When I was a kid, I knew guys who were hard as nails, super strong, very possibly more fit than the guys I am lifting alongside at the gym. My uncle for example, who was a pro ball player with the Astros in the 60s, without lifting weight. It was common for major league players, especially pitchers, barely know what a barbell was. Of course, he was the fittest man in our family and still is even in his 60s (still without lifting weight for the most part).

He took me under his wing when I was a teen and tried to help me get fit. I left quickly... smoking pot and listening to the Velvet Underground was much more appealing than running in the Texas heat. But for the short time we trained together he had me doing sit ups and push ups every day - and running. No weights. By the time I was in my 20s and thought for the first time about my own fitness, we had World Gyms all over the place, muscle mags at the super market next to the Enquirer, and of course Arnold was a super star. I went straight for the weight. I haven't done a sit up or push up or PE class drills since I was in Jr. high.

The sit up has of course fallen from vogue and we do a crunch these days. Hard to see how the push up is anything other than a chest press with natural body weight and some additional muscles pulled in for stabilizing. So you could generally say these two exercises are essentially the movements my predecessors used to stay fit, but they did them every single day, in numbers of reps that today would seem extremely weird.

And in physical education class as well, the way to exercise was to do these things every day, as many as you could... not three sets of X amount, but 50, 100.... I've known guys who did hundreds of sits ups the second they got out of bed. And guys for whom the measure of strength was not the number of plates on your bench press, but the number of sit ups you can do. I knew a guy who came back from the army and used to do daily push ups with his daughter on his back. The guy was like Iron Man, and he lived on cheeseburgers and never had a gym membership in his life.

It's easy to say history has shown us the proper way, and all this endless pushing up and sitting up is madness. But I look back and know that even my grandfather who was sold drywall but began his day with pushups and calisthenics was an extremely strong man. I would have picked him any day in any test of strength over the guys who are lifting 3x a week now with protein shakes (like me).

If I took the same moves, the push up and sit up, into the gym, it would be insane to follow these kinds of routines (every day, as many reps as possible). I know, or believe, if I did presses every day I would fail to develop any strength long term, and probably would injure and exhaust myself. My uncle could do hundreds of push ups. If I did 100 presses at the gym everybody in there would think I was nuts. They might throw me out!

But abs on the other hand... I see certain people in the gym doing them daily. That's not what has been taught to me, but I know people are doing it. I've played around with doing crunches in high numbers of reps at times and doing them every day, just because I liked the rush. Other times I've included them in my weight workouts and taken days off. I have no idea which "worked better".

So the question is, what's the line between bench press and push up, between ab crunches in the gym and the sit ups we were taught in PE class? Why did people routinely do those exercises daily, for years, in ever increasing numbers.... and not just stay injury free, but develop great strength and longevity? Why did that develop super lean power without rest days. To me, rest after using weights is gospel. But what <i>really</i> will happen to me if I do my gym resistance exercises, especially the crunch and press movements, daily?

(Why do I think Nick will have a good answer for this?)

I have only heard the no weights everyday mantra with regards to building muscle ... to combat overtraining. To build muscle you need to stress the muscle, and if you are going to the limit the muscle needs time to heal, some train a muscle group 100% once a week.
Then there is HST training (still bodybuilding) which is typically whole body every other day, but seldom up to 100% training. Still with the aim of building maximum muscle mass.
If your goal is not to build muscle, but to get fit and you are not even close to stressing your muscles to the maximum, I cannot see any reason why you should not train the muscles everyday. Your muscles might never get bodybuilder big, but you will still put on muscle ...

then again, i'm no expert ;)

i agree. when you lift heavy and stress the muscles they kinda breakdown. so you need the rest days to rebuild the muscle thus you get bigger. but if you never break them down then you don't really need the rest days. if you notice runners usually run back-to-back days but their legs never get big from it just toned. if you are doing weighted ab exercises with heavy weight then you might not want to do them everyday.

but you still need rest in the form of sleep. i used to do cardio for an hour a day and sleep for at least 8 hours a night. if i didn't get enough sleep, before the end of the week my legs would get too tired to finish my cardio routine.

also, calisthenics(pushups, situps, etc) are great. the Army has been using them for years. they're the gym that is always with you.