The theories around psychological traits and somatotypes, or body build, are considered outdated. Yet, evidence exist that different body types tend to excel in different fields of sports and respond differently to various forms of exercise.

The three main body types are: Ectomorph, mesomoprh, and endomorph. All of us have bodies that are a combination of these body types. However, someone who is clearly at one of the the extreme ends will benefit from considering her body type when setting goals for muscle building or performance.

- are tall and slim

- have a narrow frame

- have long, slender limbs

- have little muscle and fat 

- have fast metabolism 

- are hard-gainers when it comes to muscle (and fat)

- are built for endurance sports such as long-distance running

If the goal is to gain muscle mass and strength, the ectomorph should:

- be sure to eat enough (large calorie surplus)

- not spend too much time on cardio

- focus on volume and intensity if gaining mass is the main goal

- have an athletic build

- have little to moderate body fat

- will gain muscle fairly easily 

- can be successful in a wide range of sports 

With a balanced diet and training program mesomorphs can easily gain muscle. As mesomorphs gain muscle relatively easily there is no need for excessive calorie surplus.

- have a softer, rounder body shape

- have a slower metabolism

- will gain muscle and fat quickly

- have a hard time losing fat

- can be successful in sports where strength and size are essential 

The endomorph gains mass easily, but must be careful with excess calorie consumption and spend a considerable amount of time on cardio in order to avoid gaining fat mass.