Tell me about these so-called rest days

i don't believe in complete rest days. You can take it easy, but there is really no point in taking an entire day off to just lay around all day.
Go on a walk, do some yoga, clean the house. do SOMETHING. Just don't do anything to difficult.

It's not about being lazy or laying around all day. Your muscles need at least a day to recoup and heal themselves, this is how you build muscle. If you don't want have a day off, which I get, make sure you work different groups on different days. One day work on your legs/butt and the next day work your arms or abs etc. This way your legs get a break but you're still working out. Otherwise you're going to hurt yourself and not be able to work out for days if not weeks while you heal from an injury. Google it and I swear you will find 1000 hits from personal trainers and health experts telling you the same thing.

And like the other girl said, do something light like yoga or stretching. Good luck!

....because I honestly do not want to take them, but I noticed the last two days that my legs got tired very fast - I had been doing an hour every day of Dance Central and the last two days I could only do a half hour before my leg muscles were just too tired to continue. I substituted a walk for the remaining 30 minutes (and went a little longer than 30 because walking isn't quite so much of a workout, even when I run for the first minute).

So tell me about the science of rest days - why are they so highly recommended? What's the big deal with pushing through and keeping going (since I'm unlikely to injure myself - when my legs are tired, they're tired and they stop moving)? walking is still resting right?? (>_> I mean its LESS strenuous)

There are two caveats that I can see from your post. First, "rest days" should be auto-regulated based on how you feel, sticking to a prescribed number is a little silly because we're all different, have different work capacties, and recover differently. On the other hand, do the same type of exercise for the same body parts day after day is not a good idea, as you can see your legs are tired.

If all you're doing is cardio consider alternating your cardio between low intensity and high intensity sessions. Do you do any weight training or anything? You can also use plyometrics (jump squats, broad jumps, plyo push-ups) to help vary things up.

I wasn't taking rest days and it back fired on me. I was doing intense workouts and I was hitting my daily calorie goal including my exercise calories (I have a HRM so I knew exactly how many calories I was burning), yet my body fat percentage went up! I was devastated and not to mention frustrated! From the research I've been doing and from what others said, my body may have gone in fat storing mode (just as it would if you didn't eat enough) because it was preparing for a major depletion of energy/calories! SO, from my opinion, give your body a break!

This is like saying you can lay in bed and watch TV all night and it's similar to resting because it's less strenuous that work or school.

You can do less strenuous workouts on some days, but I'm going to tell you why you don't want to. The rips in your muscle need to heal. Every time you continue to work out on your tired and worn muscles, you reduce the effectiveness of your workout, like buying used tires or charging your cell phone battery half way.

Let's say you're not convinced. Try to find a 7-day cardio routine.You'll find that the routine involves rest or active recovery.

Let's say you're STILL not convinced. You want to work out everyday and push your limits. You will find that limit. You won't just plateau, your efforts will decrease. No part of of your body will be able to run at full capacity, including your brain and your immune system. You run the risk of getting injured because your muscles can't take the extra stress. You'll be overexerting the most important muscle of all: your heart. Not to mention loss of appetite, insomnia, cardiac arrest, addiction, constant catabolism, fatigue, depression, irritability...

Your safe alternative: active recovery. This consists of low-impact workouts on your "rest" day. Not a brief 15-minute spring, but a 30-minute walk. If you want to go shopping or garden, that's fine. While you burn calories doing those things, you don't significantly increase your heart rate, so it doesn't sound like cardio to me.

If I still haven't convinced you... God rested on the seventh day. If God can take a break and get things done, I'm sure you can, too! Good luck on your fitness goals!

You wanted to know about tears in muscle fibers... here's an article that explains it: http://www.livestrong.com/article/240341-how-the-muscular-system-responds-to-exercise/

At this point you may very well want to take a rest day and then vary your workouts. In the training manner that you're using you shouldn't work your legs every day like you're doing.

Do some upper body work? Even if you don't have a gym do push-up's, ab work, something?

Do you belong to a gym or anything?

I COULD belong to a gym... I'm doing crunches 3 times a week (http://www.twohundredsitups.com) and today I have been thinking about finding some upper body exercises to do with free weights (I can pop out to the store and buy some).

The gym reeeeaaalllly doesn't appeal to me. When I think about going there it feels like a total chore - maybe in a few months or when I get to the point where working out without more equipment just isn't cutting it anymore but I'm at least a few months out from that. I was planning to start a pushup routine but I thought that might be pushing it (er no pun intended) combined with the situps and dance central -- if you haven't spent 45 minutes playing dance central you have no idea how much it works out your back and calves compared to how much sitting in a chair for 50 hours a week does. I could maybe do knee pushups without any additional strain but a) my boyfriend sits and makes fun of me the WHOLE time and b) I'm pretty sure I'm strong enough to do regular ones (but fewer of them)

Either way, I could start with knee pushups but I don't think its going to satisfy me, I'm really wanting to MOVE.

Getting into a gym or buying some home equipment is probably more optimal. If all you have now is your bodyweight you may want to look into something like this, http://velocity.t-nation.com/free_online_program/sports_body_training_diet_velocity/velocity_diet_30#velocity-training/training-program

Click on beginner program and then below you should see a Sat/Sun option, those are bodyweight exercises. There's a video to show you everything too. Even if you just do each one time it's a start. But you need to vary your training somehow because you'll run into issues like you're experiencing now and your body will stop responding to the exact same stimulus over time (plateau).

I hear that home TRX program/system is actually pretty decent, that would be a good alternative too.

Also, here's another way to have Active "Rest" days, http://www.t-nation.com/free_online_article/sports_body_training_performance_neural_charge/neural_charge_training

I think resting is good for strength training but you should still be able to do a bit of cardio each day. Taking a walk instead of dancing is a great way to "rest".

That too.

First, there's no need to be sarcastic. Here is a better link :http://www.unm.edu/~lkravitz/Article folder/musclesgrowLK.html

Second, I forget what exercises you were doing throughout the week (Wii dancing and some walking, I thought). If your exercises are already moderate and you feel too tired to complete those, then I'd say you need to fully rest. You can't completely rely on how your muscles feel. Just because you feel little to no pain doesn't mean they've completely repaired. Full rest shouldn't exclude housecleaning or grocery shopping. It's not like bed rest; just a full day with out activities that aren't geared towards fitness.

In summation: NO, you don't need to flat out stop, but it would be beneficial for you to do so. I hope this answer suits your question better.

Is that the right link? Because if so, i'm blind, I don't see that it talks about that at all.

I'm not running or really pushing myself so hard that I think I'm at risk for heart failure. Like I said, when my body tells me that I'm just too tired, I stop and do something less strenuous - what I'm asking here is if i need to flat out STOP because my less strenuous activity is still working more or less those same muscles.

And I don't believe in God (at least not the one you're talking about) so that's out too.

But I just walked over to starbucks and my body let me know that it was not willing to go faster than a shuffle, so I think I'm on forced rest today. Although yesterday I was aggressive with my potassium intake and in the evening I felt great for walking but not for dance central. So I guess we'll see.