It all boils down to this: the ratio between the size of a muscle cell and the number of nuclei that it has. You see, the use/abuse of anabolic steroids leads to a higher number of myonuclei than what can be achieved naturally. When a muscle has been subjected to deloading, or to resting and consequently shrinking, as the case has been with Kevin (since his retirement from the sport)..., when he resumes training, as we're currently seeing the former champ doing, he will quickly return to his previous muscle size and strength. Why is that? Because the muscle is simply seeking to maintain the relationship between the number of nuclei and its size, hence it will respond quickly to stimuli.
All of us here on Ausbb know that it takes less time to recover lost muscle mass than it takes to surpass one's previous bests in muscle mass. Some prefer to refer to it as simply being a case of muscle memory.
If anyone is interested in this deep muscle building/re-building topic, and how one needs to activate those dormant stem cells/satellite cells located in the vicinity of muscle cells etc...., please type the following into Google: Ingrid Marie Egner on muscle hypertrophy.