Power Forearms! has something for everyone. It offers the bodybuilder massive, ripped forearms. It offers the martial artist nearly impenetrable blocks and explosive strikes. It offers any athlete a more powerful grip and greatly enhanced wrist stability.
And it delivers all this in just 10 minutes a day, twice a week!
At some point you've probably been told something like this: "Since you use your forearms every time you grab, twist, or pull something, they have really high endurance, so the only way to weight-train them is to do really high numbers of reps. Anything less just won't make them grow."
Luckily, that's not true!
The Fatigue/Tension Principle
Researchers have spent a lot of time trying to figure out what makes muscles grow. They've understood pieces of the puzzle for some time - the idea of overloading, for example. We all know forcing muscles to lift more than we think possible is essential to growth.
muscle A series of sets, with long rests in between, has a fatigue curve that looks like this:
Notice that as a result of letting your fatigue level drop so low in between sets, there is no CUMULATIVE FATIGUE EFFECT over several sets; you don't get more tired during the second set than during the first, nor more tired during the third set than during the first.
Intuition and experience suggest heavier weights are required for building strength and bulk. Basically, that's true. But as we've mentioned, it's not just the weight that makes the difference.
This is not to say a high load isn't effective or necessary for inducing growth. Quite the contrary. Using near-maximal poundages has a pronounced effect on the Fatigue/Tension curve. Assuming you structure your workout to take advantage of the Fatigue element - fast pace, short rests - using heavier weights raises the entire curve. It also makes the curve peak at a higher level, because heavier weights increase fatigue as well as tension.