What is muscle memory?

Most people notice that when they start back lifting weights again after a long time off their muscles grow back a lot faster than they took to grow the first time round, this is what is talked about as muscle memory.  There is no scientific evidence to suggest that the muscles have memory and grow back a lot faster despite 90% of people believing in it.  However, the first time you lifted weights you were probably a bit hesitant when performing reps, this time round you perform much fuller movements with confidence and you increase the weights very fast as you know you have lifted more than this in the past.  The first time you trained you most likely only recruited a small number of muscle fibres but as you continued lifting you recruited more and more.  As you start this time you will recruit a similar number of fibres to what you were lifting towards the end of your training the previous time, this would make you grow faster to.   There is evidence also to suggest that blood supply to the muscles increases as you train more regularly, the blood supply you have built up from the previous time would most likely still be set giving the muscles more blood this time around allowing them to get a much better supply or branch chain amino acids to the muscles.