Rob Walter and his wife Lyn live in Fort Worth, Tex. Every Saturday, they attend 10 a.m. kettlebell classes, which their fitness instructor Ryan Shanahan conducts out of his Toronto home.

Despite the 2,000-odd kilometres between the two cities, the Walters have an easy commute; they only have to make it as far as their living room, where they are joined online by as many as 25 other students from North America, South Africa, Germany and Scotland. The couple simply switch on their iMac, which is hooked up to their 67-inch TV, and log on to the class through the online platform Powhow. On the screen, they can see Shanahan in one video box and other attendees following along in separate video boxes.

The Walters and their far-flung classmates are among a growing number of individuals who are turning to live online classes as a convenient and interactive home-exercise option. Attendees pay per class or sign up for monthly memberships and log on at scheduled times to follow their instructors in real time. Offered through sites like Powhow, EMG Live Fitness, and Face2Face Gym, online classes operate similarly to video conferencing, so participants can see and communicate with one another and instructors can offer immediate guidance and feedback.

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"This online stuff is just kick-ass," Rob Walter says. "It's like having a trainer in your own house."

Walter first got hooked on Shanahan's popular KettleWorX training program by using the celebrity trainer's DVDs, but since signing up last year after learning about them through Shanahan's Facebook page, he has found that online classes provide greater motivation – the workouts vary each time and the instructor's oversight means he can't slack off.

Shanahan, who has trained NHL, NFL and Olympic athletes and has worked on movies such as The Hulk and Max Payne, conducts all of his classes and personal training online. He and other trainers who offer live online instruction believe this medium is the next big thing in personal fitness, which they think will eventually make exercise DVDs obsolete. But for it to take off, clients will need to get accustomed to using the technology.

"The hardest thing to do is to get someone to try it for the first time," Shanahan says.

So far, the growth of these remote workouts looks promising. New York-based Powhow Inc., which describes itself as the largest marketplace of live webcam classes – music, art, and other lessons are available – has seen the number of instructors using its platform surge 100 per cent month-over-month (90 per cent of those instructors teach fitness and dance). Sales have jumped 30 per cent each month since it emerged from beta testing in November. The company now has more than 1,000 instructors offering 3,700 classes a month.

For many, convenience is the biggest appeal. In Bolton, Ont., Lee-Anne Simpson of the Revive Fitness Training and Wellness Centre initially offered live online sessions via Skype for frequent travellers and clients who moved away but still wanted to stick with her training method. She has since begun teaching a variety of classes, including cardio and interval training, yoga and pilates, through Powhow. Meanwhile in Steinbach, Man., trainer Tami Tyson says her live online bootcamp sessions – held on video chat site ooVoo – are a hit with new mothers who aren't able to leave home for a gym workout. People can seek out more obscure and specialized classes they can't find in their hometown.

Live one-on-one training sessions also save instructors from travelling to each individual client, which can mean lower fees. And they can be less invasive. Says Shanahan's personal-training client Lorynne Lofsky: "It's quite nice not having him come to the house because you don't need to worry about cleaning."

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Powhow chief executive Viva Chu says he anticipates the rise of virtual fitness studios. "What we're really trying to [dispel] is this notion that in order to be a trainer, you've got to actually set up a physical location," he says. Instead of paying hundreds or thousands of dollars in rent, instructors can pay as little as $30 a month to maintain a virtual studio and conduct classes remotely. They are also able to record their classes and offer them on-demand, which is much cheaper than producing DVDs.

Class sizes are limited only by the number of people who sign up, which translates to cheaper rates. Classes that would normally cost $20 at a gym typically cost $10 to $15 online. Many instructors offer monthly memberships, which are around $50 to $60, that give clients access to pre-recorded sessions on-demand as well.

Chu, however, doesn't believe online classes will pose a threat to gym-class attendance. As with online shopping sites like Zappos and Amazon, "what's ended up happening is that we're just actually consuming a lot more," says Chu. "What's likely to happen is … we'll end up taking more classes."

Live online sessions, for instance, allow people to experiment with new fitness methods, like Zumba or gyrokinesis, relatively cheaply and conveniently in their own homes, before making the effort to research studios and gyms.

Working out with others can promote friendly competition, but it can also make some people self-conscious, Simpson says. (For this reason, she gives them the option of turning off their webcams.) Also, she says, it can be disruptive when people sign in late.

Technical glitches, like echoes, feedback and delayed responses, are minor annoyances, Simpson says. But one of the biggest disadvantages is not being able to physically correct clients' postures or shift their positions.

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She adds: "Because they're not using mirrors, they can't really see themselves. They're not right there in the room with you…

"I think it's always going to better if it's in person," Simpson says. "I don't think it will ever replace that."