Ummm....
Do you know any kid (or anyone for that matter) that does sit-ups for hours on end?
Didn't think so.
what, sure! There's Jimmy.. and.. um.. yeah, that's a good point.
I do have to commend Nintendo for the wii though. Considering that they must have known that people will be stupid and punch themselves in the eye, throw controllers at people, break household items, play it so much that they get repetitive-strain injuries, etc. and sue their asses off, I'm surprised any company would risk it at all.
problem is most kids wont play dance dance revolution, they want to play Zena and such.
You'd be surprised by wii boxing though- i've played that till I was totally exhausted and even slightly asthmatic - I usually stop before that happens, but it was just so addictive. Getting me exhausted isn't such a big feat, but I was taking turns with my dad, and he's a really fit guy who does lots of physical work a day, and he got winded by it too.
The beauty of it is that you'll forget all about your muscles starting to feel tired when you're concentrating on hitting the punching bags in the right rhythm.
I think this aspect could be used in other ways. Say, having a bunch of exercise bicycles in a gym that are linked up, and when more than one person is riding, they're in a simulated marathon together. Ad a little strategy, like being able to knock the other person off the trail or shoot at them or whatever, and half an hour on the bike will fly by much quicker.