The Scalenes are located on the front and side of your neck (i.e. in the anterior cervical spine - see image).
They often harbor trigger points with more diverse and peculiar symptoms than any other muscle tissue in the body. Hence, we called them 'mysterious'.
Pain in the Scalenes is often felt just about anywhere but the Scalenes themselves. Instead of your Scalenes, your arm or chest might hurt.
Scalenes are known to cause headaches, neck stiffness, random chest pain, and even rib tension and breathing tension.
There are 3 Scalenes: Anterior, Middle, and Posterior. They all flex the neck (chin down) when working together on both sides. When working on each side, they flex the neck to the side and rotate the head to the opposite side.
Putting focused pressure on a Scalene can send a sharp painful sensation into your arm, up the neck, or down into the chest. If you look at the attachments of these muscles, it can explain why the chest and the neck can get affected.
But the reason why the referral pain is so random and diverse is due to the high density of nerves running through this area. When nerves are impinged by tight Scalenes, they'll send neurological signals into most random places.
Also notice the subclavian vein and artery in the image. Both run under the Anterior Scalene.
When these muscles get tight, they are capable of pulling on the first rib so much that it starts to impinge the nerve bundles and affect the blood flow underneath the muscles.
What To Do To Relieve Tension and Stop Referred Pain from Scalenes
Neuromuscular Therapy. Nothing is quite as effective as NMT for Scalenes. Focused neuromuscular release of trigger points will stop the buildup of tension, get rid of nerve impingements, and free up the neck and chest blood flow.
Make sure to find a therapist who specializes in Trigger Point Release, NMT, or similar modality, and is very familiar with the anatomy of the cervical region. It's possible to cause serious harm in this area by compressing the nerves and arteries if the therapist does not have the necessary training.
Stretching the Scalenes and Strengthening movements of the neck are helpful to maintaining good range of motion and blood flow, but will not fix the tension, or treat the trigger points.