It's worth remembering that trigger points in the psoas muscle (causing shortening of the psoas) can lead to adaptations in the scalenes, resulting in a short contracted state, thereby pulling up the ribcage and sometimes even affecting respiratory efficiency.

Clients may present with numbness in the anterior chest, the upper back, and the lateralanterior shoulder down the arm.

In many cases the pain may refer into the thumb and second digit.

The scalenes are a complex group of muscles with varying muscle fiber lengths, and therefore demonstrate the potential for many trigger points.

Excellent palpatory skills (and a lot of study and practice) may be required to successfully locate and treat these trigger points.