Josh Waitzkin, in his book The Art of Learning, relates a story that demonstrates the power of the mind/body link, and how everything is connected. After breaking his hand 7 weeks before a major martial arts tournament, his doctor told him he would never be able to compete. His arm would atrophy in the cast.
Instead of accepting that fate, he kept training. And whenever he did strength conditioning on his good arm, he would then visualize and imagine the workout passing to the muscles on his immobilized arm.
When his doctor took off the cast 4 days before the tournament, his arm had hardly atrophied at all, and he was cleared to complete. The doctor couldn’t believe it.
This lines up with other research into visualization and practice, though that body of work focuses on final performance metrics, and not actual physical changes (or lack thereof) in the body. At least that I know of.
More related might be the work pioneered by Dr. Ramachandran in his treatment of people with phantom limb pain. Even though the nerves no longer exists, sensation and pain can still exist. But when using a mirror apparatus that provided the patient with the illusion that they were moving the limb that no longer existed, the pain would gradually go away.
The mind/body (and soul?) link is endlessly fascinating. We’ve only barely scratched the surface of the potential repercussions.