Today, it can seem like strength training and endurance training are two opposite ends of the fitness spectrum—almost like dueling political parties. Endurance athletes too often treat the weight room like it's full of hot lava, and weightlifters can view cardio work as a necessary evil at best. But Arnold recognized that the elite bodybuilder trains in a unique middle ground between strength and endurance, and he used this knowledge to his advantage on leg day in particular. He writes in "The Encyclopedia":
"It isn't enough just to subject the legs to heavy overload. You have to use heavy weights and sufficient volume of training that you stress the fibers involved and exhaust the endurance capacity of the leg muscles. Doing 5 sets of barbell curls for the biceps can be demanding, but doing 5 sets of heavy squats with 400 or 500 pounds on your shoulders is more like running a mini-marathon, with that kind of total exhaustion squeezed in 8 or 9 minutes of concentrated efforts...
"For many years, I only did 5 sets of squats when I really should have been doing 8 sets. I did not include enough front squats and, I now realize, I did not put enough weight on the leg press machine. Once I realized my mistakes and corrected them, my thighs began to grow thick and massive. I accepted the fact that leg workouts simply have to be brutal to be effective. This involves a mental effort almost as much as a physical one."
Six weeks into this trainer, you should know the type of brutality he's talking about. If not, you've got 8 sets of front squats on the lineup to remind you.