What does using 100% of your brain power mean, for anyone? Well, I can tell you what it doesn't mean. It doesn't mean that there are parts of your brain that you don't use. I'd like to make that clear: you use all the functional parts of your brain during any given day.
So if you use all of your brain, don't we already use 100% of our brain power? Not quite the same, and let me explain why.
Muscles cover our bodies literally from head to toe, and it's safe to say that most of us use all of our muscles at any point during the day. But do we use all of our muscle power? Do we even know the extent of our true muscle power?
For most, we're not even close. Think of it like this; if you pick up a soda can, you use the whole muscle, but only a few nerves contract the muscle so that it doesn't need to use that much energy. But if you pick up a large couch, your muscles will contract much harder in order to move the larger object. The isometric training that I perform teaches you to voluntarily contract your muscles at their fullest potential.
It's sort of the same with your mind. You may be using your whole brain, but the wattage could be much higher. You can train your mind to boost itself to its full power potential through visualization. Just like you may not know how to fully contract your muscles, you may not know how to fully use 100% of your brain power.
A horrible piece of advice to a kid is "Stop daydreaming." What you see as a potential distraction from the other things the kid is doing, you're hindering that child's natural ability to visualize their mental surroundings and goals. Fortunately, you can tap back into that ability through visualization training.
When you truly visualize, you should train to engage all of your senses in your visualization. For instance, if you are visualizing your training before you enter the gym, imagine that you are already there. A true, experienced daydreamer will already have this down, but perhaps you need some recap.
How does the gym smell? Is it crowded, and does the crowd affect your energy or focus? How does the weight feel; does it feel light and warm, or cold and heavy? What sounds surround you? Do you hear music, the distant A/C, or grunting that's decidedly reminiscent of a silverback gorilla? Do you smell and feel sweaty? Does that affect your grip? What taste is in your mouth; is your mouth dry? Are you hydrated?
Once you've created the full scope of your scenario and environment, mentally control it. Turn that scenario into something with the best possible result: you're hydrated, focused, warmed up and ready to show the iron who's the top dog. Then go be the top dog, because that visualization will help your lifting ability by leaps and bounds.
It's all in the mind, my dear Watson.