Q. I'm 24 years old and 5 feet 2 inches. I've lost 20 pounds over the last year and now weigh 108, which I'm happy with. I exercise five days a week for one to two hours and vary my workouts with running, weight lifting and yoga. The problem is, I don't look toned. I want to look firm, not flabby. Do I need to work out harder and more often to achieve this?

A. "No, you just need to work out smarter," says Dixie Stanforth, M.S., a lecturer in the department of kinesiology at the University of Texas, Austin. Quality is more important than quantity, particularly with strength training. Be sure to choose heavy-enough weights that when you hit your final repetition, you can't squeeze out one more.

You may also want to try periodization, a strategy that involves changing your routine every six to eight weeks. During one period, you might lift lighter weights and do 12-15 reps (still pushing to failure); the next period you might drop to six to eight reps with heavier weights. Then you might switch to moderate weights and to 10 reps. A trainer can fill you in on the details of periodization and teach you other techniques for boosting the intensity of your workouts.

Finally, keep in mind that developing muscle is a long process. When you lost those 20 pounds, you may have lost a lot of muscle along with fat, and it can take a long time to regain that muscle.