice cream in addition to whatever it is I'm eating. I choose ice cream because I don't like to stuff myself but ice cream goes down easy. Oh, and it also tastes good. So for example, after training and heading to McDs, I had my double QP with cheese, fries, apple pie and the finished it off with a quart of Dryers Rocky Road ice cream which I picked up at Foodland on my walk to Mcd. And if you even casually follow any of my posts, I am hardly severely dieting having been known to fight to the death defending my QP with cheese from any would be marauder.
On another point, don't conflate an intense rep with an intense set. While it is true that you have reached failure on a one rep max because you cannot complete another rep. But just like I said before, when I reach the point of positive failure that's when I tell myself that now it starts. Now is when you are trying to go beyond your normal functional ability. Trying to do something that you were not able to do before to stimulate an adaptive response. These are the intensity variable. So say your ORM max is 200 lbs and you fail at the 2nd rep attempt. This just means you can't generate 200 lbs of force. But I'm sure you can generate 195 lbs, and with each succeeding rep as the force you are able to generate goes down, intensity goes up. So it is these intensity variables: forced reps, drop sets, pre-exhaust... that increases the intensity and "inroads" into the muscle. Digging deeper into the training muscle getting at fibers normally dormant unless taken to complete exhaustion.
When Author Jones trained he developed quite quickly. Actual HIT training is hard and gets harder when you get older. I think it's a mistake to correlate a person's actual accomplishments in a given endeavor with his ability to coach or knowledge of the game. I don't think Freddie Roach or Cus D'Amato could box themselves out of a wet paper bag or that Ronnie Coleman or Phil Heath would make good trainers.
