A more controversial example (since it includes foreign substances) would be PCP, but it's a similar story. A single man suddenly seeming to gain the strength and endurance is not because the drug is somehow physically changing him - it's just shutting off various critical systems like pain detection. A similar story to the above in that we are physically capable of vastly more than our bodies consciously enable, but the consequences usually involve pushing your body past its physical limits which can result in self injury.
But yeah I've also noticed the exact same thing you mention with visualization and lifting. It'd be interesting if visualization somehow helps us, even if slightly, consciously override our subconsciously enforced performance limits.
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 :(
Believing you can do something is often said to be a prerequisite to achieving it. Exactly how much it matters to the outcome I’m sure is up for huge debate, but small and large things alike in your day can be measurably impacted by your mental state, and visualization is an extremely effective way to alter your mental state in a given moment.
Weightlifters (even non-pro) will be able to identify with my own experience in reaching new PRs. Muscle activation in particular is some percentage physical and some double digit percentage mental. If you know you can lift that weight, it just doesn’t feel as heavy.
I’ve read that athletes often visualize their performance very viscerally to prepare their body to perform a routine. Reading the passage about a basketball dribbler thinking of himself being able to literally pass through other players on the court, to me is just a form of this positive visualiation.
To take it a step further, someone visualizing all that negative energy, turning it into a semi-controlled form of mass hysteria, absolutely has a significant physical effect on the people participating, and very likely also the people watching nearby.
The idea that this could work on a physically isolated subject who is unaware of the experiment would be the true revelation, but it is yet to be seen.
We do have “superpowers” in many ways, but unfortunately the laws of physics put somewhat of a damper on macro scale spooky action at a distance.