Answer: In order to compare body builders of today to Arnold at his peak you must understand the differences in science as well as the training knowledge and years of experience that the bodybuilding competitors have now vs. then.
So let’s start with the top body builders of today. The top body builders of today are some of the biggest and hardest body builders known in the history of body building. Now can we say that they trained harder today than body builders from Arnold’s time? Not really. In actuality, body builders like Arnold Schwarzenegger started training earlier in life than most body builders of today.
What you find nowadays, is science aiding in the progression of an amateur body builder’s career allowing him to become Mr. Olympia or close to it in a shorter amount of time than in the past.
Let’s talk about Arnold and body builders from his time. Most body builder’s from that era did not have the leg size that they do today. This only allowed a small percentage to make the top 5 in the Mr. Olympia. Nowadays, there are many competitors who, because of science, can attain leg size that they normally would not have been able to.
Genetics used to play a bigger role in the sport. Not to say that science wasn’t around then, but you had to already have developed most of your muscle in order to be competitive. Today, someone who’s never stepped in a gym could add on 30-60 pounds and be rock hard within 5 years. And then completely lose that muscle after retiring.
If you notice today you can find body builder’s from Arnold’s era still walking around with muscle, such Robby Robinson or Lou Ferrigno. On the other hand, a lot of body builder’s of today have disappeared or are deceased.
So in closing, Arnold at his peak would not compare in overall mass and conditioning (hardness) but that’s a science issue. It has nothing to do with genetics, work ethics or dieting. Comparing these two generations is like comparing a race car from the 50’s to a race car of today.