If you're working on your thighs just to trim them down, it's not going to work, says trainer Michelle Nevidomsky-Dozois, co-owner of Breakthru Personal Fitness Studio in Pasadena, Calif. But that doesn't mean you shouldn't work them. Instead, she says, you need to rethink your approach: Develop them. Developed muscles actually take up less space than the same amount of fat.

"The abductors and adductors, the outer and inner thighs, respectively, are relatively small, stabilizing muscles, "Nevidomsky-Dozois explains. "We need them for daily life - so we don't get injured." Once you switch to that mind-set, it's possible to get strong thighs overall that can help you to valance, make it easier to move laterally, and stabilize other movements.

Michelle Nevidomsky-Dozois understands that not all her clients are happy with their thighs, but she reminds them, "You can't spot reduce." You can, however, develop strong thighs to help you perform cardio activities like running and stair climbing more efficiently, which in the end helps you burn more calories. Nevidomsky-Dozois is also quick to tell her clients to stop working their thighs every day, which can cause injury and decrease exercise effectiveness. "Twice a week for two sets is plenty," she says.

To help you change your focus from thin to developed and functional, Nevidomsky-Dozois has developed some challenging moves. "These exercises are the type that people often don't do," she says. "They're excellent for building stability and balance." She starts with the wobble-board squat to work your stabilizing ability - and because it's fun. "It's a good warm-up because it recruits a wide variety of muscles," she says. "If you're not coordinated, put the board near a support and just stand instead if squatting." Once you're used to it, go for the whole move.

The other two exercises can be done in any order. If you're concerned that your leg won't be able to support the weight during the one-legged squat, do that one first, when your muscles are fresher, Nevidomsky-Dozois advises. For the cable lift, "Work your weaker leg first," she suggests. "We tend to work our stronger side first, but in this case, switch." That way, you'll be able to finish both legs before you're too tired.

1 [WOBBLE-BOARD SQUAT] Stand with your feet hip-width apart and centered on a wobble board. Maintain an erect posture, hips and shoulders square, and look straight ahead as you balance. Concentrate on actively using your inner thighs and upper hips to keep your knees aligned over your toes. After balancing, bend knees, lowering torso into a quarter-squat; focus on your hip and leg position and on maintaining your balance. Straighten legs and repeat. If you don't have a wobble board, you can do this move on a 2-by-4-foot piece of wood balanced over tennis balls cut in half. Strengthens both inner and outer thighs as stabilizers; also buttocks, hamstrings and quadriceps on the squat.

Keep your buttocks relaxed; focus on using your inner and outer thighs to help maintain alignment.

2 [ONE-LEGGED SMITH MACHINE SQUAT] Stand in a Smith machine with the bar across your upper back and shoulders. Unlock bar and move feet slightly forward. With chest up, shoulder blades pulled back, abs tight and a neutral lower back, turn legs out slightly from hips; lift one foot and touch it behind the other. Bend knee until you can't keep your heel in the floor or have trouble keeping knee over foot.. Return to starting position (don't lock knee). Do reps. Switch legs; repeat. Strengthens inner thigh and upper hip as stabilizers; also works quadriceps, hamstrings and buttocks.

Maintain knee and hip position by visualizing your right inner thigh and your right hip pressing down and out.

Focus on pressing working hip down as your leg arcs out and up.

3 [CABLE LIFT] Stand with your right side to a low cable pulley with the cuff attached to your left ankle. Adjust your distance so you are supported but still have a slight tension on the cable; hold the bar with your right hand for support, left hand one your hip. Keep your hips square and chest lifted, abdominals contracted and knees slightly bent. Maintaining torso and hip alignment, slowly lift your leg as one unit without rotating hips. Return to starting position. Do reps, then switch legs and repeat. Strengthens upper hip; also works inner and outer thigh of support leg stabilizers.

Muscle Mechanics These moves target your hip abductors (outer thighs) and adductors (inner thighs), which attach to your pelvis and thighbone. The main abductor, the gluteus medius (6), moves your leg away from your midline with help from the gluteus minimus (7) (beneath it) and four other muscles. Five primary muscles line your inner thigh to bring your leg toward your midline: the three of the adductor group (longus (3), brevis (2) and magnus (5)) and the pectineus (1) and gracilis (4).