IT'S not every personal trainer who inspires a client to write poetry in her honor. But after a few weeks of training with doe-eyed Maya, Glen Raphael couldn't help but extol her virtues in verse: "Sweet Maya never sleeps or even tires/I rarely get a sense that she perspires."
Posting such ardent poetry might be embarrassing — if Maya could actually read it. But Maya is not a real person; she is a computer-simulated woman designed to be an ideal trainer. "She's my personal trainer," said Mr. Raphael, 38, a software engineer in San Francisco. "She just happens to live in my television."
Each time Mr. Raphael begins a workout, Maya asks how he's feeling and the next time, remembers whether he said upbeat or sluggish. She also nags if he misses a scheduled workout, asking, "Where were you yesterday?"
All it takes to get Maya to customize a personal exercise program is a personal computer or a video game console (PlayStation 2, Xbox or Xbox 360) and an additional $34.99 for the training game, Yourself!Fitness.
Virtual trainers in such programs come to seem real to the people who use them not only because they are designed to be affable but also because, through the magic of computing, they can actually keep track of users' progress over months. Unlike fitness DVD's that show the same exercises day after day, virtual trainers can suggest ever-more-difficult workouts.
In just over a year, more than 100,000 copies of Yourself!Fitness have been sold, a drop in the bucket compared with the mammoth sales of traditional games. But at-home exercisers, out-of-shape novices and video game players who have tried the game say they enjoy combining exercise with a video game and that, with consistent use, it helps boost fitness. Some fitness experts warn that video coaching is a poor substitute for good one-on-one training. Still, for the price of a few sessions with a trainer at a gym, people can "hire" a cybertrainer who can meet them anytime they like and who is knowledgeable about fitness.
"Everybody needs feedback, and it's a heck of a lot cheaper than paying a trainer," said Doug Lowenstein, the president of the Entertainment Software Association.
Personal training video games use various techniques to gauge a player's fitness. Before starting workouts with Yourself!Fitness, players take a test that assesses their cardiovascular fitness, strength and flexibility. Then Maya suggests exercises — including strength training, yoga, Pilates and step aerobics — that target areas of weakness. Periodically she asks the player to rate the difficulty of the drills, so she can intensify the workout if need be.
"The more input you give her, the more personalized the workout becomes," said Phineas Barnes, the chief executive of ResponDesign, which created the game.
EyeToy: Kinetic, a personal training game created by Sony Computer Entertainment Europe and Nike Motionworks, assesses a player's progress more directly. The EyeToy camera captures the player's movements and beams them on screen. The object of one game is to dodge some falling balls while hitting others with a deft punch or kick. If a player fails to evade the balls, a trainer offers advice.
Kinetic offers two trainers: either British Anna, whose coaching style is firm but polite, or her take-charge American counterpart, Matt. Both provide pointers and encouragement as they lead players through kickboxing, yoga, tai chi or cardiovascular drills like the ball drop game.
Kristen Dennis, who grew up playing old-fashioned combat games, said once she starts playing Kinetic she never quits, even if she tires. "I'm not going to stop because I know it's going to lower my score," said Ms. Dennis, 22, who is a research coordinator in the psychology department at Duke University in Durham, N.C. "I don't feel the same way about the elliptical."
Like many video games, Yourself!Fitness lets players advance to tougher challenges after they have mastered easier ones. Each workout brings gamers a step closer to hearing new music or to unlocking new virtual scenery like an Alpine retreat.
That incentive so engaged Leigh Ann Massey, 26, that she lost 64 pounds in eight months doggedly trying to land virtual real estate. After training with Maya, Ms. Massey, a veterinary student at Tuskegee University in Alabama, started going to a gym for cardiovascular exercise six times a week.
"I had to get to a certain point until I had enough confidence to go and sweat in front of people," Ms. Massey said.
Special care was taken to make each cybertrainer universally appealing. Anna and Matt are robust but not so perfectly chiseled as to intimidate their trainees. "Certain looks were eliminated because they looked too gung ho," said Tom Holmes, the lead producer of Kinetic.
The trainers' personalities were likewise fine-tuned. Their creators videotaped trainers from Nike Sport Research Lab in Beaverton, Ore., and then replicated, in Anna and Matt, the real trainers' expertise in providing both instruction and encouragement. After a sub-par showing, Matt says, "You've got a bit of work ahead of you but overall I think that was a strong performance." Or he cheers, "I like what I see!"
Ricardo Torres, a senior editor for the online magazine GameSpot, said, "It's prerecorded and canned footage, but they are speaking to you." It's "kind of cheesy," he added. "But people feel special."
As for Maya, the game creators at ResponDesign asked real trainers to evaluate her teaching skills, and focus groups helped hone her personality and appearance. The people surveyed said they wanted a trainer "athletic enough to be credible, but not so athletic that I want to turn her off because I think she's been working out all day," Mr. Barnes said.
Carly Haley, 23, from Boise, Idaho, said: "She doesn't look like a plasticky woman. She looks like me."
One player with the screen name lauradahl on a discussion board at www.yourselfitness.com said, "I find myself telling my husband, Maya and I did this or Maya and I did that." She added, "I don't know what I would do without her."
That people so value a virtual relationship does not surprise Gitte Lindgaard, the deputy editor of the journal Interacting With Computers. "We do relate very well to virtual people."
But even the best virtual interactions do not stand up to those with a good, real trainer, said Catherine Jackson, a professor of kinesiology at California State University at Fresno, because a real trainer can get to know an exerciser's motivations, and when he or she is telling the truth or lying.
Steve Edwards, an exercise psychologist and a professor at Oklahoma State University in Stillwater, said a virtual trainer cannot track all three key aspects of conditioning: intensity, frequency and duration.
Some gamers say the cybertrainers make up for these shortcomings by enabling them to save the embarrassment of going to the gym. "I don't want a real woman staring at me doing exercises," said Chad Nelson, 34, from West Des Moines, Iowa, who plays combat games with Anna. But Mr. Nelson admits he can let his form go. "When I kick," he said, "I'm not controlling it."
Kinetic players also say the camera fails to register some movements, either because of background clutter or too little lighting. Other errors are merely distracting. Occasionally Maya will lift a weight through her breast, said Mr. Raphael, who writes a blog, www.videogameworkout.com.
The makers of Yourself!Fitness are working on a sequel, one that will do away with glitches and provide more gaming hooks so users don't get bored. The idea is to offer a dose of exercise that doesn't seem like medicine. "The fitness component isn't what is driving people," Mr. Lowenstein said. "It's the 'Matrix'-like experience."