You can see that he has thick black hair, fair skin, weak body and fragile heart. Later, in order to become stronger, he began to exercise day after day and year after year, and finally made his muscles reach the extreme. After the success of Muscle Fortress, he began to be active in major competitions, and finally turned to the hero industry to fight against weirdos. (The picture below shows him after exercise. )
Originally the black light of ordinary people, there is no doubt that it broke through the limiter and reached the level of dragon. Then the question is, why did Saitama, who was originally an ordinary person, break through the limiter at a speed and limit far beyond black light? Obviously, the intensity of exercise is completely inferior. Listen to my analysis:
First of all, we can't just look at the superficial psychological resilience. Saitama can not only gain such great strength through exercise, but also constantly do the work of repelling weirdos during the exercise. Compared with black exercise, Saitama began to retire weirdos long before ordinary people. It can be said that all kinds of men who walk through the training ground are not only physical breakthroughs, but also spiritual sublimation. The continuous fighting in the past three years has caused him to continue. Fighting is the quickest way to break through the limit. There is a miracle between life and death, and the hungry wolf can testify.
There is also black light, hehe, as long as he breaks his defense, he can collapse to show you. He is not so much a hero as a Hercules who plays hero games, and has no muscles at all. After being defeated by the hungry wolf, he was even afraid of fighting until he quit the hero industry, which shows his spiritual weakness. And Saitama is a far cry from it. It is his limit to break through a little bit of limiter by exercise.
Indeed, the intensity of exercise is 10,000 times that of Saitama, but the number of times to break the limit is probably the other way around. Compared with Saitama, who just exercises and pursues comfortable victory, as mentioned above, Saitama is trying to become a hero, although only because of his interest, but he is undoubtedly the kind who tries his best and is fearless of life and death. This can't be compared. In other words, personally, I think Saitama's exercise can cast a few streets of black light. And Saitama, after constantly breaking through the limiter, finally touched a certain field, even if he didn't exercise, he became stronger (remember the radio play, today's Saitama killed yesterday's Saitama)
Of course, having said so much doesn't rule out that Saitama's essence is just a spoof. After all, Superman with one punch was originally just a person's practice, so it is normal to set contradictions.
That's all my answer. I hope I can help you. Welcome to discuss if you have different opinions. After all, it's anime. Just be happy.