I don't think this is true at all.
At slow, manageable tempos, you can afford to use motions that don't scale to fast tempos. If you only ever play "what you can manage" with meticulous, tiny BPM increments, you'll never have to take the leap of faith and most likely will hit a wall, never getting past like 120-130 BPM 16ths comfortably. Don't ask how I know this.
What got me past that point was short bursts at BPMs way past my comfort zone and building synchrony _after_ I stumbled upon more efficient motions that scaled. IIRC, this is what Shawn Lane advocated as well.
I recommend checking out Troy Grady's (Cracking The Code) videos on YouTube if you're interested in guitar speed picking. Troy's content has cleared up many myths with an evidence-based approach and helped me get past the invisible wall. He recently uploaded a video pertaining to this very topic[0].
> What got me past that point was short bursts at BPMs way past my comfort zone and building synchrony _after_ I stumbled upon more efficient motions that scaled.
This is actually pretty close to what Stetina says. I just probably didn’t do a good job expressing it.
You’re oscillating above and below the comfort zone and that iteration like you say affords insights from both sides, and eventually the threshold grows.
Great suggestion of a video, I’ll check it out.
Depends on the instrument. For wind instruments, the motions basically don’t change, and your focus is on synchronizing your mouth with your hands. Tonguing technique is different at high speed but you would typically practice with the same technique at low speed when learning a fast piece.
This was how my daughter’s virtuoso violin instructor taught, after a lifetime of teaching.
His method was to play alongside the student at 100x their skill level, pushing against their idea that it was too difficult.
But they’d play it, at tempo, horribly, from beginning to end. And then zoom in to a section and begin improving a few phrases at a time.
It was wild to watch, because after months of this, my 11yo could do something that seemed impossible.