When you open the front door during August and the humidity fogs your sunglasses, the heat blasts your brain and the air smells like dog breath, it's enough to fling even the most well-intentioned exerciser back to the couch.

Hot weather exercise can be more than just unpleasant, it can be downright dangerous, because heat can kill. Running or walking may be bearable in the evening or early morning, preferably in a well-shaded park. But when the thermometer tops 90 degrees and the humidity 40 percent, avoid outdoor workouts entirely -- unless you're in cool water.

This doesn't mean, however, that the dog days should trample your exercise habit. Dive into water workouts or bring your fitness routine indoors.

Now's a good time to join a gym or exercise class; buy a short-term membership to see if you like it. You can fitness walk at the mall, climb stairs in an apartment or office building or -- most convenient of all -- work out in your own home.

Here's some indoor exercise inspiration to get you through Labor Day.

Exercise machines. Consider renting or buying a treadmill, stair-climber, stationary bike, cross-country ski machine or rower. If you have one that has been doubling for a clothes rack, dust it off and try: Distraction. Television, music, reading, audio or videotapes, talking on the telephone/speaker phone or dictating can all make exercise time fly. (Get a headset for your telephone, but be sure the person you call won't get the wrong idea if you puff and pant a bit. If you huff and puff too much, you're working too hard.)

Pump light (2 to 5-pound) hand weights while you ride your stationary bike.

Set up a fan for extra coolness.Video games. Pull your stationary bike up to your Nintendo or bring your gold card to the fitness store for a stationary trainer that will electronically pit you against the best cyclists on the toughest courses in the world.

Jump rope. An excellent aerobic activity that burns 360 calories per half-hour, jumping rope is harder than it looks. If you can't jump rope continuously for 30 minutes, and few people can, jump for a minute or two, then march in place. Alternate jumping and marching, lengthening the jumping interval as you become more adept.

Wear well-cushioned shoes and jump on a forgiving surface, such as a wood floor that's not laid over tile or concrete. Remember to start slowly, warm up and cool down.

To pick the proper length rope, stand with one foot on the center. The ends of the handles should just reach your armpits.

Bench-step. The latest craze in aerobics classes is stepping up and down on a bench while you pump light dumbbells. Several companies manufacture step benches that range in height from about 4 to 12 inches. But you can also use any sturdy box or step stool, put on the music and move.

Workout videos. Check the TV listings for workout shows and tape them, or try one of these new videos:

SALSA-robics. Not just a hot sauce, salsa is a hot dance, and this new program based on Latin and Caribbean rhythms makes working out "mucho" fun. Taped on the beach in the Florida Keys, the video includes 28 minutes of singles routines and 31 minutes of couples routines, including one that's so spicy you'll know why they banned the lambada.

The shifting camera angles make it sometimes difficult to follow the excellent leader, Esther Gutierrez Sloan. But, then, there's no right or wrong way to salsa; you just move your body to the music. (Kultur, $19.95 plus $3 shipping, VHS and BETA, 1-800-252-6969.)

The FIRM Aerobic Workout with Weights, Volume 4. Finally a short, 42-minute workout from the folks who consistently get top marks from serious aerobic jocks. You'll need light, medium and heavy dumbbells, plus ankle weights and a step-up box. (Meridian Films, Inc., $44.95 plus $3 shipping, VHS and BETA, 1-800-THE-FIRM.)

Shape Up With Molly Fox. New York trainer Molly Fox has put her most popular workouts into this three-tape series: "Fat Burning," "Total Body Workout" and "Abs, Thighs and Buns." Each tape is about 45 minutes and costs $14.95; $26.95 for two; $34.95 for three, plus $2.50 shipping and handling per order. (Congress Video, 1-800-523-5503.)

Bodyworks appears on alternate Tuesdays.