Hi Joy,
Oh yes, keep your body moving on a rest week and even a rest day, stretching is a great activity on your rest day. On rest day you want to take a break from working your muscles with weights or working your heart by jumping up and down with cardio. Even a nice slow to moderate pace walk is good on rest day. Basically something light or mild, or stretching. You are actually trying to give your body recovery time, so it can repair all the wear you did that week.
As for a rest week, I personally take on between every 4 or 5 weeks. As I found that schedule really works for my body. Basically you want to take a rest week before your muscles start feel tired and over worked. Which at first can be really hard to guessimate. And rest week does not mean sit down. Keep things in the light to moderate range, I love to do a lot of stretching that week I try to add it in on 3 different days. If you do cardio keep it low, 50 - 60% of your max heart rate, this should right before you break a sweat cardio, no real sweating. Unless your hot blooded then you'll have to take your pulse instead. As for weight training, I'd recommend droping the the heaviness of the weights in half or not use them at all. As you are trying to rest and trick your body into believing this is its new easy life, and allowing it to repair and drain all the acid and water out of the muscles, so you don't want to create much more if you can avoid it.
I usually add Yoga and light cardio on alternating days, and yes I still take my rest day on rest week and that I actually give myself the complete day off with no workout or stretching. Now with Cathe's StretchMax, I'm sure it will replace a day or two of the Yoga.
Also if you notice your not getting results, or it seems like your working and its just kind of hlah, it's a good time for a rest week.
What you'll have to do to start a rest week is to experiment, try a rest week at every 4 weeks, and if it seems like that is too soon, then try it every 5 or 6 weeks. Make sure your try it twice to see as not always the first time gives you the best impression. I don't recommend anyone going more then 8 weeks without a rest week. As I haven't meet anyone who could go over 8 weeks and not actually be going down hill in their workouts. If you notice your rotating your workouts more then you use to, it can also be time for a rest week, as it can show that your muscles are getting over trained or your wearing yourself out too fast and your switching for the rush, so you can keep going. Once you start taking rest weeks its a lot easier to find out what interval works for you. As your body gets that rest week and then you see what you can do when you come out of that rest week and you can actually see yourself going a bit down hill if you wait too long.
Another way I do rest weeks is I do one before I start a new rotation, this allow me to come in blasting on the new rotation and really seeing what it can do for me, as well as what I can really push to do myself. I also find that I feel like I really accomplished something as I do a rotation have a week off signaling I finished it, I'm done and and then I'm starting a whole new workout rotation and it's more like a goal and it feels great when you hit that rest week and know you did that rotation to the best of your ablity, and you can recover and hit the nest one as hard as you can, and break your plateaus. Ever since I started doing rest weeks and actually keep them on a schedule I have never plateaued for more then 2 weeks, and it's usually that last week before I hit rest week, rest week I stay the same as the last week and then I change once I start up again. It's almost like someone turned on the light swtich.
But really set up your rest week before you take it, have an idea what your goingto do, at least you don't have to do the day by day thing if that's not your style just make sure you got the basis covered. Long walks and stretching, or a light aerboics tape that you used when you first started exercising, as Cathe's tapes wouldn't excatly fit into the *light* cardio work. Just give yourself enough not to get bored, your still working but basically at half your level, and then go for it. Once you take one or two, you will see a change and you will feel the change as well as seeing yourself kind of drag a bit, and when you see that take note as to how many weeks you went before the drag happen and make sure to take your rest week the week before the next time around. So do take a rest break some where between 4 to 7 weeks, and then play around with your activies until you find ones that really re-energize you as well as keep the muscles moving and allow your body to repair, there are a ton out there. Walking, a nice slow bike ride, Yoga, Pilates, slow dancing, slow jazzerize, a nice long hour in the Sauna, a dip in the pool (without doing many laps but doesn't mean you can't do a nice light workout), a nice dip in the hot tube, and work with and against the current, etc.
Hope that helps,
Kit