Cari Romm flags a study where small group of test subjects “had their non-dominant arms placed in elbow-to-finger casts for four weeks.” Half “were asked to perform mental-imagery exercises five days a week, imagining themselves alternately flexing and resting their immobilized wrists for five-second intervals”:
When the casts came off at the end of the four weeks, both groups had lost strength in their arms—but the group that had imagined themselves doing the arm exercises lost significantly less, measuring an average of 25 percent weaker than at the start of the study, compared to 45 percent for the group that hadn’t taken part in the mental-imagery activities. “There’s a fair amount of evidence that you’ll activate the same parts of the brain doing imagery as you do if you’re actually doing the task itself,” explained Brian Clark, a physiology professor at Ohio University and the study’s lead author. “The basic thought is that the imagery is allowing the brain to maintain those connections.”
The Dish 