Those who are cynical often say that when it comes to nutrition and exercise, there is nothing new and exciting. Such people clearly don't view the ongoing research on these topics, since in fact the amount of new information about exercise and nutrition is extensive and constantly growing. Aspects of exercise that are common today were completely unknown when I began training over five decades ago. Terms such as "periodization" meant as much to us back then as Latin proverbs. Indeed, the concept of periodization, which involves dividing training into separate phases throughout the year with varying emphasis on strength, endurance, and fat loss didn't emerge until much later thanks to the work of Russian sports scientists. But we did have crude forms of periodization in those days. While the division of training wasn't as precise as it is with current periodization cycles, we did divide training into "gaining" and "fat loss" phases that involved entirely different styles of training and nutrition. For example, for about half the year most bodybuilders in the 60s and 70s would try to gain additional muscular size and strength. This was often known as bulking up. It would involve eating a lot of food for the purpose of gaining weight. If done judiciously, much of the weight gained was muscle mass. We didn't know it back then, but eating in this manner; that is eating a lot of food, promotes the release of insulin-like growth factor-1 (IGF-1), an anabolic hormone thought to produce most of the anabolic effects associated with growth hormone. So we were in an anabolic state without realizing it. But the effects were obvious since the added bodyweight that resulted from bulking up usually meant a greater strength level. With that added strength you were able to lift heavier and this meant added muscular size. The trick was to try to keep most of that added muscle mass when you decided the begin the next phase of training, which was the fat-loss phase. That phase usually involved either a reduction in total caloric intake (favored by Arnold Schwarzenegger) or a drastic reduction in carbohydrate intake. Such dieting practices led to effective body fat loss, and if a high protein diet was maintained you kept most of the muscle mass you gained during the bulking phase.
In regards to training, the accepted concept for years has been the Progressive Resistance Principle. Progressive resistance involved regularly attempting to increase the amount of resistance or weight used during training. Unless you prodded a muscle through the added stress of more weight, no gains occurred. There were other ways of manipulating training besides adding weight. You could change the frequency of workouts, such as training more often. This could be problematic since it could easily result in overtraining. I experienced this when I was told by a well-known champion bodybuilder . . .