Treadmills, stair steppers, elliptical trainers—they leave you sweating and give your heart a great workout. But, if you want to reshape your body, you are going to have to work out a little smarter. Let's face it: sometimes we all need to zone out on a stationary bike with headphones and a magazine. But, some experts say the most effective workouts engage the mind, as well as the body.

Pilates (pronounced puh-LAH-teez) is a classic mind-body workout created in the 1920's by physical trainer Joseph Pilates. This workout may be the ideal antidote to a tired fitness routine. This method of body conditioning involves stretching and strengthening exercises done on mats and specially designed exercise equipment.

Even for beginners in great shape, the first Pilates mat class can be a humbling experience. Clare Dunphy recalls her first class, "I had been teaching fitness classes for 15 years, training teachers, and making videos, and I could not believe how little command I had over my body."

Although I walk and strength train regularly, I found myself struggling in Dunphy's morning mat class. Cues like "draw abdominals in and up," "press back into mat," and "lengthen the neck" seem to make sense on their own, but in concert, they were more than my body could focus on all at once. The moves are not complicated—Dunphy's demonstrations were simple and graceful—but they require an attention to our bodies that is unfamiliar to most of us. By working the body's core, including lower back, abdominal and gluteal muscles, the mat exercises challenge areas often neglected by traditional fitness routines.

The machine exercises are even more unfamiliar to many newcomers. Pilates machines can be found at most fully-equipped studios. Machines assist with resistance and support. Proper alignment is critical, so machine routines are generally taught one-on-one. From my first exercise on a machine, I could feel how I had been neglecting a whole dimension of fitness by focusing only on aerobic exercise and weights.

Such renewed body awareness is a vital part of Pilates. For many trainers and students, the lessons are simple: I can change my body with these exercises. And a great workout does not have to hurt.