The only problem with strictly focusing on heavy low rep training that leads to myofribrillar hypetrophy is that it isn’t very dramatic after a certain point in time.
So, we must recognize that muscle growth and physique development doesn’t just come from gains in strength and a bunch of calories. There is another component of muscular growth known as “sarcoplasmic hypetrophy.” This is the type of muscle growth we often associate with higher volume and higher density training (think higher reps (8-20), more sets, and shortened rest periods) This type of training creates an environment for sarcoplasmic hypertrophy which is more simply thought of as the “swelling” of a muscle cell. The swelling effect typically occurs as a result of an increased capacity of the muscle cell to store metabolic substrates within the cell – namely glycogen and water.
Often this type of hypetrophy as referred to as “non-functional” in nature because there is no direct impact on force production save for a maybe a few minor changes in the leverages around a joint. But there is another problem with this type of training that makes it hard to utilize in conjunction with a true strength-building type of program.