When I wrote earlier this year about how video games might prove to be a good on-ramp to the world of exercise, I couldn't find any studies looking specifically at the Nintendo Wii's games and how they stacked up (from a fitness perspective) against the sports they are based on. That's now changed. The American Council on Exercise has just released a small study suggesting that the Wii Sports games are better than sitting on your butt but not as good as doing the sports themselves.
In descending order of caloric burn, Wii's version of boxing burned an average of 7.2 calories a minute, tennis burned 5.3 calories a minute, baseball about 4.5, bowling about 3.9, and golf about 3.1. (That means 30-minute workouts burn 216, 159, 135, 117, and 93 calories, respectively.) That's less than the real-life activity in all cases; real bowling actually burns about twice as much as the Wii version. And only Wii's version of boxing counted as strenuous enough to meet the ACE's guidelines for endurance-building exercise.
It's also important to note that the 16 twenty-something volunteers who participated in the study were told to mimic the real games as much as possible with their arm movements—my friend who tried Wii tennis said she quickly learned you could play with just a tiny flick of the wrist, not the broader strokes you use on the actual court. So if you plan to use the Wii games for exercise, pretend you're Rafael Nadal or Michelle Wie (note to Nintendo: Sign her to an endorsement deal) and put some muscle into it.
The study looked only at Wii Sports; the ACE says a study of the newer addition, Wii Fit, which I wrote about a few months ago, is underway...though the people in the commercials look awfully slow-moving to me.