If you're warming up to the idea of a home gym in your house or apartment, you're not alone. Retail sales of home gym equipment in America topped $5 billion in 2006, while 2007 sales are estimated to increase by an additional 3 percent, says the National Sporting Goods Association (NSGA) in Mount Prospect, Illinois.

While those dollar amounts are enough to get hearts racing, exercise physiologist Bob Greene, certified personal trainer to Oprah Winfrey and best-selling fitness author, cautions against impulsively buying expensive equipment for a home gym.

He says the first step to creating a personalised workout space is to have a fitness plan.

"Your doctor can really help you define what your fitness goals may be — whether it's rehabbing an orthopaedic condition or dropping weight," Greene says. "The candidate for a home gym needs to be self-motivated."

Being committed to an exercise plan means dedicating the space in your home to exercise, whether you're converting an outdated playroom or fixing up the basement.

"Since you may spend up to an hour every day working out, you really want to make your home gym a place you want to go," Greene says.

The gym inside Denise Austin's suburban Washington, D.C., home reflects her personality. Austin has sold more than 20 million fitness videos and DVDs and is known for her bubbly personality and high-energy workouts. Natural light floods her home gym through windows, while walls painted a soft peach colour give the room an airy, open feeling.

"It's so convenient to wake up in the morning and work out with my husband, Jeff," Austin says. "Your personal gym should be a place where you can exercise and just be yourself."

Austin advises anyone setting up a home gym to steer clear of the bedroom.

"When you enter that home gym space, you're there to work out," she says. "The only seat I have in my gym is on the weight bench."

Austin's gym has wood flooring, a mirrored wall, stereo system and television with DVD player. Her exercise equipment includes stationary bikes and a treadmill.

Greene says the treadmill is his favourite piece of cardiovascular exercise equipment, and American consumers agree.

NSGA spokesman Dan Kasen says US treadmill sales topped almost $3 billion last year, selling more than 4.7 million units. Some exercise equipment can be programmed to calculate pulse rate and the number of calories burned as you step, pedal or stride.

"We're becoming more health-conscious, and the technology in exercise equipment is appealing," Kasen says.

But don't be distracted by all the bells and whistles on expensive exercise equipment. Before you buy anything, your first investment should be time. Measure different exercise machines to see what will fit into your home gym space, and don't be afraid to try out machines in a showroom to see what equipment might work best to achieve your fitness goals.

Most exercise machines will allow you to modify the weights and difficulty, but choose equipment that isn't too complicated to alter. Before buying, make sure you understand the equipment's setup, guarantees and maintenance requirements. The best home gym equipment is backed by at least a one-year warranty.

If space is at a premium in your home, Greene and Austin suggest simple, lower-cost alternatives to expensive exercise equipment. No remodelling is required to use:

?A yoga mat, which provides a cushion for floor exercises and easily rolls up.

?Small free weights, which pump up strength training and can be kept on a bookshelf.

? An exercise ball, which aids balance and flexibility. These balls can be tucked away in a closet.

? A jump rope, which ups the heart rate. After skipping, you can easily store it in a drawer.

Austin finds motivation in her home gym by working out to music with a driving beat while breathing in fresh air through open windows.

Greene says if you enjoy your fitness routine, you're more likely to continue it over a lifetime. When commitment is waning, change your workout, Greene says.

"There's nothing like taking a walk in the great outdoors to complement what you do in the four walls of a home gym," he says.