Q&A: How many weeks until you see results? What about swimming?

Q. I'm not overweight, but I'm flabby. For the last two weeks I've been walking 30 minutes on the treadmill four times a week and doing 15 minutes of weights. My sister says my workouts are too wimpy to help me firm up. Do I need to work out longer and harder to see results within a month?

A. "Visible results within a month might be an unrealistic expectation," says Leigh Crews, a trainer in Rome, Ga., and spokeswoman for the American Council on Exercise. You'll feel better and your cardiovascular fitness may improve, she says, but it usually takes six to eight weeks to see firmer muscles.

Your workout schedule is fine for a beginner, but you don't mention how hard you're pushing. A novice shouldn't venture into high-intensity cardio exercise, but twice a week you may want to go outside of your comfort zone for a few minutes at a time. For instance, after warming up for five minutes on the treadmill, alternate one to two minutes on an incline with five minutes of flat walking. Or, instead of an incline, do these "intervals" at a faster pace. (To avoid injury, don't try a faster pace and a steeper grade the same day.)

As for your strength training, 15 minutes is sufficient as long as you're lifting heavy enough weights and choosing effective exercises. "I recommend a split routine," Crews says. "Work your upper body one day and your lower body the next." For each exercise, Crews recommends doing one warm-up set, with relatively light weights, and then one heavy set, with enough weight to fatigue your muscles after eight to 12 repetitions. "After 12 repetitions, you should feel very glad to stop," Crews says. A trainer can help you choose the most efficient exercises for your 15 minutes.

Q. I find swimming very relaxing, but I don't feel like I'm getting much of a workout. Is swimming as good for cardio fitness and calorie burning as jogging or power-walking?

A. Swimming has the potential to burn as many calories as jogging and walking. "But the average person would have to work out at a much more demanding pace to match the calorie expenditures of jogging or walking," says Angie Proctor, executive director of the Aquatic Exercise Association in Nokomis, Fla.

For a 140-pound woman, swimming freestyle at a pace of 50 yards per minute (two laps) burns about 10 calories per minute, the same as running a 10-minute mile. However, while that 10-minute-mile running pace is within reach for most people, the equivalent swimming pace is faster than the typical untrained swimmer can maintain. Swimming at 25 yards per minute -- a fairly slow pace -- burns about 5.5 calories per minute, the same as walking at a 15-minute-mile pace.

To boost your fitness and calorie burn, include intervals in your workouts. After warming up for, say, 200 yards (eight laps in a 25-yeard pool), do a "set" of eight 50-yard intervals, swimming as hard as you can and then resting 10 seconds between each 50. Then rest for a couple of minutes and do a different set; for example, four intervals of 100 yeards, swimming at a moderate pace and resting 20 seconds between each100.

You can vary your strokes, alternate kicking with swimming and use equipment such as fins (which boost your heart rate and challenge your leg muscles) and hand paddles (for a tougher upper-body workout). Check out swimmeronline.com for sample workouts and advice on designing your own swimming routines.