There's no shortage of products and methods available right now promising to help Americans get in shape - bulky exercise equipment, fad diets, weight-loss programs. But how about playing a video game to shed those extra pounds?

That's the thinking behind Wii Fit, Nintendo's latest offering, which aims to blend the fun of a video game with the health benefits of a regular exercise routine. Ever since Nintendo launched the Wii in November 2006, one of its most important goals has been to make gaming more physically active and, in the process, draw in new players by going beyond the stereotype of couch potatoes staring vacantly at a television screen. The system is sold bundled with the game Wii Sports, which lets users play a round of golf or tennis by swinging the Wii remote around like a piece of sporting equipment.

But Wii Fit, an $89.99 game due for release tomorrow, takes this concept even further. It comes packaged with an accessory called the Balance Board, which looks somewhat like a wide, white, plastic scale, and reads the body movements of the player standing on top of it. Included among Wii Fit's features are yoga lessons, calorie-burning aerobic challenges, and games designed to improve balance and posture. And just as important, Wii Fit asks you to weigh yourself every day in order to see how regular exercise and eating properly affect your body, while the game's mascot (an animated Balance Board) offers health tips and congratulates you on meeting your fitness goals.

For its part, Nintendo insists that Wii Fit is not meant as a replacement for regular exercise or spending time outdoors, but hopes the game will encourage players to start thinking more about their own health. With that in mind, I decided to show it to a few fitness experts and find out how it measures up.

I took the game to the staff of Excel Physical Therapy & Fitness, an outpatient physical-therapy clinic and fitness center in Glen Mills, and we tried out the various activities together.

The introduction for Wii Fit asks new users to weigh themselves and take a balance test. Right away, the staff members were surprised and impressed by the game's visual feedback for the player's center of balance and how shaky he or she is on each foot.

Physical therapist Cam McCormack, 29, explained that usually, measuring the center of balance required the use of devices called "force plates," which gauge whether a patient's rehabilitation is improving. But it can cost tens of thousands of dollars.

"Regarding the center-of-gravity exercise test, if I look at somebody doing a squat, and it looks symmetrical, but the pad shows that they tend to favor the left side, then we'd have more visual feedback to correct the problem more rapidly. . . . I think this could have tremendous rehab potential."

McCormack conceded that, while the Balance Board seemed accurate, it would need to be tested against a force plate in a laboratory to confirm the results. Nevertheless, the staff gave Nintendo high marks for providing specific feedback on balance, posture and body movement, rather than just vague scores about whether a player was improving.

Amanda Vihlen, 33, a fitness consultant and personal trainer, was next up as she tried out the Tree position in yoga. She thought the game provided clear instructions that could benefit yoga beginners. "It definitely will show where your balance is off and what you need to work on as far as strengthening different muscles."

Excel co-owner Jeff Ostrowski, 46, was called upon for one of the most physically strenuous of the game's challenges: a push-up competition against a virtual trainer. The exercise was made even more difficult by the narrow width of the Balance Board, which Ostrowski had to grip as he completed the exercises. "It's not your conventional push-up - most people tend to do them wider."

Vihlen further explained: "It's working your triceps rather than your chest and back, and because that's a smaller muscle group, people are going to be fatigued a lot more quickly." The staff said they liked the fact that the game provided a steady rhythm for doing the push-ups.

It was my turn with the game, and I chose the Basic Run mode - I jogged in place while my character on the screen kept pace with me as he strolled through a virtual park. Vihlen thought the cartoony characters and scenery provided good motivation for inactive children, but felt adults might be bored and would be better off going outside.

Thankfully, Wii Fit is not all grueling exercises. It also has a number of games that seem destined to become party favorites. There's Soccer Heading, in which the player leans left and right on the Balance Board to head-butt incoming soccer balls, or Hula Hoop, where the player swings his or her hips in a circle while simultaneously trying to catch more hoops.

While Soccer Heading seemed more of a game than an intense workout, Vihlen was enthusiastic about the Hula Hoop challenge. "I felt my quads working. You're basically in a squat position for three minutes, so they burn a little bit. But it's great fun."

I asked the staff if there was any possible risk that people might worsen their posture or throw their backs out. "In a healthy population, no," McCormack said. "But for somebody with hip or knee arthritis, that exercise would not be a good choice."

Another game, the Tightrope Walk, received mixed reviews. Vihlen saw little benefit for improving posture, but McCormack thought the game might help senior citizens who are at risk for falling and should practice their balance.

Wii Fit also offers step-aerobics sessions. They were fast-paced and could definitely burn some calories, but the staff pointed out that good step aerobics usually require elevated risers that, unlike the lower Balance Board, simulate walking up and down stairs for a tougher cardio challenge.

So what was the final verdict on Wii Fit? By the time we had tried out a bunch of activities, the staff was pretty impressed.

"I think it would be great for children," Vihlen said. "And for rehabbing patients here as well."

McCormack agreed. "For the average couch potato, the people who have no exercise knowledge, I think it's a great introduction."

Maybe after years of being criticized for creating sedentary players, video games are about to launch a health craze of their own.