I think visualization has been shown to actually improve performances, which is not that much of a stretch, really (IIRC, a study on power lifters, I can't find it back, something Greg Nuckols wrote).

At virtually any level, performance is a function of one's physical condition and one's coordination. Even joggers will get better and more efficient at running simply by doing so repeatedly, regardless of their physical condition improvement (just like I get better at playing challenging video games, and it's not about the muscles in my thumbs). In other words, there are many non-physical factors to performance.

Visualization surely help to trains those. But yeah, not a superpower :(