A cool study showed that mental imagery (visualisation) improved muscle strength.
Your personal mental dojo can be used in many more ways that we can currently imagine.
They mentioned “Imagery ability, motivation, and self-efficacy” as the three main points to work on for more results.
The ability gets better with training, the motivation is searching the reasons you do this (it can be as simple as because it’s fun) and self-efficacy is the details you go into during the visualisation (feeling lifting a weight, forming all the details around a movement etc).