Taken from Variables for Weight Lifting and Exercise © 2003 Anthony Sell - All Rights Reserved
Though there are many similarities between body types, there are also many variables that will differ from athlete. Some of these are environmental, others are inherited, others are developed. Some of these variables can be changed or worked around. Others will alter the level of realistic expectation.
Somatotypes are one method of classifying and discussing the potential of an athlete, as well as their nutritional and metabolic proclivities.
Essentially there are three somatotypes, the first is Mezomorph. The characteristics of a typical mezomorph include a tall bur evenly proportioned frame, with a large amount of muscle mass. Those who fall into this category tend to have an easier time gaining muscle than those with other body types.
Second, Ectomorph, characterized by a taller, lanky frame, generally thin and lean. Those with longer torsos and long limbs tend to fall into this category. Ectomorphs tend to be hard gainers, with respect to adding muscle mass and body weight.
Last, the Endomorph, has a more squat frame, rounder characteristics, with a larger ratio of fat to muscle. Those who are of a stockier frame, naturally barreled chested tend to fall into this category.
Most people will fall somewhere between some or all of these body types, as they are extremes that are merely useful for comparison. It is important, however, to consider your body type when tempering your expectations for physical gains.