Muscle Memory - one industrial definition
What does it mean to learn a new skill and go from "novice" to "expert"?
In the world of heavy equipment, part of that learning means memorizing how to use levers, joysticks, and even pedals in a coordinated way to control the attachment at the end of the boom.
But how does this memorizing take place?
At first, you need to concentrate in order to make your fingers, hands, arms (and feet) move in just the right way, based on what you see. What you're learning is precision, i.e. how to make the boom attachment perform the task (move a load, grapple a tree, drill a hole, etc.) carefully.
Scientists have discovered that there are a large number of internal brain structures which work together with the input and output brain structures to form fleeting images in the mind. Using these images, we learn to interpret input signals, process them, and formulate output responses in a deliberate, conscious, way.
But after a while, the "seeing-thinking-doing" gradually becomes "seeing-doing" because your muscles seem to "know" and "remember" just what to do. What you're learning now is speed, i.e. how to perform the task carefully and quickly. That's muscle memory.
Scientists call this "kinesthetic memory" or "neuro-muscular facilitation" and they speak of "sensory-motor" learning, since you are combining sensing input, i.e. what you see with your eyes, with motor output, i.e. what you do with your body.
Of course, during the "drill-and-practice", your muscles aren't really memorizing anything (since all memories are stored in your brain). Instead, what you see with your eyes is interpreted by your brain in the form of nerve signals to your muscles to make your body move.
Now by making the same movements in response to the same visual cues over and over again, the associated nerve-muscle connections gradually become more effective, i.e. the transmission of the signals becomes more effective, and this is how the "thinking" in the "seeing-thinking-doing" is gradually replaced by "seeing-doing", i.e. by muscle memory.
And this is exactly what we observe when people spend time at the controls of our Personal Simulators. At first, their body language tells you at a glance that they are concentrating carefully, working hard to watch and learn. But come back sometime later and the same people are now relaxed, sitting back, and making the same precise gestures but now much faster!
In the world of heavy equipment, muscle memory is especially important because it's the combination of care and speed that make operators truly competent. And muscle memory also let's you turn your attention to the "big picture" e.g. to plan the next step in the work to be done, by taking over a large part of your "mental load".
But there's a "catch": to learn the new skills and acquire muscle memory, you must be practicing properly. This means lots of feedback, right from the start, since novices don't know enough yet about doing things right to be able notice, and correct, their own mistakes! (If they could, they'd be experts instead of novices.) Worse, if you don't practice properly, you'll learn to do things "wrong" and down the load, you'll need to "un-memorize" those bad habits.
That's why we say perfect practice makes perfect. And here's where simulators really shine because they evaluate your (simulated) performance in ways that are much more objective and much more comprehensive than a human trainer can. And that's why the instructional design of simulators incorporate key "performance indicators" associated with both job quality and productivity.
But remember: acquiring skills is variable. Some people learn faster than others and go on to achieve higher levels of performance just because they were born with more pre-requisite abilities.
You develop "Muscle Memory" 
