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When your grandkids’ kids go out to get some exercise in a few years, they may not be taking a ball and glove with them. Instead, you may see them skipping out the door to little Johnny or Suzie’s house with a joystick.

At least, that’s the way some video-game companies and even a few experts on physical fitness envision it.

And that idea’s actually gained some momentum with a report published last month by a University of Miami professor who found that spending some time on the tube zapping Martians may actually not be as bad for your bod as many seem to think.

In fact, according to the report, playing video games provides a slight physical workout and is not nearly as sedentary a non-activity as watching television.

Health experts concerned about childhood obesity are just the latest group to jump on the anti-gaming bandwagon.

It seems everyone over 15 has a beef with video games — from predictably neo-Luddite grandparents to the denizens of Washington, D.C.'s hallowed halls, where the crusade against video games has focused primarily on the violence and sex in such fare as "Grand Theft Auto."

The presumed negative mental or moral influence of video games has brought together such unlikely political partners as Republican U.S. Sens. Rick Santorum (Pa.) and Sam Brownback (Kan.) to Democratic U.S. Sens. Hillary Clinton (N.Y.) and Joe Lieberman (Conn.), who banded together last year to push for increased regulation on videogames.

Lieberman is known for having waged a very public long-time war against the industry, saying it’s helped corrupt youth today.

"This relatively small but highly popular minority is not just pushing the envelope," Lieberman said in 2002. "They are shooting, torturing and napalming it beyond all recognition and beyond all decency."

Historically speaking, the complaints against video games have sounded all too familiar. New media often cause a furor after they start to become popular, and the ills that computer-based entertainment has been blamed for — indolence, irresponsible sexual behavior, violence — are almost word for word the same prophecies of doom and gloom that accompanied the advent of television and comic books in the mid-20th century, and even early novels.

But professor Arlette C. Perry, chairwoman of the exercise and sports-sciences department for the University of Miami School of Education, has addressed one complaint against video games — the "indolence" claim.

In a study she conducted with graduate student Xuewen Wang, she found that playing video games wasn’t a sedentary activity, as most people had previously assumed.

Taking 21 boys between 7 and 10 who played at least 15 hours of video games a week, she hooked them up to a series of monitors do measure metabolic and physiological changes and then had them perform the kind of work most boys their age would have gladly volunteered for: They played a fighting game called "Tekken 3."

What she found was that although video-game play wasn’t nearly as active as actually going out and playing basketball, swimming or doing gymnastics, it was definitely a better option than plopping down on a couch with a bag of Cheetos and watching re-runs of "Benson."

"There’s a definite increase in caloric expenditure," Perry said. "It’s equal to walking about two miles per hour metabolically — not fast-paced, but more than sitting or watching TV. For all those researchers that lump video games together with sedentary activities and call it equivalent to TV time, that’s wrong."

Perry theorized that the exercise video games offered had to do with the enthusiasm the kids put into winning the game, but warned against those who might claim "Super Mario Brothers 2" is a replacement for going out for a run.

"While the kids are actively in combat, they’re flailing, moving their arms, actively trying to get involved in winning the came, where we see the rise in blood pressure," she said. "They’re moving, but that’s a small-muscle group, not like using the large-muscle groups, the legs. That to me is a big difference. They’re still sitting."

And she said that newer games that involved lots of legwork — such as the dancing game "Dance Dance Revolution" — might go farther in helping kids get a decent workout. She says she hopes to study the effects of that game on kids next.

Many educators may have already beaten her to the punch.

In school districts around the country, from Fort Worth, Texas, to 100 (and eventually all) public schools in West Virginia, physical-education teachers are introducing the game, known to fans as "DDR," to younger students.

It’s being touted as a novel — some say desperate — way to combat rising child-obesity rates in the United States.

But some pointed out that DDR is a relatively unique game, and that most video games hardly involve more than twitching a few fingers.

"There are a limited number of video games that can give you exercise," wrote Steven McCole, an associate professor of exercise science at McDaniel College, outside Baltimore, Md. "With ‘Dance Dance Revolution,’ at least kids are moving. Any physical activity is better than none, so a dance game is certainly better than sitting in a chair and playing a video game."

And some fitness experts were skeptical that the Perry study means much difference in the way kids will, or ought to, get fit.

"Even if you get some exercise through video games, this will not be the kind of exercise you want to encourage in your children as a healthy habit," fitness expert and author Debbie Mandel wrote in an e-mail. "Exercise should help increase focus, increase body awareness, shed stress and mellow [you] out, organize your day around good health, [and] strengthen your muscles and bones."

For Perry, exercise — real exercise — is still the best option, she said.

But for a slothful youth who needs to trim down, getting in a half hour’s worth of "Mortal Kombat" may be better than sitting around and watching "Andy Griffith" or — horrors! — reading a novel.

At least until the little ones develop a sudden interest in the decathlon.

"Parents should try to get to use this as a transition phase to get their kids away from the TV set where they sit and eat and actually do absolutely nothing," Perry said. "It’s an interim phase toward getting them out of the house and engaging in more active exercise."