"Muscle memory" may be based more on the conversion (differentiation) of certain types of muscle fiber due to resistance training. This conversion seems to not only be permanent, but there is a possibility that a lay-off from resistance training also stimulates fromation of new undifferentiated fibers for future training periods. Although the exact mechanisms are not understood, there is a very real effect of previous training on "muscle memory", and some evidence to show that we respond EVEN BETTER to resistance training by taking time off and allowing the muscle memory to kick in....