If you're stuck in a workout rut or find yourself flat-out uninspired to get in shape, perhaps a fitness mismatch is to blame. "One size definitely does not fit all when it comes to exercise," says our mind-body fitness expert Ellen Barrett. A friend's "amazing workout" may be your recipe for boredom, just as what motivates you may fail to inspire her. The key to staying fit for life, our experts say, lies in pairing your program to your body type. You'll see the best results -- and have the most fun along the way.

Schools of thought in both the West and East (specifically, India's Ayurveda) put people into three camps: muscular/athletic, slender/quick, or curvy/steady. You probably lean toward one grouping, but "most people are hybrids," explains Barrett. "You'll often have both a primary and secondary type." Each category has its strengths, and the optimal fitness plan capitalizes on these while also helping you to balance out your weaknesses.

To find the one that best caters to your body type, identify yourself in the descriptions that follow. "You'll be much more likely to stick with a program that suits your individual needs," says Jennifer Kries, a Philadelphia-based Pilates instructor and creator of the Hot Body Cool Mind: The Life Force Power Workout DVDs. "You'll also build greater self-respect as you do." And that might be the best benefit of all.

Decide your body type and get your new customized workout:
Ectomorph: Slender (Energetic and Quick)
Endomorph: Curvy (Strong and Steady)
Mesomorph: Muscular (Driven and Athletic)

Text by Kate Hanley; photographs by Henry Leutwyler