Volume training did NOT give Arnold most of his size. Fullbody work did. Arnold did evolve his training into using more volume, but if you want to know how he trained to make a substantial portion of his gains, read on...
This is yet another quote from Arnold Schwarzenegger that reveals the impact that Reg Park and fullbody workouts had on his training:
When I was trying to get bigger in my early days of training, I followed a routine called the Golden Six. I made tremendous gains on this program and do did many others who trained at my gym in Munich. All agreed that this simple system of training produced excellent gains in muscle size and bodyweight. Here are the Golden Six:
1.) Barbell Squats. This exercise not only develops the lower body, but it strengthens the heart and lungs while improving the general circulation as well. Use a weight that will permit you to perform 4 sets of 10 reps. Always lower yourself until your upper thighs are at least parallel to the floor, and keep your back flat.
2.) Barbell Bench Presses. This is my favorite upper body exercise, and almost every training program I've ever used includes it. Take a fairly wide grip -- your hands about 32 inches apart. Inhale as you lower the bar to your nipples and exhale as you push it back to arms' length. Don't bounce the weight off your chest. 3 sets of 10 reps.
3.) Chins. If you have limited training experience you may find chins difficult at first. If you have a lat machine, you can perform pulldowns until you've developed sufficient strength to do chins. Use a fairly wide grip and try to bring your chin over the bar. Do as many reps as you can for 3 sets.
4.) Overhead Presses. This exercise reigns supreme for widening and thickening the shoulders. I prefer to do it seated and often press behind the neck. Use a wide grip -- your thumbs about six inches wider than your delts on each side. Lower the weight slowly and don't pause at the bottom. 4 sets of 10 reps.
5.) Barbell Curls. The triceps have already been thoroughly exercised during the bench press and the overhead press. Use a shoulder width grip and a weight you can curl without any body movement. Don't let your elbows move away from the sides of your body, make sure you straighten your arms completely before each rep and do 3 sets of 10 reps.
6.) Bent-Knee Situps. It's only sensible to keep your midsection firm and toned when gaining muscular weight. Situps also improve digestion and elimination as well. Don't pause between reps and continue for 20 or as many reps as you can do without stopping. Do 3 or 4 sets.