Body shapes have been classified into somatotypes of which there are three:
Endomorphs are characterised by the roundness and softness throughout their whole body. They are often referred to as having pear-shaped bodies. With their short limbs and rounded shape, they may be able to build muscle, although this will simply exaggerate their existing shape.
Ectomorphs are characterised by slim and lean builds. They are usually tall and skinny and may find it quite difficult to add muscle bulk. This is because their long lever lengths (limbs) may make it hard for them to lift heavy enough weights in order for them to achieve a progressive training effect without over-stressing the tendons and ligaments.
Mesomorphs are characterised by a body which has a high proportion of muscle. This body shape usually responds well to all types of training programmes.