No, the natty guy shouldn't train exactly like Schwarzenegger, but he should copy Arnold and do this.
The Magic of Training Frequency
Arnold was known for burying his training partners. He's one of the rare exceptions that possessed an extremely resilient nervous system and a fiber type that allowed him to be really strong, yet have amazing set-to-set endurance. He also had a pain threshold second to none.
Arnold was one of the rare people who could hit failure on 2 or 3 sets of an exercise and then proceed to make his fifth set the best one. He could also tolerate workouts lasting hours, hitting as many as 60 total work sets.
I don't recommend Arnold's high volume approach, but the high-frequency approach is golden, especially for the natural guy or gal. Arnold routinely hit every muscle group three times a week, which may well be the optimal frequency for maximum growth and muscle retention while dieting down.
The Benefits of High Frequency Training
- A natural lifter needs to use the workout to trigger protein synthesis. The more sessions you do (that provide enough of a stimulus to trigger the process) the more you'll grow. The trick is to trigger protein synthesis/anabolism in a muscle as often as possible, without doing too much work that leads to excessive damage (from which natural lifters can't recover from from in time), depletion of muscle glycogen (which is very anti-anabolic), and elevation of cortisol levels (which kills protein synthesis).
- Hitting a muscle more often also makes you better at recruiting that muscle. Muscle fiber recruitment is a motor skill, and just like any other motor skill, the most important thing is the frequency of practice and not the quantity. If you're better at recruiting a muscle and its muscle fibers, all of your sets will become a lot more growth stimulating.
Understand, though, that for a natural bodybuilder, volume and frequency are inversely related. You shouldn't do both high volume and high frequency. Even enhanced lifters choosing a high frequency would do best to lower volume.
What To Do
Do either a whole body approach 4 days a week or an upper/lower split done 6 days a week. With that amount of frequency, you only need one exercise per muscle group and three total sets: one set of moderate intensity to get ready, one demanding but conservative effort, and then one hard set.
Use different methods or sets/reps scheme (and exercises) on the 3-4 different sessions.