Achieving thinner thighs ranks high on the exercise priority list of most women.

In fact, it is the one area of the body women complain about the most, said Dega Schembri, an aerobics instructor and owner of Fit Physique Exercise Studio in Northwest Washington. "Women tend to gain weight in the outer thigh area, and they want to get rid of what they call their 'saddlebags.' "

Although spot reducing -- burning fat from one area of the body -- is not possible, toning or firming a specific muscle group is. "Muscle takes up less space than fat, and if you tone your muscles, you will have a sleeker look," Schembri said.

Two main muscle groups make up the thigh area -- the quadriceps and the hamstrings. The quadriceps are powerful muscles that straighten the front of the leg and prevent the knee cap from slipping out of alignment. The hamstrings -- located at the back of the thigh -- bend the knee and help swing the leg backward.

Developing strong thighs means strengthening both the quadriceps and the hamstrings, said Peter Van Handel, senior physiologist at the Olympic Training Center in Colorado Springs. "If you have very strong quads but weak hamstrings, that is not a good situation," he said.

Achieving the thighs of Tour de France bicycle champion Greg LeMond or record-breaking Olympic sprint star Florence Griffith Joyner won't happen overnight. It takes time and patience.

Fitness expert Kathy Smith recommends starting out slowly and using concentrated exercises for the thighs that will develop form and technique. In her "Ultimate Stomach and Thighs Workout" video, Smith focuses first on teaching the viewer proper body alignment and how to execute each movement before attempting more strenuous thigh exercises, such as one-legged squats and advanced lunges.

Some resistance training, in which people work against their own body weight or with additional weights, is needed to tone the thigh area. Cycling is one of the best ways to develop good thighs, said Rick L. Sharp, director of the Human Performance Lab at Iowa State University. Doing knee lifts with weights and squats are also helpful, he said.

Firming the thighs also means building muscle mass, and this can be very disappointing to women, Smith said. "If you are overweight, you will tone a muscle with a layer of fat on it and the leg will end up looking bigger."

Smith emphasizes the importance of exercising for general good health, not just focusing on the quest for thinner thighs.