The external intercostal muscles are a group of skeletal muscles located between the ribs on the outside of the rib cage.

Origin

They originate on ribs 1–11.

Insertion

insertion is on ribs 2–12.

In the respiratory system, the external intercostals is an inspiratory muscle.

Most often the respiratory system, more specifically, the inspiratory and expiratory muscles, are not thought to be trainable except through aerobic type activities.
This, however, is only partially true. The respiratory system muscles can also be strengthened with specific strength training exercises.

Volume 12 - The Respiratory System of our Kinesiology of Exercise Ebooks is a first for a book on strength training for the respiratory system.