Reducing the amount of time spent in a single posture is one of the most effective methods for reducing stiffness in the muscles of the shoulder and neck. "Spending long hours at your computer or on your phone can lend itself to stiffness and pain from immobility in your neck and shoulders," according to the physician Dr. Helfrich. "Take one to two minutes every hour to move your head from side to side to help stretch out the neck and shoulder muscles."