The Martinez Academy shared this video on social media. It briefly illuminates the neurology of practicing a task, and underscores why we train in a particular manner.
(Really, myelinization is more interesting than it sounds — I hope Doc approves!)
Columbia Classical Fencing, LLC 
It isn’t quite that simple, there are subcortical connections, particularly in the cerebellum which change with learning, but the changes in myelination, WHICH MAKE SIGNAL PROPAGATION MORE EFFICIENT ARE ON the mark. The imagining is a well-known technique which can be very effective, as per the vid.