FRIDAY, May 31, 2013 (HealthDay News) -- You're jogging at a steady pace, enjoying your favorite music through your headphones. Your breath is short and your heart is pumping. Your legs feel like they couldn't carry you any faster.
And then you hear the groan of a zombie over your right shoulder. It's sprint or be eaten.
The zombie apocalypse isn't upon you. You're just taking part in the latest fitness craze -- smartphone apps that make a fun and interactive game out of your daily workout.
Software developers are taking advantage of smartphones' advanced technology -- GPS, accelerometers, MP3 players -- to create "immersive" fitness games that appeal to both avid and reluctant exercisers.
It's part of an overall trend in the fitness industry toward making your daily workout "a fun experience rather than something you have to do," said Jessica Matthews, an exercise physiologist for the American Council on Exercise.
"We are attempting more 'play' opportunities as opposed to working out, basically getting people to move and having fun while they are doing it," Matthews said, noting that fitness instructors are being encouraged to include game play in group and one-on-one exercise as well.
One popular fitness game app, Zombies, Run!, places you in the role of a supplies runner for a walled community trying to survive against the walking dead.
During your run, the game's surprisingly complex story unfolds through your headphones. You "pick up" supplies for the community as you jog along. At certain intervals, you're alerted that zombies are nearby, and if you don't pick up the pace you'll have to pitch some supplies to keep from being caught.
The game doesn't end once your jog is over. After your workout, you can use the supplies you picked up during your run to fortify your community. The GPS statistics from your run are uploaded automatically to the game's website, so you can review your average speed and the estimated calories you burned.
Other fitness game apps place you in different scenarios.
BullDash, for instance, puts you in the middle of the running of the bulls in Pamplona, Spain, with immersive audio propelling you forward lest you receive a taste of the horns. Fit Freeway makes you the engine of a race car that you drive while on a treadmill or elliptical machine. The phone's accelerometer picks up the motion of your stride -- the faster you go, the faster your car goes. You tilt the phone left or right to steer.
Fitness apps that take a more social tack also are available. Teemo, Nexercise and Fitocracy all allow you to post your latest workout to share with friends. Some games have you work with friends to reach a common goal -- completing a relay race, for example -- while others encourage competition.
"That's another big area, having that social component," Matthews said. "Having social support of some kind is a critical factor in adhering to an exercise program. For some people, having that friendly competition or the feeling of being on a team can help them stay motivated."
What's more, the apps either are free or available at a minimal price of $2 to $4. Zombies, Run! is the most expensive at $7.99 for two "seasons" worth of episodes.
Donna Arnett, president of the American Heart Association, said there's good evidence already that gadgets like accelerometers can prompt interest in physical activity.
"I know when my accelerometer says I have 3,000 more steps to go to reach my daily goal, that motivates me," she said. "I would think the apps would work the same way. Anything we can do to motivate people is a good thing."
Dr. Stephen Ponder, an American Diabetes Association spokesman, said it remains to be seen whether these fitness games will have a lasting impact or prove a passing fad.
"If there are ways to use those devices to get people to move, I think that has a lot of potential," said Ponder, a pediatric endocrinologist in Temple, Texas. "The question is, can you see yourself using this indefinitely or would it need to change and morph and you'd need to have different games to keep your interest? For any kind of health technology, it needs to be something that people will put up with and use for an extended period of time."
The U.S. Centers for Disease Control and Prevention gives fitness recommendations for different age groups.