I think Karin hit the nail on the head with this one. Her explanation is one that I often use with my clients. I’ve seen this in practice. I may introduce my client to a new exercise that’s moderately difficult to perform (usually balance or stability exercises), and we may not do that particular exercise for another two weeks. Every time… When the client does the exercise again, his or her body seems to “remember” how to perform the movement. My clients are always excited to see how easy it is for the human body to adapt to exercise. Little experiements like these can be real motivators for clients.