REST/RECOVERY DAY:
Although rest is needed, it is still important to remain active on those days. The body, just like the mind, needs stimulation every day. Even after a grueling workout many people find it's a good idea to move around, maybe take a walk, as early as the day after to avoid stiffening up. Even people who suffer heart attacks are encouraged to get out of bed and move around as soon as possible. On rest and recovery days it is important to avoid doing the worst thing you can do for your body... NOTHING.
Examples of rest and recovery activities are walking, static stretch exercises (after a warm up and loosening up period), dynamic stretching, swimming, water running, and riding a bike.
Keep in mind that increasing respiration and heart rate to a level just slightly above normal and challenging your range of motion are generally good things to do almost any time.
Rest is a variable to apply in response to the feedback your body gives—more, or less, but always some.
