“If you can see it, you can do it,” an old cliché that describes envisioning your goals. A new study conducted at Ohio University has taken that saying to the next level, and found that mental visions of exercise possibly play as critical of a roll in muscle growth as actually exercising. The study put casts around participants’ wrists and divided them into two groups. One group would spend five days a week doing mental exercises—imagining their wrists were going curls when they were really still in the cast—the other group did nothing. When the study was over both groups had weaker wrists but the group that did the mental exercises wrists had degenerated less—just 25 percent compared to 40 percent of the non-exercisers. So I guess it is all in your head, or at least around 15 percent.