It's irrefutable: Your body's blueprint is pretty much determined on the day you are born. Although you can change your body composition (the amount of fat versus the amount of muscle you hold on your body) with exercise and diet, your basic structure will always remain the same.

At first, this may seem like bad news. However, it should be a welcome relief from the pressure of endlessly trying to achieve a body for which you are not designed. There are three basic body types: the ectomorph, the endomorph and the mesomorph. Whatever your type, follow a workout that's designed to make the most of it.

* Ectomorphs are long, wiry and narrow. They generally have delicate bone structures and shoulders and hips that are approximately the same width. Accomplished long-distance runners, ballerinas and basketball players are often ectomorphs. (Michelle Pfeiffer, Whitney Houston and Heather Locklear are examples of in-shape ectomorphs.)

Weight training strategy: Build up muscle with 2 to 4 sets of weight training exercises per body part. Use a moderate-to-heavy weight that you can lift with good form for 6 to 10 repetitions. Consider doing a split routine where you work some parts of the body one day and then others the next.

Cardio training strategy: Your goal is to up your stamina and whip your heart and lungs into shape, so include cardio exercise 3 to 5 times a week. Aim for 20 to 40 minutes per session at a moderate-to-intense workout level.