To generate power, you need mobility. To have mobility, you need stability. Proximal stability feeds distal mobility. Instability signals the brain and nervous system to put the brakes on power output because it feels threatened. A lack of stability is a threat to your nervous system.
When dysfunctional movement patterns exist, the brain will simply choose an easier alternate path to accomplishing a given task.
When the patient complains of pain in neck for long period of time and after doing certain activities e.g pushing an object) when they have poor core muscles, the SCM activate and gradually with the repetition of task the pain triggers.
Lie on your back with your leg straight. Now tie one of your legs to strong elastic band