Blanche Betten, a 76-year-old retired restaurant owner, hammered Bob Warner, 85, with a flurry of punches, sending the World War II and Korean War veteran sprawling to the ground.

"Again, again, again," onlooker Rosa Villanueva, 61, shouted at the Perris Hill Senior Center as Warner tried to regain his footing.

These seniors in San Bernardino, Calif., weren't fighting in a real ring. They were boxing on Nintendo Co.'s Wii game console as part of a public-health class to encourage physical activity. They're among a growing number of former nongamers who have taken up the Wii and made it the dominant player in the $21 billion U.S. video game industry.

"I don't know of any other digital technology today that offers grandparents and grandkids an avenue to play together or connect," said Mike Hickey, a video game analyst at Janco Partners.

Last year, 26 percent of people over the age of 50 played video games, up from 9 percent in 1999, according to the Entertainment Software Association, a trade group. The figure is expected to rise because of the games' growing popularity with seniors, the association said.

In San Bernardino County, 350 people aged 58 to 85 have participated in six-week fitness classes at senior centers since July, underscoring how the Wii has expanded the market for Kyoto-based Nintendo.

U.S. retailers have sold 15.4 million Wii players since the console was introduced in 2006, according to research firm NPD Group Inc. The 8 million purchased through 11 months of 2008 exceeded the combined total for Microsoft Corp.'s Xbox 360 and Sony Corp.'s PlayStation 3. Four of the top 10 games in November were for the Wii, NPD said.

"The holiday sales rush drained supplies in many places and we can't guarantee that every location you visit will have Wiis in stock," said Amber McCollom, a Nintendo spokeswoman in New York.

Soaring Wii sales haven't helped Nintendo stock. The shares declined 50 percent in 2008 after doubling in each of the prior two years. In October, Nintendo cut its full-year profit forecast and dividend as the strong yen eroded the value of its exports.

"Wii Fit," a $90 (roughly ¥9,000) game that includes a balance board for yoga and other exercises, was the No. 4 seller in the U.S. in November. "Wii Sports," a title with boxing, bowling and tennis, is included with every console.

Researchers and senior-center operators say waving the Wii's motion-activated joystick to throw virtual punches or swim laps may improve health.

"If it does show real benefit it could be a huge asset for rehabilitation and increasing physical activity," said Stacy Fritz, director of the Rehabilitation Laboratory at the University of South Carolina, which is studying whether the Wii can help stroke victims.

Stroke sufferers in Fritz's study, the recipient of a $200,000 grant from the Robert Wood Johnson Foundation, show up four days a week for an hour. She has noted positive results in mobility using the "Wii Fit" balance board, though she cautions the two-year study won't be done until July 2010.

"There are definitely changes that we notice," Fritz said. "One gentleman was walking with a cane when he came in, but by the end of the six weeks he was able to walk out on his own."

The foundation's Health Games Research program announced it is seeking applications for $2 million in grants to examine the health benefits of video games or ways they can be designed better to promote physical activity.

Cedric Bryant, chief science officer for the American Council on Exercise, said that while the Wii can benefit seniors returning to physical activity, traditional exercise produces better results.

"You're going to get much greater physical-fitness benefit from the real activity," Bryant said.

Health advocates hope seniors using the Wii can replicate the success Konami Corp.'s "Dance, Dance Revolution" had in reducing childhood obesity, as reported in the 2006 Mayo Clinic study. That game, also available for the Wii, requires players to jump on certain spaces to match cues from the screen. West Virginia is putting versions in its 765 public schools.

San Bernardino public-health worker Erin Haugh, 27, incorporated games such as boxing and track and field from "Wii Olympics" in a walking program she has led for about two years.

The arm-waving raises the seniors' heart rates and has made the classes more popular, Haugh said.

"My goal is to keep it interesting," Haugh said. "They are more likely to keep going waving their arms than if I was standing up there telling them to do it."