There's no place like home: how to avoid exercise equipment rip-offs.

It's easy to find excuses for not exercising. It's too hot outside or too cold, too dark or too wet. There's not enough time, you're embarrassed to be seen "in shorts, you can't leave the baby, you just washed your cat.

When your motivation to work out needs a jump-start, few excuse-busters are as powerful as home fitness equipment. Convenient, private, and time-saving, home equipment allows you to walk a treadmill watching Dan Rather, read Proust while riding an exercise bike, or lift weights while Junior naps. Home exercisers are more likely to stick with their program than people who go to a class, says research from Stanford University.

That's one reason why Americans spent a record $3 billion on home fitness equipment last year, more than double the amount purchased just five years ago, notes the National Sporting Goods Association. And with an increasing array of fitness gadgets vying for consumers' dollars, it's easy to wind up so confused or intimidated that you plunk down hard-earned cash on a pricey gizmo that will wind up gathering dust.

"There's a huge market in used exercise equipment because too often, people buy something that looks good in an ad, then find out they hate using it," says Susan Kalish, executive director of the American Running and Fitness Association in Bethesda, Maryland. Be skeptical of advertising claims, she says, and always work out on a machine before buying it.

And remember that even the best, most reputable machine won't get you in shape unless you use it...as more than just a clothes hanger. Consider both your goals and your preferences, says Edmund R. Burke, associate professor of exercise science at the University of Colorado and author of The Complete Home Fitness Handbook (Human Kinetics, 1996, $14.95).

"If your goal is to boost your cardiovascular fitness or lose weight," Burke says, "consider a machine that will give you an aerobic workout and burn calories," such as a treadmill, stationary bike, stair climber, ski machine, or rower.

If your goal is to build strength, you'll want to buy resistance equipment, which can range from inexpensive elastic tubing or dumbbells to costly multi-station weight machines like the Soloflex.

The single most important piece of advice: Find something you like and can picture yourself using for at least 20 to 30 minutes, three or more times a week, for the rest of your life.

"One approach is to buy equipment that complements an activity you enjoy," Burke says. "If you like to walk or run but have trouble sticking with your exercise program when it gets dark or cold, a just what you need."

Or look for equipment that offers variety. For example, if you get a regular aerobic workout walking your dog every day, you may want to add a strength-training component by purchasing resistance equipment such as free weights. Or a runner might want to buy a stationary bike with movable handles to use on alternate days. The handles add upper-body conditioning and the bike provides a low-impact, aerobic workout.

For most people, cost is also a factor. Since low-end equipment is often poorly made, hard to use, and easy to break, be wary of the cheapest models. The best value is frequently in the mid-price range, and you can save money by shunning fancy electronics and decorator materials. For a real fitness equipment bargain, look for used equipment made by a reliable manufacturer. Or buy a $10 jump rope and a good pair of $50 walking shoes.

Here's a rundown of the four topselling kinds of home fitness equipment:

* Treadmills. Americans spend more on treadmills--$963 million in 1995--than on any other kind of home exercise machine. With prices ranging from $150 for non-motorized models to $4,000 for motorized ones, and features that can simulate everything from walking trails to running hills, the choices can be overwhelming.

Non-motorized, manual treadmills operate by having the user walk on the rubberized surface, which powers the belt. If the exerciser slows down, the belt slows down. On a motorized model, the belt continues at the same speed, forcing the exerciser to walk or run at that pace. In other words, you challenge a manual treadmill, but a motorized treadmill challenges you.

For manual treadmills, Burke recommends the NordicTrack WalkFit for around $600 and the Easy Strider by Ultrafit for about $360. But "for the serious fitness enthusiast," he says, "a high quality motorized treadmill--which will cost $1,000 or more--is a must." He likes Schwinn Cycling and Fitness's Home Trainer 615 for $1,900 and The Life Fitness 3500 at $2,350. But since picking a treadmill is such an individual matter that takes into account your size and whether you like to walk or run, he suggests trying different models made by quality manufacturers like Trotter, Life Fitness, Cybex, Precour, or Schwinn.

Several factors separate the high-quality treadmills from the pretenders. Check the amount of power delivered. If you're running more than walking, look for a motor with at least a 1.5 horsepower continuous duty rating. Also, a welded frame and deck construction is by far the most durable, since bolts and rivets will eventually rattle loose. Look for a panic button that will bring the treadmill to a rapid halt. Along with side or front rails, stop buttons can make you feel safer and more at ease.

* Abdominal Machines. In a nation obsessed with flat stomachs and "washboard abs," it's no wonder that the single most popular piece of exercise equipment has become the "ab machine." With names like the Ab Blaster, Abflex, ABShaper, and Ab Trainer, these gadgets promise to take you from flabbiness to fabulous. Last year, an estimated five million practically flew off the shelves.

At the relatively low cost of $30 to $200, an ab machine seems like an inexpensive way to carve out a chiseled midsection.

The catch? There's nothing you can do with an ab machine that you can't do without one. Plain old sit-ups and crunches done without any device can be every bit as effective at strengthening your abdominal muscles (see illustration). Some ab machines do support your neck and upper back, however, which can make an abdominal workout more comfortable.

As for the claims that ab machines can magically take your stomach from fat to flat: pure bunk.

"To lose a pound of fat you need to burn about 3,500 fat calories and not put them back by eating more fat," says orthopedic physical therapist Carol Hamilton of Frederick, Maryland. "This takes more than 4,500 repetitions for about seven and a half hours on an ab machine. Losing weight and slimming your stomach takes a combination of a balanced low-fat diet and regular aerobic exercise.

"Unless vou Dush yourself away from the table and engage in aerobic, calorie-burning activities, the ab machine will do little to trim your waistline."

But that doesn't mean the devices are worthless. "Perhaps the best reason for buying an ab machine is to help your motivation," says Hamilton. "The machine may be just the thing to get you started on crunches and other abdominal work, and lead you to a more complete exercise program."

* Rider/Gliders. Within the last several years, aerobic "riders" and "gliders" have become one of the hottest-selling fitness devices, with about three million sold last year. At a cost of about $200 to $250, these machines are touted as an almost effortless way to get fit.

But while rider/gliders can offer some benefits to beginners, they don't give people who are already fit much of a workout, according to a study by the American Council on Exercise (ACE), a not-for-profit organization that sets certification standards for fitness professionals.

For example: "Using the Fitness Flyer and Airofit air glider machine, the subjects, exercising at maximum effort, only reached a peak heart rate of 155 beats per minute, equal to a quick walk or slow jog," notes exercise physiologist Richard Cotton, editor-in-chief of ACE's FitnessMatters newsletter.

"On average, a moderately It male between the ages of 23 and 29, such as the subjects studied, should be able to reach a heart rate of at least 194 beats per minute during a peak-performance test."

Consumers who are already fit might be better off working out on a treadmill, reported a second ACE study, which monitored college-age women while they were using aerobic gliders and treadmills.

When the women performed the exercises recommended by the rider/glider manufacturers, they burned no more than half the calories that they did while using the treadmill.

ACE also expressed concern about the back pain reported by five out of seven participants after exercising on two types of rider/gliders--the Cardioglide and the HealthRider. "This finding is significant," the study reports, "given the fact that all the participants were young healthy females with no previous history of back problems."

* Weight Machines. If you've got the space and the money--typically between $1,000 and $2,500--a multi--station weight machine can be a great way to get strong. Quality equipment by manufacturers like Schwinn, Soloflex, and Trimax allows you to complete a workout in very little time by simply moving from station to station. And they can be safer than free weights because it's impossible to drop a weight on the floor--r on your foot--which eliminates the need for a spotter.

Before you buy, be sure to measure your floor space and ceiling height. And try every station to make sure you feel comfortable in each position. Make sure the cables, weightstraps, or levers move smoothly and quietly and that the padding on seats and armrests is comfortable.

Many purists prefer free weights--dumbbells and barbells--because they allow more variety in exercising. Also, they cost less. You can pick up a set, along with a weight bench, for a few hundred dollars. And free weights take up less space than a multi-station weight machine.

Novices should get instruction on either kind of weight equipment before beginning to work out. Improper technique can lead to injury...and that's one excuse you don't need.

RELATED ARTICLE: HOW TO DO AN ABDOMINAL CRUNCH

The best advice: Forget ab machines and simply do abdominal crunches. Here's how.

1. Lie on your back with your knees bent and your feet flat on the floor.

2. Cross your arms across your chest. or place your fingerstips lightly behind your head. Contract your stomach muscles and tilt your pelvis up, then slowly curl your head up, just until your shoulder blades lift off the floor.

3. Slowly lower back down. Repeats as many times as you can. Try to add a few more crunches each day. Be sure to exhale as you curl up and inhale as you release back down.

RELATED ARTICLE: A SHOPPER'S GUIDE TO BUYING HOME EXERCISE EQUIPMENT

Forget the claims made by scantily-clad hard-body exercise enthusiasts who promise thin thighs and bigger biceps to those who lay down their gold cards for the latest fitness fad.

"There is no one best kind of fitness machine," stresses exercise physiologist Richard Cotton, spokesman for the American Council on Exercise. "Consider what you like to do, what you find comfortable, what your goals are, the space you have, and what you can afford."

And remember: If exercise isn't fun, it won't get done. Before you buy, be sure to:

1. Try out different kinds of equipment to find something you like. Many gyms offer prospective members a free week, which provides a great chance to try out treadmills, stair-climbers, rowers, etc. Or consider purchasing a short-term gym membership to try working out on different machines.

2. Wear workout clothes and shoes when shopping seriously. Get on the equipment and test the feel and ease of use. If more than one person will be using it, make sure it's easily adjustable.

3. Buy from a reputable, knowledgeable dealer who specializes in fitness equipment and will assemble and service whatever you buy. Stay away from discount stores, which typically sell low-end equipment that is often poorly made, unsafe, and hard to use. If you need to shave dollars, choose a well-made model without fancy electronics or decorations.

4. Consider buying used equipment. Budget-wise consumers should check out fitness equipment resale stores like "Play It Again Sports" or look in the classifieds for good-quality used machines.

5. Find out about warranties, trade-ins, upgrades, and returns. A "free" 30-day trial may still cost a bundle in shipping--and aggravation--if you've got to box up the contraption and send it back.

6. Ask if the dealer will send a personal trainer to help you set up the equipment and get you started working out. Many will, either free or at low cost.

7. Be skeptical of claims made on "infomercials." Most have small-print disclaimers that say the product only does what it promises when used along with a diet and exercise program.

8. Beware of too-good-to-be-true claims like "melts inches from your waist." "Spot reducers" are all fakes, since it's impossible to lose fat from a selected body part. The only way to lose fat is to expend more calories than you consume. Even then, your body will decide where it wants to reduce fat. Exercising a body part will make it stronger, but if you don't burn enough calories, you're likely to wind up with strong muscles under a layer of fat.

Carol Krucoff is a freelance writer who specializes in health and fitness.