The mid back serves as the base for your shoulder blades and many of your postural muscles of the upper body. It is the center or the core of the upper body. Ribs attach to the mid-spine and serve to protect vital organs. The larger muscles that originate or insert at the mid back, span most, if not all of the back. It serves to move the shoulder blades and contributes to movements in your neck and arms. The smaller muscles help with breathing and posture. Pain can sometimes occur when the structural alignment is out of place or muscles meant for the purpose of postures or movement are overused.
These stretches and exercises are also great to do on a daily basis. These muscles are commonly tight in most people. So my advice to you, do these exercises everyday, but especially if you're experiencing neck pain or headaches. Again, if you experience an unusual level of pain, go see your doctor!