Have you seen that guy's forearms? His practice routine definitely shows.

Have you read his little black dot articles? A lot of his practice is discipline. One thing he actually suggests for practice in them is doing a vibrato on one unchanging note for an hour doing it every way you can imagine and without letting your mind wander to [i]anything[/] except how you are vibrating that one unchanging note. That doesn't take a whole lot of muscular effort compared to most of what he does, but you gotta admit that would give you some serious discipline.

Just in case you're thinking he's insane right now, he doesn't recommend people start out with an hour, he suggests starting with something smaller like a few minutes and working your way up.

That reminds me, I need to get some practice time in today. I haven't been practicing anywhere near enough the past couple months.