If you only use the treadmill for walking and running, you haven't yet tapped into its full potential. The treadmill is a terrific tool for toning and sculpting shapely slender thighs. Squats, lunges and backward walking recruit multiple muscles in your lower body, and the incline feature ups the ante with an increased caloric burn. Before you begin, practice these moves on a non-moving surface, and wear supportive athletic footwear.

Blast Fat with Cardio

One key to slimming your thighs is reducing your total body fat. Exercise scientist Len Kravitz, Ph.D. of the University of New Mexico explains that consistent and progressively challenging aerobic exercise makes you a better fat burner -- and exercising at higher intensities dramatically increases the amount of calories burned in a single session. To increase exercise intensity using a treadmill, you have three options: Increase speed, ramp up the incline, or combine the two by walking or running faster at a higher grade. For optimal fat burning, the American College of Sports Medicine recommends 250 to 300 minutes of aerobic exercise weekly.

Lunge for Luscious Legs

Lunges target all the major muscles of your legs, and should be a staple of your thigh-reducing program. A 2006 study conducted at California State University, published in "Medicine and Science in Sports and Medicine," found that long-stride lunges like those performed on an inclined treadmill maximally activate your quadriceps, hamstrings, gluts, calves and inner and outer thigh muscles. Set your treadmill on its lowest speed and highest incline level. Grasp the safety bar with both hands. Step forward with one foot, landing on your heel as you bend your forward knee. Allow your rear knee to dip toward the treadmill deck. Rise out of your lunge as your forward foot travels beneath your knee and step forward with the opposite foot. Continue for two to five minutes.

Squat for Sleek Thighs

Like lunges, the California State University study found squats to be effective for recruiting multiple leg muscles. For thinner thighs, take squats to a new level by setting your treadmill at its lowest speed and highest incline. Facing sideways to the console, grasp the side rail with both hands and take a large step to the side with your uphill leg, planting your foot firmly with your weight on the heel as you sit into a squat. Rise as your legs come together, propelling yourself upward in a hop, and landing in a squat. Continue for two to five minutes.

Back Up for a Bodacious Bottom

Walking backward on an incline was found to significantly recruit muscles in the quadriceps, hamstrings and calves in a study published in the "Journal of Orthopedic and Sports Physical Therapy." Keeping the treadmill at its lowest speed and highest incline, face backward gripping the side rails for balance. Walk backward in a toe-to-heel foot pattern, fully extending your knees with each step. Do not support your bodyweight on the side rails. As you become adept at backward incline walking, increase the speed by small increments to increase your caloric burn.