We cannot trust our eyes (or our pain)
Pain is a lot like this — it is warped by our expectations and point of view. Unlike a clever model, though, we can’t turn it around to see what’s really going on. And trying to see through the illusion, trying to believe that there’s nothing much actually wrong with our tissues (often true), is even more difficult than seeing through these illusions.
Nevertheless, that is what therapy and rehab are all about: trying to change our expectations and point view with interesting new sensations and movements.
Aside from the analogy to pain, these are just fantastic illusions. Thanks to Nick Ing of Massage & Fitness Magazine for pointing out the video. For more about the slippery weirdness of pain perception, see Pain is Weird: Pain science reveals a volatile, misleading sensation that is often more than just a symptom, and sometimes worse than whatever started it.